Market B^

G

and other

Subtropical Fruits

Agriculture Handbook No. 398

áffi

Agricultural Research Service

UNITED STATES DEPARTMENT OP AORIGULTURE
34391.8

Preface

This handbook is a revision of Miscellaneous Publication No. 498,

"Market Diseases of Fruits and Vegetables: Citrus and Other

Subtropical Fruits,'' by Dean H. Rose, Charles Brooks, C. 0,

Bratley, and J. R. Winston, issued June 1943 and reissued April

1955 with no change in text. This is one of a group pertaining to

market diseases of fruits and vegetables. The publications are designed to aid in the recognition and identification of pathological

and physiological defects of economic importance affecting fruits

and vegetables in the channels of marketing, to facilitate the

market inspection of these food products, and to prevent losses

from such defects. Other publications in this group are—

MISCELLANEOUS PUBLICATIONS

98. Market Diseases of Fruits and Vegetables: Potatoes. Revised January 1949. [Out of print.]

228, Market Diseases of Fruits and Vegetables: Peaches, Plums,

Cherries, and Other Stone Fruits. Revised February

1950. [Out of print.]

AGRICULTURE HANDBOOKS

28, Market Diseases of Tomatoes, Peppers, and Eggplants. Revised February 1968,

155. Market Diseases of Beets, Chicory, Endive, Escarole, Globe

Artichokes, Lettuce, Rhubarb, Spinach, and Sweetpotatoes. April 1959. Reprinted May 1967.

184. Market Diseases of Cabbage, Turnips, Cucumbers, Melons,

and Related Crops. September 1961.

189, Market Diseases of Grapes and Other Small Fruits. November 1960,

303. Market Diseases of Asparagus, Onions, Beans, Peas, Carrots, Celery, and Related Vegetables. September 1966.

371. Market Diseases of Apples, Pears, and Quinces. 1971.
Market diseases

of

Citrus

and pther

Subtropical Fruits

Ä\

By JOHN J.^^UOOT^'msmreft plant pathologist,

LAURIE G.H.OVCK, i<íe8earek plant pathologist,

and

HOWARD B. JOHNSON, iennëTly research plant pathologist,

Market Quality Research Division

Agriculture ^andbook^o. 398 ^

Agricultural Research Service

yPiJTEB,STATES.DEPARTMENT (jtF AGRICULTURE. )

Washington, D. C. •)' Revised, May 1971,

For sale by the Superintendent of Documents, U.S. Government Printing

Office, Washington, D. C. 20402 — Price 70 cents

Contents

Page

Introduction 1

Citrus fruits:

Aging (stem-end rind breakdown) 2

Alga spot 3

Alternaría rot of lemons and black rot of

oranges 4

Ammoniation (See Exanthema.)

Anthracnose 6

Armored scale injury 7

Aspergillus rot 8

Black pit 8

Black rot of oranges (See Alternaría rot,)

Blue-mold and green-mold rots 9

Botrytis, or gray-mold, rot 13

Brown rot 14

Chewing-insect injury 16

Chilling injury 16

Albedo browning 17

Brown staining 17

Membranous stain 17

Oil-gland darkening 18

Pitting 18

Watery breakdown 18

Citrus rust mite russeting 19

Cottony rot 21

Creasing 21

Endoxerosis (internal decline) 22

Exanthema (ammoniation) 23

Freeze damage 24

Postharvest freezing 25

Freezing on the tree 25

Fusarium brown rot 27

Granulation 28

Gray-mold rot (See Botrytis rot.)

Green-mold rot (See Blue-mold rot.)

Internal decline (See Endoxerosis.)

Melanose 29

Modified atmosphere injury 30

Oil-gland darkening (See Chilling injury.)

Oil spotting (Oleocellosis) 31

Phytophthora rot (See Brown rot.)

Pitting 32

Pitting of freshly harvested fruit 32

Storage pitting 32

Puffiness 33

Scab 34

Sclerotium rot 35

Septoria spot 36

Sour rot 37

Stem-end rind breakdown (See Aging.)

Stem-end rot 38

Stylar-end breakdown 41

Sunburn 41

Thrip injury 42

Trichoderma rot 43

Water spot 44
Contents—Continued

Page

Citrus fruits-—Continued :

Watery breakdown (See Chilling injury.)

Wind scarring 45

Miscellaneous spotting and discoloration 45

Avocados :

Anthracnose (Black spot) 46

Avocado scab 47

Black spot (See Anthracnose.)

Blotch (See Cercospora spot.)

Cercospora spot (blotch) 48

Flesh darkening 49

Chilling injury 50

Heat injury 51

Rhizopus rot 51

Stem-end rots 52

Bananas:

Anthracnose 53

Botryodiplodia fruit rot 55

Chilling injury 5T

Crown rot 58

Pitting 59

Speckle 60

Thielaviopsis stalk rot 62

Figs:

Alternaría rot 63

Aspergillus black-mold rot 64

Blue-mold rot 65

Cladosporium spot 65

Endosepsis (soft rot) 66

Gray-mold rot 67

Soft rot or watery soft rot 67

Souring 68

Splitting 68

Sunburn 69

Watery soft rot (See Soft rot.)

Lychees:

Browning 69

Mangos :

Anthracnose 70

Chilling injury 71

Stem-end rot 72

Papayas:

Anthracnose 73

Stem-end rot 74

Pineapples:

Black rot 74

Brown rot , 77

Physiological breakdown 78

Pomegranates 79

Blue-mold rot (See Pénicillium rot.)

Gray-mold_ rot 80

Heart rot 80

Internal breakdown 80

Pénicillium, or blue-mold, rot 81

Splitting and cracking , 81

Sunscald or sunburn , 81

Literature cited , 82

IV
Market Diseases

of Citrus

and Other Subtropical Fruits

By JOHN J. SMOOT, Research Plant Pathologist; LAURIE G. HOUCK, Research

Plant Pathologist; and HOWARD B. JOHNSON, formerly Research Plant Pathologist; Market Quality Research Division, Agricultural Research Service

INTRODUCTION

Market diseases of fruits and vegetables are those that develop

during the process of marketing. Marketing includes the harvesting, grading, and packing of the crop, its transportation to market,

its storage at shipping point or at the market, and the various

handling operations required to move it from the wholesale

dealer to the retail store and the ultimate consumer. During

any of these operations the product may be subjected to conditions that impair its appearance and food value and render it

liable to attack by decay-producing organisms or physiological

breakdov^n.

The fruits discussed in this publication, like all other fruits

and vegetables, are susceptible to invasion by bacteria and fungi

at bruises and skin breaks. Hence, it is of prime importance

that they be handled as carefully as possible at all times. Clipper

cuts, fingernail scratches, injuries caused by packinghouse machinery, packing bruises, and damage caused by rough handling

in transit and on the market are all sources of danger. This is

especially true if the places where the fruit is packed, stored,

or offered for sale are not kept free of rotting fruit and other

infectious material. These injuries, as well as those caused by

insects, must all be considered when judging the storage or

shipping quality of the fruit or its likelihood of maintaining its

quality until it is consumed.

Temperature and humidity directly affect the development of

decay in fruit. They should have the critical attention of those

who ship or store fruit and of those who attempt to determine
2 AGRICULTURE HANDBOOK 398, U.S. DEPT, OF AGRICULTURE

why a given lot, at any stage in marketing, shows decay or other

deterioration. Too low temperature may freeze the fruit, or it

may cause only chilling injury; subtropical fruits are particularly

susceptible to such injury. Too high temperature favors decay

and may cause undesirable color changes. High humidity favors

the growth of fungi. Low humidity causes loss in weight and

possibly shriveling, especially if temperatures are high. For all

of these reasons, the management of storage rooms for citrus

and other subtropical fruits and the choice of conditions under

which to ship them to market, whether under refrigeration or

under ventilation, are not likely to give the best results unless

based on an intelligent use of all available information concerning

the market diseases of those fruits.

CITRUS FRUITS

Aging (Stem-End Rind Breakdown)

Occurrence, symptoms, and effects

The term ''aging'' or stem-end rind breakdown refers to a

condition sometimes found after harvest on most citrus fruits^

but chiefly on oranges, grapefruit, and tangerines. In this disorder, the rind around the stem button or elsewhere on the upper

part of the fruit wilts and shrivels, usually accompanied by a

collapse of outer rind tissues. This is a physiological condition,

apparently caused by the loss of water from the fruit. The

affected areas may turn brown, and the oil glands may collapse

(pi. 6, A and B). Under severe conditions with overripe fruit,

aging may be apparent before harvest. In examining fruit after

a storage or holding period, it is sometimes difficult to be certain

whether brown sunken areas are pits or aged spots. Generally,

these spots are called aging if they occur around or near the stem

button, and pitting if they occur around the equator or lower

part of the fruit. Spots in the latter locations are usually smaller

and more sunken, but they may coalesce to form large discolored

areas.

Fruit that shows extreme symptoms of aging, accompanied by

browning, usually has an off-ñavor. Similarly affected fruit may

be invaded by stem-end rot or other fungi which cause the fruit

to decay.

Another condition, similar to aging, is found late in the season

on tangerines and oranges. Minute cracks develop in a roughly

concentric pattern in the rind around the button. These cracks
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 3

may develop on normal-colored rind, but later the affected area

may develop a tan-to-brown corky appearance. This condition

is commonly observed on fruit on the tree, but symptoms intensify

after harvest.

Causal factors

The actual cause of aging is not known. The incidence varies

considerably from season to season and from crop to crop.

It is more prevalent on fully mature or overripe fruit. Several

factors tend to increase or aggravate symptoms in fruit prone

to age. These include delay between harvesting and packinghouse handling, excessive brushing, and low humidity during

holding before packing or in storage. Heated solutions used in

washing or in the "color add" process may also increase aging.

Control is best obtained by avoiding as many of the above factors

as possible. Varieties and crops known to be weak should be

handled as carefully and promptly as possible.

(See 56, 61, 87, llJf,, 116, 201, 208, 209.) ^

Alga Spot

Cephaleuros virescens Kunze

Alga spot and blight is a disease of citrus and many other

subtropical fruits grown in areas of warm temperatures and

high humidity and rainfall. In the United States it is most common in the southern part of Florida. It is most common on lemons

and limes and to a less extent on oranges and grapefruit, but

the problem is seldom serious. It does not originate on fruit

after harvest.

Damage results not by parasitism but by growth and expansion

of the algal tissues on the host tree, causing bark on the twigs

and smaller branches to crack and scale. Citrus fruits and leaves

may also be spotted by the superficial growth of algal colonies.

The spots on the fruit are slightly raised, nearly circular, and

up to a quarter inch in diameter. Under a hand lens, they are

moss-like in appearance.

Cause and control

The causal organism for algal disease is Cephaleuros virescens

Kunze, a filamentous green alga which sometimes associates with

^ Italic numbers refer to Literature Cited, pages 82 to 101.
4 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

fungi to form a lichen. The disease can be readily controlled by

maintaining good tree vigor, by good air drainage, by pruning

out of diseased branches, and by spraying with a copper fungicide.

(See 4, 76, 136; U7, 20l\ 208,283.)

Alternaría Rot of Lemons and Black Rot of Oranges

Alternaria citri Ell, & Pierce

Occurrence, symptoms, and eflf^îts

Alternaria rot of lemons and black rot of oranges, grapefruit,

and tangerines are caused by the same fungus {Alternaria citri).

Alternaria rot, found in lemons from all producing areas, is

sometimes an important storage and market disease. Before

present control measures were developed, Alternaria rot was

second in importance only to the green and blue pénicillium rots

on lemons*

Black rot of oranges and other species is a widely distributed,

usually minor, rot found in fruit from all citrus-growing areas.

Only occasionally is it prevalent enough to cause significant

losses in fresh fruit. The rot is important in fruit destined for

processing, since infection of 2 to 3 percent of the fruit is

sufficient to produce off-flavored juice.

Spores of the alternaria fungus may be found on or under

the buttons of almost all lemons, even very young fruit in the

orchard. Infection usually occurs through the button tissues,

but not until after the lemons are harvested and in storage. The

xot affects the central core and stem end or may occur as a

stem-end rot. First, usually, the buttons turn brown, then a slowly

developing pinkish to light-brown discoloration proceeds along

the vascular tissues of the central core, and to some extent in

the inner tissues of the rind, without at first visibly affecting

the exterior surface. Later the fungus breaks down the fruit

interior to a slimy, lead-brown mass, and grows outward to the

surface. There a dark-colored area becomes apparent, increases

in size rapidly, and develops a lead-brown color. Eventually the

entire rind breaks down (pi. 1, E),

Oranges, grapefruit, and tangerines may be infected by the

alternaria fungus (black rot) in the orchard or during storage.

In the orchard young, green, physiologically weakened fruit is

susceptible. Entry points for infection are the button or stem

end (pi. 1, A), the stylar end, and peel wounds (pL 1, B), Navel

oranges are usually invaded through the stylar end. Infected
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 5

fruit may color prematurely and drop from the tree, or it may

appear sound and remain on the tree. In the latter case, the cut

fruit shows an internal, rather solid, black rot at either the

stem or stylar end (pi. 1, C). Later, during storage and transit,

the rot reaches the rind surface, causing a tan discolored spot

or spots that enlarge and usually turn dark brown or black

(pL 1, D). The spots eventually become covered with gray-toblack fungus mycelial growth. The absence of early external

symptoms of alternarla decay makes detection at the packinghouse extremely difficult.

Causal factors

Lemons of low vitality are most susceptible to alternarla rot.

Such fruit includes that which is overripe, is held in storage too

long, or is weakened by such orchard conditions as cold weather,

drought, sunburning, dry winds, and internal decline.

Black rot of oranges, grapefruit, and tangerines infects physiologically weakened fruit. This classification includes young green

fruit weakened by improper fertilization or unfavorable weather

conditions and mature fruit weakened by long storage.

Control measures

Freshly picked immature lemons are resistant to growth of

the alternarla fungus in peel wounds, while ripe lemons are not.

Infection usually occurs through the button, but it is not until

the button tissues weaken and die that the fungus is able to

gain entry into the lemon. The length of time lemons can be held

in storage before button strength declines depends upon the stage

of maturity when stored, the time of picking, the year, and the

conditions in storage.

Alternarla rot is controlled or delayed by applying 2,4-dichlorophenoxyacetic acid (2,4-D) to lemons in the packinghouse as part

of the washing before storage. Buttons of 2,4-D-treated fruit stay

green longer during storage than buttons on nontreated fruit. By

prolonging button life, infection of the lemon by the fungus is

delayed.

Direct chemical control of the alternarla fungus on citrus

fruits has not been successful. Fungicidal treatments effective

against pénicillium and stem-end rots provide less than adequate

control. Fortunately, black rot of oranges and grapefruit is not

usually important on the market unless the fruits have been

held in prolonged storage. Disease development is greatly reduced

under refrigeration. The fungus develops rather slowly at tern-
6 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

peratures below 50° F., but some growth occurs even at 32°

in oranges and grapefruit after 8 to 10 weeks.

(See 17;Jf8, 57, 59, 76, 90, 100, 110, 129, 131, 136, H7, 201,

208, 209, 255, 256, 257, 258.)

Anthracnose

Colletotrichum gloeosporioides (Penz.) Sacc,^

Occurrence, symptoms, and efifects

Anthracnose attacks all citrus fruits on the tree, in the packinghouse, and on the market as well as in storage. It is a serious

disease of tangerines, tangerine hybrids, and certain other mandarin fruits in Florida that are harvested early in the fall when

long periods of ethylene degreening are required. The decay on

these degreened fruits may start at the stem end or on the side

of the fruit. It develops rapidly and may involve the whole

fruit. The decay is silvery-gray at first, changing to a leathery

brown (pi. 1, G). On round oranges, grapefruit, and lemons,

it is usually of minor importance. It occurs in fruit from weak,

unhealthy trees, in overripe or slightly damaged fruit, and in

fruit that has been stored for long periods of time.

Aflfected fruits may have one or more brown-to-black spots

ranging up to a half-inch or more in diameter (pi. 1, F). These

spots start as bruised or otherwise injured areas, which are

invaded by the causal fungus. The spores at first are a pink mass

that can be observed with the naked eye or hand lens. After

exposure to the air they discolor and appear as brown-to-black

spots. The affected area originally involves only the rind. It is

sunken, with a definite line of demarcation between healthy and

diseased tissues. Anthracnose, in the advanced stages, penetrates

deeply into the flesh and develops into an actual rot. If it occurs

at the stem end of the fruit, the affected area is firmer and drier

than stem-end rot, and the core region is gray-to-black, fading

through pink to the normal color. Blackening of the segment

wall is less pronounced than with alternarla black rot.

Anthracnose is attributed to infection by the fungus Colletotrichum gloeosporioides. Other species of Colletotrichum associated

with field diseases of citrus trees may be involved under certain

' Perfect stage, Glomerella cingulata (Ston.) Spauld.. et Schrenk.
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 7

conditions. The fungus is a secondary invader. Injury to twigs

and young growth by drought, freeze damage, poor soil conditions, and other factors weaken the trees. In the resulting

dead growth the fungus lives, grows, and carries over from one

year to the next. From this source the spores are spread to the

fruit by winds, rain, and insects. The fungus gains entrance

to the fruit at pits, mechanical injuries, or dead buttons. Except in mandarin-type fruits that have been subjected to long

periods of ethylene degreening, the disease rarely develops until

the fruit is quite ripe.

Control measures

Control of anthracnose depends on harvesting the fruit at

prime maturity. This avoids the necessity foi* prolonged degreening of immature fruit and eliminates the overripe fruit which

is more subject to decay than fruit of prime maturity. Control

depends also on careful handling, the shipping of strong, firstquality fruit, and the avoidance of unduly long storage. Temperatures below 50'' F. would prevent development of the rot

during the usual transit period. Pruning and the use of good

cultural practices maintain the trees in good healthy condition

and reduce the excessive accumulation of dead twigs that may

harbor the fungus. Presently approved fungicides are not effective in eliminating anthracnose in fruit that has been mishandled

and made susceptible to decay.

(See 76, 136, 147, 201, 206, 208, 209, 2Í6, 251, 279.)

Armored Scale Injury

Several scale insects are pests to citrus trees. They infest

the leaves, twigs, trunks, and fruit. They may cause serious

damage to the trees and degrade the fruit for fresh market.

The insect injures the fruit directly by feeding. On nearly ripe

fruit, scale injury has a tendency to delay degreening (pi. 5, B)

or to prevent uniform distribution of carotenoid pigments in

peel of highly colored fruits (pi. 5, C). The scales are so firmly

attached to the fruit that they are removed only with great

difficulty by the washer brushes in the packinghouse. As a

result, scales are very often seen on fruit at the market.

The armored scales are characterized by a waxy shell, which

is secreted by the insect but is not actually a part of it. This

shell, which is enlarged as the insect grows, is what is seen on

casual inspection.
8 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

The scales most frequently observed on the fruit include California red scale, Aonidiella aurantii (Maskell) ; chaff scale,

ParlatoTia pergandii (Comstock) ; Florida red scale, Chrysomphalus anonidum (L.) ; Glover scale, Lepidosaphes gloverii (Packard) ; purple scale, Lepidosaphes beckii (Newman) ; yellow scale,

Aonidiella citrina (Coquillett) ; and others. These scale insects

can be controlled by an approved spray schedule in the orchard,

(See 4, 31, 62, 88, 147, 201, 208.)

Aspergillus Rot

Aspergillus niger v. Tiegh., Aspergillus spp,

Aspergillus rot is of minor importance. It is not often seen

except on fruit held at high temperatures. This decay is caused

by several species of the fungus Aspergillus, the most common

being A. niger. It has been reported on fruit from most citrusproducing areas.

The rot is at first light-colored, watersoaked, very soft, and

easily punctured by light pressure with a finger. The rotted area

becomes sunken and darker. Later it is profusely covered with

masses of black spores (pL 1, H).

The decay appears to spread between fruit by contact at

medium to fairly high temperatures. On citrus fruit held at high

temperatures and infected with a mixture of decay organisms,

A, niger usually overgrows the other organisms on oranges, and

Geotrichum candidum (sour-rot fungus) predominates on lemons

(p. 37).

Aspergillus rot is prevented by holding fruit at recommended

temperatures and by many of the same methods used for control

of blue and green molds. (See control of blue and green molds,

p. 11.)

(See 13, 136, 19^, 208, 231.)

Black Pit

Pseudomonas syringae van Hall

Black pit of citrus fruit has been found in nearly all citrusgrowing regions except Florida, Brazil, and tropical areas with

high temperatures. In the United States, it is more common

in central and northern California than in other areas, but even

there, it is a serious problem only 2 or 3 years in a decade. Black
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 9

pit is rarely found in the market, because diseased fruit are

easily recognized and removed in the packinghouse.

Pseudomonas syringae, the bacterium causing black pit, is

distributed widely. It also causes citrus blast, a disease of citrus

leaves and twigs, as well as diseases of many other plants. Lemon

fruit is particularly susceptible to damage by this bacterium,

but orange and grapefruit trees are more often attacked on twigs

and leaves (citrus blast).

Black pit appears as brown to black-colored, sunken rind spots

or lesions ^4 to 1/2 inch in diameter, which penetrate the oilbearing and inner white layers of the peel. The spots may consist

of many small pits or specks. Black pit lesions may enlarge in

storage (pi. 3, H).

Since cool and moist weather favors development of the bacterium, most damage occurs in winter or early spring after

heavy rains. The organism enters fruit at thorn pricks or other

injuries caused by wind or hail. This disease is of minor importance. Preventive measures are not ordinarily considered

necessary.

(See 27, 75, 76, 77, 186, 11^6, 166, 208, 20U, 208, 209, 2U0,

2kl, U2, 261.)

Blue-Mold and Green-Mold Rots

Pénicillium italicunt Wehmer and P. digitatum Sacc.

Occurrence, symptoms, and effects

Blue-mold rot, caused by Pénicillium italicum, and green-mold

rot, caused by P. digitatum, are also known as pénicillium rots.

They are probably the most common of all the postharvest

diseases affecting citrus fruit. They occur in all parts of the

world where citrus is grown. They may attack the fruit on the

tree, in the packinghouse, in transit, in storage, and on the

market. Green-mold rot is more prevalent and important than

blue-mold rot. It sometimes accounts for up to 90 percent of

decay in transit, in storage, and on the market. Blue-mold rot

on fruit is more common in storage than in transit.

In an early stage both diseases appear as soft, watery, slightly

discolored spots about i/4 to y% inch in diameter. This stage is

called **pinhole rot.'' If the temperature is favorable, the spots

enlarge to li^ to 2 inches in diameter within 24 to 36 hours.

They are then sometimes known as ''blister rot.'* Soon after this
10 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

stage is reached^ a white mold begins to grow on the rind surface,

starting from the center of the blistered area. When this mold

colony has grown to an area of 1/2 to 1 inch, it starts producing

spores. At room temperature blue mold grows more slowly than

green mold and produces fewer spores.

In green-mold rot the sporulating part of the fungus growth

has an olive-green color, usually surrounded by a broad zone

of white mycelium, ahead of which is an indefinite watery band

of softened rind (pi. 2, A). In blue-mold rot the sporulating

area is blue, surrounded by only a small band of white mycelium

at the outer edge (pi. 2, ß), and there is a definite band of watersoaked rind just ahead of the mycelium. Blue mold sporulates

on the surface and also in the ñesh, sometimes reaching the

center of the fruit. Green mold sporulates predominantly on

the surface. If fruit wrappers are used, they adhere closely to

fruits rotted by green mold but not to those rotted by blue mold.

Under dry conditions, the molded fruit may shrink and become

mummified. Under moist conditions, other organisms such as

secondary fungi and yeasts enter the fruit and reduce it to a wet,

soft mass.

Further losses are caused when healthy fruit is soiled by mold

spores from the rotting fruit and must be repacked.

The green-mold fungus produces ethylene, a gas which increases fruit respiration, hastens rind coloring, and accelerates

button (stem-end) loss of healthy fruit. This ethylene production

reduces the storage life of healthy fruit in the same container or

even the same room with fruit infected with green mold, since

only small amounts of ethylene are necessary to stimulate these

processes.

Causal factors

Most of the damage from these rots shows up after the fruit

leaves the producing region, but it seems to be correlated with

weather at time of harvesting and packing. Fruit picked and

handled during wet, humid weather is more prone to decay than

fruit harvested under more favorable conditions.

The chief factor that favors the development of these rots is

mechanical injury to the rind, since both causal fungi enter

readily at such injuries. Skin breaks may result from careless

harvesting and packing methods, from rough handling in transit,

or from shifting and breakage caused by improper stowage of

the load. Blue mold is also able to grow from rotting fruit through
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 11

the uninjured skin of healthy fruit and for this reason is often

called blue-contact mold.

An important factor influencing the development of these rots

is temperature. Both molds grow best around 75° F. and are

slowed by lower temperatures. Storage at 59° delays development

of the decay about 5 or 6 days. Storage at 50° adds a further

5 or 6 days to the salable life of the fruit. At 40° to 45° the

development of both molds is practically negligible during the

ordinary handling period for citrus fruit. In overseas shipments

or in extended storage, both molds will eventually rot fruit

held at this temperature range. Blue mold develops slowly at low

temperatures that more completely inhibit green mold. Low

temperatures of 32° to 34° usually hold these rots in check during

short storage periods, but these temperatures may cause rind

pitting or internal physiological injury to fruit and should not

be used unless specifically recommended.

Control measures

The control of blue-mold and green-mold rots depends most

of all upon careful handling throughout the harvesting, packing,

and marketing processes. The fruit should be kept as free as

possible from skin breaks and bruises through which infection

can take place.

It is important to reduce the source of contamination. There

is a definite correlation between the number of rotting fruit and

the number of spores present on the fruit, in the air, and on

equipment. Sanitation of field boxes and packinghouses is very

important. Where possible, fruit arriving in a packinghouse

should be unloaded and cleaned in a separate area to reduce

contamination in the processing, packing, and storage areas.

Field and storage boxes are often treated with formaldehyde,

other disinfecting solutions, or live steam. Packinghouses are

fumigated with chlorine gas, or all surfaces are thoroughly

covered with atomized pine-oil emulsions, formaldehyde, or other

disinfectants.

Preharvest sprays of fruit in the orchard have not been

effective in reducing postharvest decay, probably because the

vast majority of rind injuries occur during harvesting or packinghouse handling.

Fruit, especially lemons, should be cleaned and then treated

in a hot (110° to 120° F.) antiseptic solution as soon as practical

after arrival at the packinghouse. Heat or fungicides kill spores
12 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

on the fruit and eradicate many of the infections that are just

getting started in rind injuries received during picking. The

rind injuries may absorb or take up enough fungicide to inhibit

infection by fungus spores picked up during later processing and

packing. To avoid liberating oil from the rind and causing greenspotting and decay, it is often necessary to hold fruit at the

packinghouse for 24 to 72 hours before v^rashing or to reduce

the temperature of the wash solution. Holding fruit too long

allov^s the fungi in wounds to grow more deeply into the rind,

where fungicides or heat will not eradicate them. Too early

treatment of turgid or sensitive fruit may release oil or damage

the rind, creating sites for future infections.

Fungicidal wash treatments now used commercially include

soap solutions, borax, or mixtures of borax and boric acid or

borax and pentabor, soda ash, thiabendazole (TBZ), and sodium

O'-phenylphenate (SOPP). Sodium o-phenylphenate has also been

used with detergents as a foam or lather brushed onto the fruit.

Fungicide wash treatments are more effective when used hot.

Temperatures of 90° to 120° F. are used, depending on the susceptibility to injury of different lots or varieties of fruit

Detection of early infections, in the pinhole or blister rot

stages, is greatly aided by using black (ultraviolet) lamps, under

which the lesions are easily visible.

During storage and transport, other supplementary aids or

precautions help reduce fruit decay. Volatile, in-package fungistats such as biphenyl, or ammonia-emitting chemicals, or nitrogen trichloride-forming chemicals impregnated in paper sheets,

will retard fungus growth and help prevent spread of decay.

Nitrogen trichloride gas has been used to fumigate fruit in

storage or in closed refrigerator cars after loading. Biphenylimpregnated kraft paper sheets inserted in the citrus cartons

during packing are commonly used and, in combination with

proper refrigeration, effectively retard development and spore

production of green-mold and blue-mold rots.

Refrigeration of fruit at 40° to 45° F. almost completely retards growth of most decay fungi. Pénicillium green and blue

molds, however, will grow very slowly below 40°. Holding fruit

under proper refrigerated conditions is very necessary in delaying mold development. When fruit are returned to warm

conditions, molds resume growth, and infected fruit will decay.

(See 20, 21, 22, 23, 86, US, 76, 78, 95, 97, 98, 99, 108, 113, 115,

120, 182, 136, U7, 150, 151, 156, 161, 17Jf, 201, 202, 206, 207,

208, 209, 228, 229, 230, 2^6, 2i7, 21^8, 250, 263, 282, 28Jf.)
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 13

Botrytis^ or Gray-Mold, Rot

Botrytis cinérea Pers. ex Fr.

Occurrence, symptoms, and effects

Botrytis rot caused by the fungus Botrytis cinérea has been

reported from most of the citrus regions of the world. It is

primarily a storage, transit, and market disease, but it may

occur to some extent in orchards. It is most common on lemons,

then oranges, but it may decay other kinds of citrus fruit.

The early stage of the decay may closely resemble sclerotinia

or cottony rot, but distinguishing characteristics soon become

evident. In the early stages of botrytis rot the decaying tissues

are firm, but later they become leathery and pliable. The affected

surface of a lemon becomes drab or cinnamon brown and later

may turn buff or dark brown, darker than cottony rot. The color

of the affected surface of an orange is medium to dark yellowish»

brown. The mycelium that develops in moist air is white but

includes a mass of gray spores (pi. 2, (7). The gray, granular»

appearing spore tufts are characteristic. The rind, core, and

membranes are invaded by the fungus faster than the pulp is.

Causal factors

The fungus causing botrytis rot lives on decaying leaves, twigs,

fruit, and organic matter in the soil. Spores are spread by rain,

wind, and insects. Decay generally starts at the button, on the

cut stem, or at injuries. Also, the fungus can grow from bits

of organic matter and penetrate through uninjured rind. Citrus

fruits stored at 60° to 70° F. may become entirely rotted in

2 weeks or less. B. cinérea can grow at very low temperatures,

and even at 32° F., decay develops slowly.

Control

Control measures are similar to those for brown rot. Briefly,

they are (1) avoid leaving picking boxes for very long on the

ground in moist weather, (2) prevent injuries to fruit, (3)

keep fruit from contact with organic matter and trash, (4)

wash the fruit at 115° to 120° F., (5) avoid excessive humidity

in storage rooms, (6) inspect fruit in long storage frequently

to remove decayed fruit, and (7) refrigerate fruit to prevent

rapid decay.

(See 26, 76, 186, 137, 208, 209, 281.)
14 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

Brown Rot

Phytophthora citrophthora (R. E. Sm. et E. H. Sm.)

Leonian^ P. parasítica Dast., P. syringae (Kleb,) Kleb.,

F. hïbernalis Carne, and other Phytophthora species

Occurrence, syniploms, and effects

Brown rot occurs on citrus fruit in orchards, packinghouses,

storage, and transit. The disease, caused by any of several phytophthora species, is found in all principal citrus-growing areas

of the world. The rot attacks all citrus varieties but is most

important on lemons. Mature fruit is attacked more frequently

than green fruit.

Decay produced by brown rot is remarkably firm and leathery.

Affected areas do not soften rapidly, despite their soft appearance.

The first symptom of the disease^is a slight olive-drab or brownishtan rind discoloration. Later this rind discoloration may appear

dark greenish-brown (pi. 2, D and E). The aiïected areas remain ñush with the level of the surrounding unaffected rind.

The juice of lemon is too acid for this fungus, so in lemons the

mold usually grows only in the rind, core, and tissues between

the segments. Usually there is no evidence of mold on the fruit

surface, but under very humid conditions a delicate, white fungus

growth will appear. Brown rot can infect other fruit by contact,

and thus spread in stored or packed fruit. The disease can be

identified by a rather penetrating, aromatic, rancid, or fermented

odor. Some other forms of decay leave the fruit somewhat firm,

but only the phytophthora brown rots have this distinctive odor.

In later stages, after secondary decay organisms have invaded

fruit affected with brown rot, decomposition is rapid and the

tissues are soft.

Causai factors

The phytophthora fungi causing brown rot are common in

soil. Most infections occur within 3 to 4 feet of the ground, as

a result of the splashing of the motile swimming spores onto

the lower leaves and fruit during rains. Winds during or immediately after rains or moist periods can carry spores high

into the trees and cause infections 20 or 30 feet from the ground.

For the fungus to cause infection, the fruit must be wet for a

relatively long and uninterrupted period. Evaporation of moisture
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 15

from fruit before the fungus spores germinate and penetrate the

rind will stop the infection process. Rain is not the only cause

for moisture on fruit, and any moisture which remains for long

periods provides conditions ideal for infection.

In the orchard, the infected fruit rots and eventually drops

from the tree. If fruit is harvested during the 3- to lO-day period

between infection and appearance of rot symptoms, infected

fruit are carried into the packinghouse and processed. During

storage or transit the disease develops and can be spread from

infected fruit to adjacent healthy fruit.

Control measures

Control of brown rot should be carried out in the orchard,

as well as in the packinghouse. Ideally this disease ought to be

prevented in the orchard. This can be partly achieved by applying fungicidal sprays before or just after rainy or moist periods.

Pruning and cultural practices should be used to reduce chances

that spores from the soil will splash onto fruit. Picked fruit

should not be placed on the soil, nor should boxes of fruit be left

on the soil during rainy or foggy periods.

In California, the immersion of fruit for 2 to 4 minutes in

wash solutions at 115^ to 120° F. has been effective in eradicating

infections, provided the period from infection to treatment is

short and the fungus is still confined to the external layers of

the fruit rind where heat will penetrate rapidly. The rate of

growth of the fungus into the fruit depends chiefly on fruit

temperature, but also on fruit maturity. Picked fruit should be

delivered to the packinghouse promptly and given the hot-water

treatment as soon as possible. However, turgid fruit picked in

cool or humid weather can be severely injured if immersed immediately in hot wash solutions. Heat-injured fruit is susceptible

to decay by other rot organisms. A strong soap added to the

wash solution helps emulsify rind oil and reduce injury. Lemons

are usually more sensitive to heat injury than are oranges. If

possible, lemons should be held from 1 to 4 days at the packinghouse until wilted sufficiently to tolerate the heat treatment. If

holding is not practical, then a lower temperature should be

used for the wash solution. However, the longer the infected

fruit is held before treatment, the deeper the fungus penetrates

into the fruit. Cooler wash solutions are not as effective in killing the fungus as are the 115° to 120° treatments. Hot water

alone is as effective for brown-rot control as are hot fungicidal

solutions, since only heat can penetrate the rind and reach the
16 AGRICULTURE HANDBOOK 398, U.S. DEPT, OP AGRICULTURE

fungus. Cold fungicidal solutions cannot eradicate established

infections, but they will kill fungus spores accumulating in the

wash solution and thereby prevent them from infecting healthy

fruit. Soda ash and sodium o-phenylphenate (SOPP) are fungicides often used in the hot wash solutions to control blue and

green molds and other decay fungi.

Volatile chemicals often used during transit have not proved

effective against the brown-rot fungi. Fruit should be stored and

shipped refrigerated (below 50° F.), since most brown-rot phytophthora species grow slowly or not at all at cool temperatures.

(See 58, n, 76, 132,133, 13U, 135, 136, 139, HO, lU, U2, lU,

1Í5, llf?, 182, 183, 201, 208, 209, 267.)

Chewmg-Insect Injury

When citrus fruits are young, they are sometimes attacked

by grasshoppers, katydids, and other voracious chewing insects,

which eat away the rind over areas of varying size on any part

of the fruit. Some of the injuries are probably so severe that

they cause the fruit to drop. Others heal over, producing a

roughly circular or oblong scar, which on mature fruit may be

an inch or so in diameter. The edges are sharply sunken below

the level of the rest of the rind (pi. 5, A). These scars are smooth

and have the same color as the rest of the fruit, but they are

devoid of the oil glands characteristic of the rind. All citrus

fruits may be affected, but the injury is more common on oranges

and grapefruit than on other fruits. Scars on the mature fruits

do not act as avenues for decay fungi.

This type of injury is best prevented by cultural practices

and spraying in the orchard to control the insects that cause

the damage.

(See^^, 201, 208.)

Chilling Injury

Chilling may injure citrus fruits stored at low temperatures

but above the actual freezing point of the fruit. Lemons, limes,

and grapefruit are most susceptible to injury caused by chilling.

Oranges are least apt to be damaged. Tangerines, tangelos, and

other mandarin-type fruits are intermediate.

Symptoms of chilling injury are quite varied. They may be

external in the form of pitting, brown staining, oil-gland darkening, diffuse rind breakdown (scald), or albedo browning.

Watery breakdown involves the whole fruit, while membranous
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 17

stain of lemons affects only the segment walls and core. The susceptibility to chilling injury is very unpredictable. Considerable

variation in type and severity of injury occurs from year to year

with fruit from the same orchard. Occasionally more than one

type of chilling injury may develop on the same fruit. These

symptoms may develop after 2 weeks or longer at unfavorable

temperatures.

Albedo Browning

Albedo browning, which affects only lemons, is a discoloration

of the white, spongy inner tissues of the rind. The disease may

show externally as a slight, pebbly, brown-to-gray darkening of

the rind where the discolored albedo shows through the surface

layer. It tends to develop on fruit in storage at low temperatures

(32'' F.) and with poor ventilation, especially fruit that was

harvested at an immature or dark-green stage (pi. 7, H),

Brown Staining

Brown staining may affect most citrus fruits, although grapefruit and mandarins are most susceptible. It is a diffuse, irregular, tan-to-brown superficial discoloration of the peel (pi.

8, B). It may involve a small area or the whole surface of the

fruit. It is usually observed on fruit stored at 32° to 34° F.

When the fruit is removed to room temperature, the discoloration

usually fades or disappears completely after several days. In

severe cases, pitting or collapse of surface tissues may accompany the discoloration (pi. 7, F).

Membranous Stain

Membranous stain, or membranosis of lemons, is characterized

by a browning or darkening of the membranes or carpellary

walls between the segments. The core tissues and the inner

tissues of the rind also may be affected. The disorder can be

detected only when the lemons are cut. It can be seen best when

the segments are pulled apart for a longitudinal view (pi. 8, C).

This disorder is more prevalent in fruit picked in cool, damp

weather. It is extremely responsive to storage temperature.

Lemons held at 40° F. become seriously affected, whereas those

held at either 32° or 60° seldom develop sufficient stain to be

seriously damaged.
18 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

Oil-Gland Darkening

Darkening of the oil glands has been observed in grapefruit

and tangelos subjected to chilling temperatures (pi. 8, A). This

prominent discoloration of the oil glands gives a polka-dot appearance to all or part of the surface of the fruit. In severe

cases or with fruit left for longer periods in storage, the space

between the oil glands also becomes discolored and may collapse,

giving a scalded or heat-damaged appearance to the rind. Internally, severely affected fruit may become soft and disorganized

as with watery breakdown.

Pitting

(See Storage Pitting, page 32.)

Watery Breakdown

Citrus fruits affected with watery breakdown are soft and

spongy and have a soaked appearance resembling that of fruit

that has been frozen. The flesh as well as the rind may be

softened. Within the affected fruit, the carpels are loosely attached

to the inner part of the rind. When a section of the rind is pressed,

a watery substance oozes freely from the albedo.

Watery breakdown is a low-temperature disease found most

often in fruit stored at temperatures below 40° F. However, even

at 32° it does not develop until after several weeks of storage.

Affected fruits have a disagreeable odor of fermentation that is

particularly noticeable when they warm up after removal from

storage. Watery breakdown may occur without other symptoms

of chilling, or it may follow such symptoms as brown staining

and oil-gland browning. The water-logged tissues usually do not

contain decay organisms in the initial stages, but they may later

become infected with Pénicillium, Geotrichum, and other fungi.

Control of Chilling Injuries

Chilling injuries obviously can be prevented largely by using

temperatures at which injury does not occur. However, in actual

practice it is not this simple, since decay increases at higher

storage temperatures. A compromise must be made, with all

factors considered, in determining the best storage temperature.

The same variety of citrus grown under different climatic conditions may well have different storage temperature requirements.

Generally, California and Arizona fruit are more susceptible
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 19

to low-temperature disorders than those of the same variety

grown in Florida and Texas.

There appears to be no shortcut for successful long storage of

citrus. Fruit must be harvested at proper maturity, handled

carefully, given proper fungicidal and wax treatments, and stored

promptly at recommended temperatures (table 1) and 87 to 92

percent relative humidity to prevent drying out.

(See 33, 76, 136, 157, 208, 273,)

TABLE 1.—Recommendations for storage of citrus fruits

[Relative humidity 87 to 92 percent]

Variety

Production Storage Length of

area temperature storage period

0 p Weeks

Florida 38-40 2-4

Florida 38-40 4

Florida 38-40 4

Florida 32-34 6-8

Florida 32-34 8-12

Texas 32-34 8-12

California 40-44 4-6

California 40-44 4-6

Florida 50 4-6

Texas 50 4-6

California 58-60 4-6

Arizona 58-60 4-6

Florida 48-50 6-8

California 58-60 12-24

Dancy tangerines

Tangelos

Temple oranges

Murcott Honey oranges

Valencia oranges

Do

Do

Navel oranges

Grapefruit

Do

Do

Do

Limes ,

Lemons

Citrus Rust Mite Russeting

Phyllocoptruta oleivora (Ashmead)

Occurrence, symptoms^ and effects

The citrus rust mite and the russeting it causes occur in the

Gulf States, the West Indies, and to a much lesser extent in

California and Arizona. Although the mite may attack all commercial varieties of citrus, most of the damage is done on grapefruit and oranges.

Rust mites injure both leaves and fruit; but the injury to the

fruit is most important. The injuries differ with the variety of

fruit and the time and intensity of the mite infestation. Early-
20 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

season injury to grapefruit, lemons, and limes appears as silvering of the peel and, if severe, is known as '^sharkskin." Earlyseason injury to oranges causes a brov^^n scarring and cracking

of all or part of the fruit surface (pL 5, D). Severe early injury

of citrus fruits may result in small-sized fruits. Early-infested

fruits will not take a sheen when waxed and polished.

Injury during late summer and fall is a smooth brown staining of the fruit, which permits a high polish (pi. 5, E), On

grapefruit it is called "bronzing.'' In some markets bronzed

fruits bring premium prices because they are thought to be

sweeter than uninjured fruit. Injured oranges may show a

smooth purplish staining, otherwise similar to grapefruit injury.

Summer injury may be somewhat intermediate between the early

and late injury described above. Some fruits develop a streaking

or a tearstain effect down the sides. Tearstain caused by rust

mite is smooth and diffuse in contrast to melanose tearstain; the

latter is a series of raised spots that are darker in color and

have a sandpapery feel.

Russeted fruit is less attractive in appearance than bright

fruit. The injury to the skin, whether early or late, does not

render the fruit more liable to decay than unblemished fruit,

but does cause it to lose water and shrivel rather rapidly under

ordinary storage conditions. For this reason, russeted fruit should

not be stored longer than is required for orderly marketing.

Causal factors

The citrus rust mite (P. oleivora ( Ashmead) ) is a lightyellow, wedge-shaped arachnid about 1/200-inch long. It injures

fruit by sucking the juice from the skin. Mites are not likely

to be found on fruit that has gone through washing and polishing in the packinghouse, but the evidence of their prior presence,

of course, remains. Fungi have been reported to be associated

with rust mites in causing the russet symptoms by secondary

invasion; however, this has not been fully substantiated. Other

mites have been reported to cause injury to fruit, but they are

not generally associated with the russeting described above.

Control measures

The most effective means of preventing russeting is to control

the rust mite population by dusting or spraying with recommended miticides.

(See 4, SI, 62, 76, 80, 88, 186, U7, 201, 208, 279.)
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 21

Cottony Rot

Sclerotinia sclerotiorum (Lib.) dBy.

Cottony rot, caused by the fungus Sclerotinia sclerotiorum, is

widely distributed in many of the citrus-growing regions of the

world. It is found chiefly in lemons, but it may affect other

citrus fruits.

Affected fruit softens slowly, but the skin is at ñrst leathery

and pliable. In a dry atmosphere, the color of decayed areas on

mature fruit becomes yellowish-brown or greenish-brown. In a

moist atmosphere, the fruit is rapidly covered with a white,

cottony growth of mycelium that is the outstanding distinguishing characteristic of this decay (pi. 2, F and G). Black, irregularly shaped sclerotial bodies %6 to % inch long later develop

in the fungus mat.

Cottony rot is a rapidly spreading contact decay that may attack either green or mature fruit. Although it is not common,

it may cause heavy losses in the packinghouse or in storage.

Moderate temperatures, high humidity, and stagnant air favor

its development. However, the causal fungus is able to grow to

some extent even at temperatures close to freezing and hence

may cause damage in transit and storage at the temperatures

ordinarily provided. Careful handling, packinghouse and ñeld

sanitation, and washing the fruit in hot water as for brown rot,

are recommended preventives.

(See 75, 76, 186, 208.)

Creasing

Creasing is a condition found in mature and overripe oranges

and mandarin-type citrus fruits. It is characterized by narrow

sunken furrows or irregular grooves in the rind, usually less

than 14 inch wide and from 1/2 to 2 inches long (pi. 4, G). The

sunken creases are due to weakness or uneven thickness of the

albedo, the underlying white spongy part of the rind. If a thin

paring is made, or if the peel is completely removed, it can be

seen that the albedo is thin or there is a void in the albedo

beneath the creased area (pi. 4, H), These creases may extend

both longitudinally and crosswise and in severe cases may run

together to produce large areas of uneven rind. In small narrow

creases, the color of the sunken skin is normal, but in larger

ones it may be yellowish green to gray. When fruit is subjected

to hot solutions, such as used in the **color-add*' treatment, creases
22 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

become more apparent, the sunken rind often becoming watersoaked or split.

Mild creasing of California oranges is not considered a serious

defect because the rind is pliable, and few of the fruits split

open from pressure during packing and shipping. Florida fruit,

however, has a thinner and more brittle rind, so that creased

areas split more easily. The cause of creasing is not known, but

it may be associated with potash and phosphorus nutrition of the

trees.

Creasing does not increase after harvest, but creases in fruit

that has been subjected to hot solutions or pressure due to tight

packing and high stacking of containers may split during transit

and subsequent handling and open the way for blue-mold and

green-mold rots.

(See 136, 201, 208.)

Endoxerosis (Internal Decline)

Occurrence, syiiiptoiii§, and eflfects

The term *'endoxerosis,'' meaning "internal drying/* is used

to describe a physiological abnormality of lemons. Several names,

especially "internal decline," but also "tip deterioration," "yellow

tip," "pink tip," "dry tip," and '%lossom-end decline," have been

used by growers, packers, and shippers for this condition.

Endoxerosis has been recognized by lemon growers in California for at least 70 or 80 years. It is more prevalent in the

drier, warmer interior valleys than in the more humid, cooler

districts near the coast. All varieties are susceptible. In California it usually appears first about May or June, develops to its

maximum in the dry summer, and extends into early autumn.

It has been reported from Sicily, Australia, and Israel also, but

the symptoms described differ somewhat from those in California,

probably due to differences in varieties and environment.

The disorder is characterized by the destruction of internal

tissues, especially at the stylar end of the lemon. Cells collapse

and may disappear entirely, leaving cavities in the peel at the

stylar end. Affected tissues become pinkish or brownish in color.

As the disease progresses, an exúdate or gummy substance, at

first colorless but later pinkish or straw-brown in color, is deposited in or next to the peel near the cavities. The gum formation starts in the stylar end, but as the disorder becomes more

severe it advances through the core into the basal end and even

into the buttons. Such advanced cases are not often seen on the
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 23

market, since severely affected fruit has a tendency to float in

water, with the stylar end up. This, along with external symptoms, allows most seriously endoxerotic fruit to be culled out

at the packinghouse.

External symptoms of this disease are vague and difficult to

detect. On green fruit the disease may be indicated by a loss of

luster or the development of a yellow color at the stylar end

while the rest of the surface is still a normal green. On either

silver or yellow fruit, it is difficult to detect endoxerosis by

external symptoms, especially in mild cases. Sometimes there is

a more intense color of the rind at the stylar end, and a collapse

of the tissues at the base of the nipple may cause it to bend over.

Causal factors

The principal cause of this disorder is believed to be related

to water conditions within the tree and the fruit, which in turn

are influenced by the moisture supply, temperature of air and

soil, and growth conditions for the tree. Decay organisms are

not responsible for endoxerosis, but endoxerosis is frequently confused with alternarla rot, which sometimes accompanies or follows it, Endoxerosis develops only while lemons are on the tree.

It will neither start nor progress in fruit once it is harvested.

Control measures

In the orchard endoxerosis can be partly prevented by keeping

water conditions as favorable as possible for tree health. It also

helps if lemons are picked while green and are not allowed to

become too old or tree ripe. In the packinghouse, affected fruits

are usually recognized in the wash tank or on the inspection

line and removed.

(See 18, S3, 76, 136, 208.)

Exanthema (Ammonialion)

Occurrence, symptoms^ and efifects

Exanthema is a nonparasitic, nutritional disease of the fruit,

leaves, and twigs of all commercial citrus. It occurs in practically

all the citrus-growing regions of the world. In the United States

it is more common in Florida, especially on oranges and grapefruit. It is less prevalent now than in past years, due to routine

application of minor elements, including copper. It is seldom

seen in commercially packed fruit.
24 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

The distinguishing characteristics of the disease are darkbrown, glossy spots on the rind of the fruit (pi. 4, F), which

may be of various sizes and shapes. Gum pockets may sometimes

be found in the albedo of thickskinned fruit when no symptoms

appear on the surface. The surface spots or scars may be pimplelike and reddish-brown, coalescing to form large roughened areas

on the fruit, or they may be smooth and flat, or concave and

rough. In many instances the rind is hard and stiff. This causes

cracks as the fruit grows or when the affected areas dry out

more rapidly after harvest than the sound areas. These cracked

and split fruit are likely to decay after secondary invasion by

Pénicillium digitatum or stem-end rot fungi. Gum may also form

in the angles of the segments of the fruit along the central axis

or core. The pimple stage of exanthema on the fruit is sometimes

mistaken for melanose. The two can be distinguished by the fact

that exanthema originates in tissues beneath the epidermis and

thus seems to come up through the epidermis, while melanose

is on the surface of the rind.

Causal factors

Exanthema is caused by a deficiency of copper. The disease

is most common on trees with poor drainage, where the soil is

underlain by hardpan, or where the moisture supply is irregular.

The trouble may be aggravated or become more pronounced

just after high nitrogen and phosphorus fertilization. These

factors, however, are not directly responsible for exanthema and

are important only when copper is deficient.

Control measures

Exanthema is effectively controlled by orchard application of

copper sprays for the control of scab or melanose, by soil application of copper sulfate, or by supplemental nutritional minor-element sprays. Since copper may also cause toxicity to citrus trees,

it should be applied in only trace amounts.

(See 4 28, 76, ISO, 136, U5, 1Í7, 201, 206, 208, 2U^)

Freeze Damage

Citrus fruits will freeze and subsequently show freeze damage

at temperatures ranging from 25° to 30° F. and averaging about

27.5° F. In general, tangerines, lemons, and limes freeze at the

higher limits of this range, oranges are at the lower end, and
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 25

grapefruit and hybrid fruits are intermediate. However, considerable variation occurs between varieties and sources within

varieties, so that all citrus fruits are likely to show freezing

injury when subjected to temperatures below 30° for sufficient

time. The flesh of the fruit freezes at a slightly higher temperature than the rind of the same fruit.

Postharvest Freezing

Freezing injury in transit is more likely to occur in the fruit

next to the side walls and along the floor of the car or van, or

near the air delivery, than in fruit in the body of the load.

Freezing damage in oranges is best identified by cutting off both

ends of the fruit, then cutting through the rind of the central

part remaining, and pulling the segments apart. If the fruit has

been frozen, the membrane between the segments will look soaked

and usually will contain a number of white specks, which are

hesperidin crystals (naringin in grapefruit) resulting from the

freezing (pi. 7, A). In tangerines, the hesperidin crystals occur

in the pulp as well as on the segment walls and are, therefore,

evident in cross section. If the freezing has been severe, the rind

may show effects ranging from a typical brown stain to gray

discolored areas of varying size. The affected rind tissues may

or may not be sunken. When severely frozen they usually become

soft and mushy and are underlain by mushy pulp. Lemons and

grapefruit show damage in cross section much more plainly than

oranges, although it is desirable at times to pull grapefruit

sections apart for viewing as recommended for oranges. If lemons

have been seriously damaged, the pulp becomes mushy immediately after thawing.

Grapefruit shows, in addition to the symptoms described above,

a milky appearance of the pulp, which is in marked contrast to

the very light amber color and almost transparent look of the

unfrozen pulp. The contrast is especially noticeable in fruits

that have been frozen on only one side.

A positive diagnosis of fruit frozen in transit or storage

must depend on a consideration of the history of the fruit and

the conditions under which the injury is found.

Freezing on the Tree

Citrus fruit frozen on the tree shows a number of the symptoms described under postharvest freezing, if examined soon

after the freezing occurs. After a few days, however, additional
26 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

symptoms appear. First and most characteristic among these is

a buckling of the partition walls at the stem end of the fruit,

with or without drying of the pulp (pi. 7, B and C). Small pits

or pitted areas may also develop in the rind on any part of the

fruit. In fruit on the market, picked several days after it had

been frozen on the tree, the injury is shown by woodiness of the

pulp or by open spaces between the segments after the collapse

and drying out of some of the juice sacs. Cavities usually appear

in the orange pulp before open spaces develop between the segment walls. Later, when the pulp has dried out considerably, small

open spaces appear between these segment walls. Sometimes only

one or two segments will be dried out, and all or only a part of the

segment may be affected. Where only one or two segments are

affected, considerable time is required for them to dry an inch

or more.

There are, of course, all degrees of dryness, from very slight

to total. In the practical handling of citrus fruit, three degrees

are recognized: (1) Slightly open, in which the cut surface shows

a slight open space between the segment walls and the juice sacs,

but the surface of the pulp appears juicy; (2) distinctly open,

in which the cut surface shows large open spaces, but the pulp

still appears juicy; and (3) dry, in which the cut surface shows

no large open spaces, but the fruit seems to have dried out evenly

all through, and the color of the pulp shows it to be almost devoid

of juice, or when the fruit has dried out and some of the segments have more or less collapsed.

Drying in oranges usually progresses from the stem end. In

grapefruit it may proceed from, either or both ends, or it may

begin around the outside of the pulp. The center of the fruit is

not dried except in extreme cases. If an orange that has been

frozen is examined a few days after it thaws, it will usually

show the hesperidin crystals already mentioned on the membrane or rag that separates the segments of the pulp. Sometimes

the crystals can be seen within a few hours after the freezing.

Several weeks after freezing, the crystals may not be so numerous or conspicuous, probably because the more severely frozen

fruit falls soon after the freeze. Fruit that has remained on the

tree for several weeks after freezing has a rind that is thicker

than normal, especially over the damaged part of the fruit.

Dryness from freezing differs from dryness of granulation

because the juice sacs are collapsed after they have been emptied

by disappearance of the juice. In granulation the juice sacs do

not collapse but become filled with gelatinous or solid matter.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 27

Fruit frozen on the tree dries out as described above and is

consequently lighter in weight. Flotation devices at the packinghouse can be used to separate severely or moderately dried fruit

from fruit that is normal or only slightly dried. The internal

quality of an orange is still considered U.S. No. 1 if drying

does not exceed a depth of l^ inch into the flesh from the stem

end.

{See 157, 208, 277.)

Fusarium Brown Rot

Fusarium spp.

Fusarium brown rot is a minor decay of both oranges and

lemons. It has been reported from most citrus-producing regions

of the world. Since this decay develops slowly, it is more important on fruit that is held in storage for long periods than

on fruit held for short periods.

Fusarium rot is similar, in most cases, to the rot produced by

either Colletotrichum or Alternaria, The decay varies from a semipliable form somewhat resembling the later stages of anthracnose

rot to almost a soft rot. It may become nearly as soft as the alternaria rot of lemons. Infection usually starts at the stem end,

occasionally at the stylar end, and very rarely elsewhere on the

mature fruit surface, unless there are wounds. A soft brown

spot is formed, and under humid conditions a white surface mycelium appears. The lesions vary somewhat but are generally

dark brown in color, leathery, and sunken (pi. 2, H), Occasionally the center of the lesion becomes watersoaked and softer

than the surrounding area. The fungus grows through the center

of the fruit, causing considerable internal breakdown and a generalized, reddish-brown discoloration of the center, which is

almost the typical symptom. This fungus is often mixed with

other fungi.

Fusarium rot can be caused by several species of Fusarium.

Low vitality of fruit and any tendency to slight separation of

tissue at the navel end of oranges contribute to its development.

This decay as a rule is not important enough commercially to

require control measures. Storage and shipping at 40"^ F. suppresses development.

(See 13, US, 60, 76, 83, 121, 136, 209,)
28 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

Granulation

Occurrence, symptoms, and eflfects

Granulation is a physiological disorder. It consists of dryness

of juice sacs or vesicles of citrus fruits that have not been exposed

to freezing temperatures. Other names include ''dry end/' "crystallization,*' ''Koa Sarn," and '*corkiness." A technical name,

*'sclerocystosis/' has been proposed.

Granulation has been reported from all citrus areas in the

United States. In California, granulation is primarily a problem

of late-season (July to October) Valencia oranges, but earlyor midseason fruit also may show it. It is more common in fruit

from coastal areas and on frequently watered trees than in fruit

from the interior. In Florida, navel and Valencia oranges and

mandarin hybrids are most likely to show granulation late in their

shipping season.

Affected juice sacs, particularly at the stem end, become comparatively hard and firm by thickening and stiffening of their

walls, assume a clear-white or grayish color, and become somewhat enlarged. The condition is not generally evident until the

fruit is mature. The name granulation is appropriate because the

juice sacs are hard and are easily separated from each other, and

because the affected pulp assumes a texture of grains or granules.

Finally, a dry, woody, solid condition results. Granulation usually

starts in the stem end of the fruit, but in some varieties and in

certain areas the condition can appear throughout the pulp. Even

in fruits affected only at the stem end, the granulation as seen in

cross section affects all of the segments and not merely small

spots in two or three segments, as so often happens in freezing

injury (pi. 6, H).

In tree-frozen fruit the juice sacs collapse, wither, and separate from each other and from the segment walls. The fruit is

soft and light in weight. In granulated fruit the juice sacs do

not separate from each other or from the segment walls; they

remain turgid, the juice being replaced by solid matter that is

yellow-to-grayish white. Such fruit feels firm but is light in

weight.

Granulation is almost impossible to detect by any external

markings. The only reliable diagnosis is made after cutting the

fruit. Granulation develops while fruit is on the tree and does not

progress materially after harvesting.
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 29

Cause and control

Granulation is a growth phenomenon. Rapidly growing and

larger fruits that have received nitrogen applications have a

greater tendency to granulate than do slower growing, smaller

fruits. Some rootstocks, especially rough lemon, tend to induce

it more than others. Early picking when possible may avoid

some losses from granulation. Preharvest use of 2,4-D delays

or reduces severity but does not prevent the disorder.

(See 76, 110, 186, 15i, 208,)

Melanose

Phomopsis citri Fawc.^

Melanose occurs in all citrus-growing regions of the United

States and elsewhere. It is most prevalent in areas of high

humidity and summer rainfall, such as Florida and other Gulf

States. It is exclusively a field disease. It lowers the grade of the

fruit on the market because it greatly affects the appearance.

Leaves, young twigs, and fruits of all Citrus plants are affected.

Of the commercial citrus fruits, grapefruit is the most susceptible. On the fruit, the disease can be recognized as small, brown,

raised spots or pustules, produced when the causal fungus attacks

and kills a few epidermal cells of the rind during the early

development of the fruit. In these spots the fungus usually dies

long before the fruit matures. The individual spots are usually

about the size of a pinhead (pi. 4, A), although they may coalesce

to form rather large scablike patches known as **mudcake" melanose (pi. 4, S). It may appear as a tearstain where water from

rain or dew previously has run down the side of the fruit carrying

spores with it (pi. 4, C). Melanose may be distinguished from

rust-mite injury by its sandpapery feel and definite pustules

rather than the smooth diffuse appearance of the rust-mite injury.

Melanose does not spread in storage or transit.

Control measures

In an average season in Florida, the disease is readily controlled by a single copper spray applied 1 to 3 weeks after petal

^ The perfect stage, Diaporthe citri Wolf. P. citri also causes a stem-end

rot.
30 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

fall, since only the very young fruit are susceptible. The removal

of dead wood and twigs, the source of the infective spores, is also

beneficial

(See Jf, 10, 76, 136, 1^7, 201, 205, 208, 226, 279, 285, 286, 288,)

Modified Atmosphere Injury

Controlled levels of oxygen and carbon dioxide in storage (CA

storage) may be used to supplement refrigeration to maintain

the quality of fruits and vegetables for extended periods. Nitrogen also may be used during transit in rail cars and piggyback

containers for the same reason. However, improper modification

of the atmosphere often leads to injury and off-ñavors in citrus

fruits (pi. 6, F). Poor air ventilation during long domestic shipments with delayed unloadings or in export shipments may also

cause similar injuries.

Oranges seem to be particularly susceptible to injury from low

oxygen or a combination of low oxygen and high carbon dioxide.

A type of scald may be produced on Florida Valencia oranges

stored in 5 percent oxygen. This injury appears as large, darkbrown, abruptly sunken areas, frequently covering more than

half the fruit and producing an acorn-like appearance (pi. 6, E),

If the fruit is held for extended periods in oxygen levels below

5 percent and carbon dioxide levels of 5 percent or higher, the

rind will develop a light-brown pebbly appearance around the

stem end. An internal watery breakdown may develop, accompanied by a high level of ethyl alcohol and a fermented odor and

flavor. Normal-appearing fruit from the same lot will be offflavored.

Control measures

Only atmospheres recommended for a specific variety, from

a specific growing area, should be used, and for the recommended

length of time. Avoid mixing varieties or kinds of citrus fruit

in the same CA storage or using an atmosphere recommended

for other fruits or vegetables. The atmosphere should be carefully monitored during the storage or transit.

In air storage or long transit of citrus fruits, adequate ventilation must be maintained to prevent depletion of oxygen or

buildup of carbon dioxide. Vents should be periodically opened

and the water drains kept clear to allow for air exchange.

(See 4^, i7, 2i6.)
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 31

Oil Spotting (Oleocellosis)

Rind oil spotting is found on citrus fruit from all producing

regions. It is worse and probably most commonly seen on lemons

and limes. It is also found on other citrus fruits, especially Marrs

Early and navel oranges harvested early in the fall before they

have lost their green color (pi. 9, A). The most common symptom

is irregularly shaped yellow, green, or brown spots in which the

oil glands of the skin stand out prominently because of slight

sinking of the tissues between them. The yellow spots develop on

fully colored mature fruit, and the green spots develop on fruit

that was green in color when picked. Brown spots are either a

later or older stage of spots that were originally green or of

spots that were more severely injured. Spots seen on fruit on the

market are usually not more than one-half inch across, but some

in orchards and packinghouses are so large that they cover the

greater part of the fruit surface. In either the green or the brown

stage they become more evident after the fruit has been degreened.

Oil spotting is a form of bruising injury. It is particularly

likely to occur on immature citrus fruit if it is handled while

wet or turgid. The immediate cause is liberation of oil from

ruptured oil glands by mechanical injury. Pressure incident to

the picking and handling of green-colored fruit is particularly

likely to cause the green spots, and bruises incident to packing

degreened fruit cause yellow or brown spots. The severity of the

injury depends on the quantity of oil released. Field freezing or

insect punctures may also liberate oil and cause spotting (pi.

9, B). Fruits with raised, prominent oil vesicles are more likely

to show oil spotting than those with less prominent ones.

Control

Oleocellosis is controlled by avoiding the conditions that contribute to the escape of oil from rind. Avoid picking fruit when

it is wet with rain or dew or during periods of high humidity

(morning hours, or cloudy days). Avoid rough handling that

might liberate the oil, especially during the early part of the

season. A pressure tester to determine the rind oil rupture pressure (RORP) can be used to determine when the fruit has lost

sufficient turgidity to be handled without injury.

(See JfO, 72, 76, 127, 136, US, 186, 201, 208, 26i.)
32 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

Pitting

Pitting occurs on all types of citrus fruits but is more prevalent

on grapefruit and oranges. It consists of abruptly sunken spots

in the rind. It is a physiological breakdown of the rind on the

shoulder or cheek of the fruit, in contrast to "aging/' a breakdown of the rind at the stem end. The spots are not discolored

at first, but later they may become slightly pink-to-tan on grapefruit and eventually brown on both grapefruit and oranges. Pits

on oranges are usually less than Y^ inch in diameter, although

they may coalesce into larger areas. In Florida, early and midseason oranges are more susceptible to pitting than are the lateripening varieties of the Valencia type. The Pineapple variety is

the most susceptible. Smooth-skinned fruit is more likely to develop pitting than is coarse-skinned fruit. Small-sized fruits are

more susceptible than large ones.

Pitting of Freshly Harvested Fruit

Pitting as seen in the field and packinghouse differs markedly

from pitting that develops in storage. In the field the pits seen

on both oranges and grapefruit are small and rarely coalesce,

and the affected areas remain firm. Pits that develop soon after

harvest are usually not discolored (pi. 6, D), but they may coalesce

to form a large area of collapsed rind tissue. Pits on fruit in the

field or freshly harvested rarely lead to invasion by decay fungi.

Storage Pitting

Pits on fruit in storage or on the market after storage are

usually a symptom of chilling injury, which may occur at temperatures well above the actual freezing point of the fruit. These

depressed spots may not be discolored at first, but later they turn

tan-to-brown (pi. 7, E and G). Where they occur singly, they

are usually 14- to 1/2-inch in diameter. In severe pitting, a large

part of the surface may be affected. Softening beneath the pits

may lead to invasion by blue-mold, anthracnose, or stem-end rot

fungi (pi. 7, D). Severely pitted fruit may have an off-flavor even

when decay organisms are not involved. Pitting is not usually

observed before the fruit has been stored or in transit 2 to 4

weeks. Grapefruit harvested from September to January is more

susceptible to pitting than fruit harvested later. Brown staining
MARKET DISEASES OF CITRUS^ OTHER SUBTROPICAL FRUITS 33

and other forms of chilling injury may be associated with pitting

caused by low storage temperature.

A type of pitting of lemons known as peteca may develop in

storage. It is characterized by depressions with rounded edges.

The collapse begins in the albedo^ and the outer layer of the rind

sinks with little or no discoloration at first. The oil glands may

darken. In extreme cases the surface layer may collapse and

become discolored. Its occurrence seems to be largely determined

by previous orchard and climatic conditions. It is most common

on fruit picked in cold, wet seasons (pi. 6^ C).

Control measures

Pitting and other forms of rind breakdown of freshly harvested

fruit are best controlled by harvesting at prime maturity, careful

and prompt handling, avoiding over-brushing, and a good application of fruit wax.

Pitting in storage can be avoided or reduced by storing only

prime waxed fruit at recommended temperatures (table 1, p. 19)

and 87 to 92 percent relative humidity. Grapefruit may well

benefit from curing the fruit at 70° to 75° F. for several days

before putting it into colder storage.

(See 56, 61, 76, 87, llA, 116, 201, 208,)

Puffiness

Pufiiness in citrus fruits is a condition in which the rind becomes thickened, somewhat soft, loose, and separated from the

segments beneath. Affected fruits lose their natural shape after

packing and shipping. The loose rind sometimes cracks^ thus

affording easy entrance for the organisms causing blue-mold and

green-mold decay.

Puffiness is usually found in overripe fruit. In California

oranges, it is often associated with creasing, though fruit may

be puffy without being creased. Puffiness is exceedingly rare in

most varieties of Florida oranges but is common in tangerines,

Temple oranges, and other mandarin-type fruits (pi. 9, G). Fruits

may become puffy while on the tree, or this condition may develop

in storage after packing. The cause is apparently a loss of water

from the segments, which shrink and separate from the peel.

Overripe fruit that tends to be puffy at the time of packing

should be handled carefully and marketed promptly.

(See 76, 186, 208,)
34 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

Scab

Elsinoe fawcettii Bitanc. & Jenkins

Occurrence, symptoms, and effects

Scab is an important field disease in Florida, the Gulf States,

and other areas having moist summers, but is absent in California, Arizona, and countries having a semiarid climate. Scab

in the United States is the type known as sour orange scab, or

lemon scab. It was introduced in 1876 on the first Satsuma trees

brought to this country from Japan, where it had existed since

ancient times.

Considerable range in susceptibility to sour orange scab occurs

among the different kinds and varieties of citrus. Among commercial varieties in Florida, sour orange, Temple orange, lemon,

and some tangelos are very susceptible. Grapefruit, tangerine,

King orange, and Satsuma are generally less susceptible. Considerable resistance is shown by sweet oranges and Persian

limes, while Key hmes, citrons, Cleopatra, mandarin, and round

kumquats are immune.

Scab occurs on leaves, twigs, and fruits, but attacks only

young host tissues. Symptoms start as small translucent spots

which, as they grow older with the maturation of the host tissues,

become irregular scabby areas or warty protuberances ranging

in color from buff to dark olive-gray. These protuberances may

be single, or they may coalesce to form large raised patches of

gray or tan-colored scab (pL 4, E). Fruits severely infected while

young may become misshapen because of excessive development

of the warty outgrowths. On grapefruit, the infected areas tend

to be flatter and with maturity are merely scaly patches. These

patches may flake off and leave scar tissue similar to windscar

or other mechanical injuries. On mature grapefruit, the skin

around the scabby areas tends to remain green, a condition that

may also occur after melanose or scale-insect injury.

The disease affects only the skin of the fruit but makes it unsightly and, therefore, less valuable for fresh market. Since

infection takes place only when the fruit is small, there is no

danger of new infection after harvest. Areas affected by scab

are not invaded by other fruit-rotting organisms.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 35

Causal factors

Sour orange scab is caused by Elsinoe fawcettii Bitanc. &

Jenkins (Sphaceloma fawcettii Jenkins). The causal fungus overwinters on scabbed leaves and twigs and multiplies on the new

flushes of growth in the spring.

Two other types of scab affect citrus but are not known to

occur in North America, These are (1) sweet orange scab {Elsinoe

anstralis Bitanc. & Jenkins), which is serious in South America,

and (2) Tryon's scab [Sphaceloma fawcettii var. Scabiosa (McAlp. & Tryon) Jenkins] on lemons in Australia and Argentina.

Control measures

Since infection occurs only in the orchard, treatments after

harvest are of no value. Scab can be controlled by field application

of protective sprays.

(See ^, 25, 71, 73, 76, 122, 186, U7 ,201, 206, 208, 280,)

Sclerotium Rot

Sclerotium rolfsii Sacc.

A minor decay due to the soil fungus Sclerotium rolfsii has

been reported in the market on citrus fruits from Florida and

other Gulf States, Caribbean Islands, Israel, Italy, Brazil, China,

Japan, and some parts of Australia. Sclerotium rot is not found

on fruit from California or Arizona.

The decay on grapefruit and lemons is yellowish-green, slightly

darker than normal. On oranges it is dark brown with slightly

lighter margins. The fungus rots oranges and lemons at about

the same rate. At 65"^ to 75° F., the decay spreads within 2 to

3 weeks through most of a fruit. If the air is moist, an extensive

white, ñuífy mycelium forms on the surface. Small, spherical

sclerotia, yellow at first but deep brown or black later, % g inch

or less in diameter, are formed in great quantities on the surface

and sometimes in the albedo and core. The decay is fairly soft

and watery. Breaking down of the flesh extends into the core and

the juice sacs.

Because Sclerotium rolfsii is a soil inhabitant, fruits touching

the ground are usually the only ones affected. They should be
36 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

avoided, if possible, during picking. Use refrigeration to prevent

spread of the decay frona diseased to sound fruit during transit.

(See 79, 153, 208, 209,)

Septoria Spot

Septoria sp.

Occurrence, symptoms^ and eflfectg

Spots or pits caused by a species of Septoria, probably S. citri,

sometimes occur on lemons, grapefruit, and Valencia oranges in

California and other citrus areas, notably New South Wales,

Australia. Septoria spot is rarely seen on fruit on the market

in the United States and usually is of only minor importance

in the orchard.

The pits seen on fruit on the tree are usually i-ound, dark

brown, and sunken. They vary in size from %2 inch up to

% inch in diameter (pi. 4, D.). The pattern ranges from few and

scattered spots to numerous ones that coalesce, sometimes in

streaks similar to tear-staining or as scald-like areas, probably

associated with frost burns. The spots are surrounded at first

by a narrow green halo, which eventually turns reddish brown.

Eventually the pits extend deeply into the rind, which is discolored. Badly infected fruit develops off-flavor and usually falls

from the tree.

The fungus grows and sporulates freely on twigs and fruit

stems and on dead wood on or under the tree. The latter is the

primary source of infection to the fruit and leaves.

Causal factors

For years there was a general belief that septoria spot and

frost injury were associated and that frost injury was necessary

before the fungus could infect the fruit. Investigations in New

South Wales revealed that the septoria fungus must be established

in the rind before the frost and that it does not infect fruit

after frosting. Septoria spot develops quickly on fruit weakened

by frost but from prefrost infections.

Control measures

A zinc-copper-lime spray applied in early fall to citrus orchards

in interior areas in California protects against septoria spotting
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 37

and brown rot of fruit, as well as copper and zinc deficiency

of foliage.

(See 1, 136, 188, 1Í5, 208,)

Sour Rot

Geotrichum candidum Lk. ex Pers,

Occurrence, symptoms, and effects

Sour rot at its worst is one of the messiest and most unpleasant deteriorations of citrus fruit. The disease has been

reported from most areas of the world where citrus is grown.

It is primarily a disease of citrus fruit in storage or transit,

although fruit on trees may be affected. Sour rot is usually not

a disease of major industry-wide importance, as compared with

blue-mold and green-mold decays or the stem-end rots. However, the importance of sour rot may generally be underestimated

because initial infections are easily overgrown by other molds.

Sour rot is found most often on lemons and limes, since they

are often stored longer, but occurs as well on oranges, grapefruit, and other citrus. Ripe or overmature fruit is more susceptible to this decay than green or immature fruit. The disease

is more of a probleni during and after prolonged wet seasons.

Generally, lemons from coastal districts are particularly affected

by this disease. Heavy losses have occurred after long wet periods.

Causal factors

Sour rot is caused by the fungus Geotrichum candidum, formerly called Oospora citri-aurantii or Oidium citri-aurantiL This

fungus is widely distributed in soils and causes postharvest decay

in several crops. Primary source of sour rot infection is found

in the orchard. The surface of citrus fruit may become contaminated with geotrichum spores by soil contact, dust from

cultivation, or splash from soil during irrigation or rain. Lowhanging fruit has more geotrichum spores on rind surfaces than

does fruit higher in the tree.

Symptoms of the initial stages of sour rot are very similar

to those of green and blue molds, and the rots are often confused.

Infected fruit first shows a water-soaked spot, which enlarges

and eventually involves the whole fruit (pi. 3, A). The watersoaked areas are very easily punctured, are slightly raised above

the healthy adjacent surface, and are dark bufli-yellow colored.
38 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

The sour-rot fungus at first grows mainly inside the fruit. Later

a thin, water-soaked layer of compact cream-colored growth develops on the surface. The whole inside becomes a sour-smelling,

decomposed, often putrid, watery mass, which is very attractive

to fruit flies. Fruit with sour rot may decay completely in as

little as 5 days at 75 to 85° F. and high humidity. Not only does

the original infected fruit collapse, but neighboring fruit in the

package is infected by contact.

Control measures

Sour rot is not found frequently. Its development can be prevented by transport and storage at 40° F. However, lemons and

grapefruit held long at less than SO'' may develop physiologic

injuries. Although large numbers of fruit are contaminated with

geotrichum spores, infection cannot occur except through a wound

and during high humidity. Therefore, it is especially important

to avoid rind injuries during picking and packinghouse treatments. SOPP or soda ash in the wash water may aid in reducing

sour rot. Storage boxes that have contained sour-rot decayed

fruit should be sanitized with steam, formaldehyde, or similar

agents. Less sour rot develops in fruit shipped in vented than

in nonvented cartons. Geotrichum candidum is resistant to biphenyl and thiobendazole, and these chemicals cannot be expected

to give any protection.

(See S9, k8, 51, 63, 67, 76, 96, 117, 136, 208, 209, 231, 238,

289, 2Jf6.)

Stem-End Rot

Phomopsis citri Fawc.^ and Diplodia natalensis P. Evans ^

Occurrence, symptoms^ and eflFects

Stem-end rot caused by Phomopsis citri and Diplodia natalensis is a destructive and widely distributed disease of all citrus

fruits in the Gulf States, the West Indies, and other citrus-growing regions of the world that have high rainfall during the growing season. Stem-end rot is rarely seen in California and other

semiarid regions.

* The perfect stage, Diaporthe eitri Wolf.

^ The perfect stage, Physalospora rhodina (Berk, et Curt) Cke.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 39

Both forms are characterized by a softening of the rind and

underlying pulp. It usually begins at the stem end, although it

sometimes begins at injuries on the side or stylar end. Neither

form shows much discoloration in the early stages. Later the

affected rind turns tan to brown, and sometimes even black. At

room temperature, fruit infected with Diplodia will decay completely in 3 to 4 days after the first symptoms appear. The decayed

tissues do not shrink. The infection progresses rapidly down the

spongy central axis, usually reaching the stylar end much sooner

by this route than through the surface rind. There is frequently

a more rapid decay development in the rind along the lines that

mark the divisions between the segments of the pulp, giving an

appearance of "fingers'' connecting the rotted ends of the fruit

(pi. 3, B and C). There is usually a sour, fermented odor. Phomopsis decay is slower, and there is some shriveling of the decayed

tissue, which causes a shoulder or line of demarcation between

decayed and sound tissue (pi. 3, D and E). It likewise progresses

more rapidly down the core, but doesn't reach the stylar end

until the rind is two-thirds decayed. Fingers or streaks on the

outside of the fruit are seldom seen, due to the slower rate of

decay. The taste is fiat and somewhat bitter, and the odor is

unpleasantly rancid. The invaded pulp becomes mushy but is not

discolored. Affected fruits do not lose their shape unless subjected

to pressure. Surface growth is occasionally seen on fruit infected

with Phomopsis, but seldom on that with Diplodia before the

fruit mummifies. Immature citrus fruit is very resistant to stemend rot, whereas deadripe fruit is very susceptible.

Causal factors

The stem-end rot fungi flourish and form spores in or on dead

citrus bark. During rainy weather the spore crops are produced

and disseminated to the fruit. The fruit is first infected on the

stem button at some time during the growing season. Soon after

the fruit is clipped from the tree, the fungus begins growth from

the button into the rind and flesh.

Phomopsis and diplodia rots may occur in the same lots of

fruit, or both fungi may be isolated from the same fruit. Phomopsis occurs throughout the harvest season, whereas Diplodia is

more common during the autumn ethylene-degreening season and

in late spring after the return of warmer weather and frequent

rains. When both rots occur, an important factor in determining
40 AGRICULTURE HANDBOOK 398, U.S. DEFT. OF AGRICULTURE

which will predoniinate is temperature. The optimum temperature for growth of Diplodia is about 86° F., and that for Phomopsis about 73°. When grown on agar medium at room temperature,

Phomopsis grows relatively slowly and produces a fine-textured

white mycelium, and Diplodia produces a coarse, rapid-growing,

grayish-black mycelium.

Under certain conditions, stem-end rot may attack fruit on

the tree, causing it to drop. Usually, however, it shows up only

after harvest and becomes severe by the time the fruit reaches

the retailer or consumer. It is impossible to detect and cull out

fruit that may later develop stem-end rot, since at room temperature the rot does not develop until 10 to 20 days after harvest.

Control measures

Practical prevention of excessive loss from stem-end rot depends on several factors: prompt marketing of the fruit and

proper refrigeration during storage and transportation. Temperatures of 40° to 45° F. are as necessary for control of stemend rots in transit as for green-mold and blue-mold rots. In storage, 33° to 34° F. is desirable for control of all of these rots of

oranges. Due to peel injury and other effects of chilling, higher

temperatures must be used for tangerines, grapefruit, lemons,

limes, and certain hybrids.

Stem-end rot after the fruit is harvested has been markedly

reduced with various chemicals. Orthophenylphenol or its sodium

salt, thiabendazole, and biphenyl are recommended as postharvest

treatments.

Hot-water treatment (127° F. for 5 min.), applied just before

packing, may also help reduce decay.

Debuttoning of fruit at harvest is beneficial, because it removes

the source from which the initial infection may spread into otherwise sound fruit. Pulling of fruit of most varieties instead of

removing it with clippers is recommended for the same reason

and is extensively practiced in Florida. Some varieties at certain

maturities must be clipped because of the danger that the rind

around the button will be plugged (torn).

Pruning out dead limbs and twigs to diminish the sources of

infection is very helpful and is beneficial for melanose control

also, but usually it is not economically practical.

(See 11, 32, 36, 37, 38, 76, 113, 115, 136, 1^7,161, 165, 177, 178,

ISA, 200, 201, 202, 206, 208, 246, 2Í7, 2U9, 250, 251, 281, 28i,

286, 288,)
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 41

Stylar-End Breakdown

Occurrence, symptoms, and eff^îts

Tahiti (Persian) limes, as they approach maturity either on

the tree or after being picked, are susceptible to a collapse of

the rind. This most frequently occurs at the stylar or blossom

end of the fruit, but it may occur at other locations. This breakdown, which has been observed on lemons and other limes also,

is the most serious postharvest disorder or market defect of commercial limes.

Symptoms first appear at the base of the nipple or tip as a

grayish-tan, water-soaked spot. The affected area enlarges rapidly,

involving up to one third to one half of the fruit (pi. 6, G), The

affected area remains firm but becomes darker with age and

usually sinks below the healthy surface. There is often a partial

collapse of the ñesh beneath the breakdown and a water soaking

of the core tissue. Gum pockets and gum-filled vascular bundles

may be observed in the albedo and central axis. The area may be

quickly invaded by organisms such as Geotrichum, Aspergillus,

Gloeosporium, and Pénicillium, producing a stylar-end rot.

Causal factors

No organism has been associated with the early stages of this

disease. Its inception is considered to be physiological.

Control measures

Control of stylar-end breakdown of limes has been reported

after the use of ferbam and other organic fungicides used for

tar spot and scab control. Since no organism is involved, these

chemicals may provide nutrition (possibly iron) or be otherwise

beneficial to the physiology of the tree. Also, the disease may be

reduced by avoiding overmature fruit, by harvesting only in the

afternoon and under dry conditions, and by handling the fruit

carefully after harvest.

(See 81, lOi, 136, 1^7, 193, 201, 206, 208.)

Sunburn

On fruit of most citrus varieties, large areas of the rind may

be pitted all over, hard, flat, and much yellower or paler than

the rest of the surface. The pits, which are very small, have

resulted from collapse of the oil glands. In severe cases, the
42 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

fruit will be one-sided, with up to one-half of the fruit being

involved. The yellow surface may have a brown or gray center

where the surface cells have been killed. The flesh under the

affected area is dried out and contains little or no juice (pL 9, F).

Such fruit may become infected with various decay organisms.

It would normally be graded out before being packed.

Fruit on smaller trees is more frequently affected than fruit

on large trees, because of the unevenness of the foliage canopy.

Certain varieties, such as the Murcott Honey orange, are more

susceptible than others because their stiff branches and fruit

pedicels hold more of the fruit on the perimeter of the tree and

allow longer exposure to the direct rays of the sun.

Similar symptoms may result from spray injury, without any

contributory action by sunshine. Such affected areas may have

brown necrotic centers or brown necrotic pitted areas. The fruit

is not misshapen unless the injury occurs at an early stage of

development.

(See 136, 201, 208.)

Thrip Injury

Scirtothrips citri (Moult.) = Citrus thrips in California;

Frankliniella hispinosa (Morg.) and Chaetanaphothrips

orchidii (Moult.) in Florida

The damage done by thrips to citrus fruit is caused by the

feeding of both adults and larvae upon the fruit surface. They

may feed on either young or nearly mature fruit and foliage.

Thrip injury is most important on oranges but may occur on

other fruits. The most characteristic form is a roughened band

or corky ring around the stem or stylar end (pi. 5, F), caused

by feeding injury when the fruit was small. This type of injury

is more prevalent in California than elsewhere. It is caused by

S. citri in California, but may be produced by F. bispinosa in

Florida. Injury produced by orchid thrips (C, orchidii) is similar

in appearance to rust-mite russeting. It occurs as rings or roughened areas where two fruits are in direct contact or a leaf and

fruit touch, since these insects avoid direct sunlight and feed

in shaded areas.

Thrips generally do not cause sufficient damage to need specific

control. They are normally held in check by the sprays that

control rust mite and scale.

(See i, 88, 201, 208.) ^
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 43

Trichoderma Rot

Trichoderma viride Pers, ex Fr.^

Occurrence, symptoms, and effects

In some areas trichoderma rot probably rates second in importance after pénicillium green mold. In other areas, including

Florida and Texas, this decay is found only occasionally. Lemons

are attacked more often, and decay develops faster in them

than in grapefruit or oranges. Fruit maturity is not an important

factor in susceptibility to this decay, although fruit are more

susceptible after they have been off the tree for more than a

week.

Trichoderma viride enters fruit through injuries, usually at

the stem end. The deeper the injuries, the greater the chance

for infection. The fungus, under some conditions, can also spread

by contact v^ith infected fruit. T. viride is an important soilinhabiting decomposer of cellulose. It is able to grow from infected fruit into wooden storage boxes, and later to grow out

from the box into healthy fruit.

Citrus fruit rotted by T, viride turns brown to cocoa-brown

(pi. 3, F) and has a firm somewhat pliable texture as compared

to the soft, ^*colorless^* rot caused by the green mold, Pénicillium

digitatum, which secretes pectolytic enzymes. A coconut-like odor

is typical in trichoderma-decayed tissues. The decay develops

slowly and is very often overgrown by Pénicillium, If P. digitatum

does not take over, the whole fruit will become dark brown, but

will not soften or shrink. If the rotted fruit is kept moist and

in the dark, a white mycelium will soon appear. When trichoderma-infected fruit is exposed to light, yellow-green to dark-green

spores are produced, which somewhat resemble Pénicillium spores

(pL3, G).

Control measures

The same control measures are recommended for Trichoderma

as for Pénicillium, Injuries should be avoided and sanitation

practiced. The fungus should be completely removed from wooden

storage boxes, using steam, formaldehyde, or other disinfectants.

Also, the storage boxes can be protected from fungus invasion by

coatings of wax, resins, or plastics, or by lining the boxes with

^ The perfect stage, Hypocrea rufa Fr,.
44 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

plastic-coated paper. T\ viride is partly resistant to biphenyl,

the use of which only partly reduces spread of contact infections.

Shipping fruit in vented rather than nonvented cartons reduces

contact spread of trichoderma rot. The main protection, however, is achieved by refrigeration.

(See 2i, M, 76, 79, 82, 91, 92, 93, 96, 136, 208,)

Water Spot

Water spot is a disease that develops especially on mature

Washington navel oranges on the tree, after exposure to prolonged rainy or foggy weather. The earliest stage is a minute

cracking of the cuticle, usually near the navel, caused by a swelling of the underlying tissue when it absorbs water. It also develops on the shoulder of the fruit, where drops of water may

easily collect, and at or near wounds. If the wet weather continues, these affected areas enlarge, assume a water-soaked appearance, and are eventually invaded by decay organisms, chiefly

green mold or blue mold. Under extreme conditions, half or more

of the fruit on a tree may be ruined by this rind breakdown and

the rot that follows. Water spots that develop elsewhere than

at the navel usually start at bruises or skin breaks.

If the weather turns dry after the first stage of the spots has

developed, the water-soaked areas become brown, dry, and slightly

sunken (pi. 9, fí'). However, some of the blemished fruit may

escape notice during the harvesting and packing and so get into

the packed boxes. It may also happen that the spots are invaded

by fungi but are kept from decaying by the coming of dry weather.

When such fruit reaches the packinghouse, much of the external

fungus growth is removed by the brushes, and again the damaged

fruit may be packed along with sound fruit. In either of these

cases, the spots become a potential source of trouble during transit

and on the market, because of the danger of renewed growth

of the fungi through the weakened rind whenever conditions

become favorable.

Water spot is most common in groves sprayed with oil.

Delayed harvesting of the crop should be avoided, along with

careful orchard protection to eliminate fruit injury by insects

and freezing. Orchard applications of hormone sprays are reported to reduce the incidence and severity of this disorder.

(See 76, 136, 208.)
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 45

Wind Scarring

The surface of fruit may be injured when the fruit is rubbed

against twigs, leaves, or thorns by the wind. The resulting scars

reduce the grade of the fruit. If small green fruits are injured,

the damaged area develops a thin tan-to-silvery scar over a relatively large area as the fruit matures (pi. 5, G). Injury that

occurs later may be in the form of scratches, pits, or thorn

punctures (pi. 5, if), which usually heal over with corky scar

tissues.

Scars resulting from injuries when the fruit was small do not

act as avenues for decay organisms. However, fruit injured when

almost mature may decay because of invasion of the injured

tissues by Pénicillium, Phomopsis, or other rot fungi.

(See 201, 208,)

Miscellaneous Spotting and Discoloration

Oranges and other citrus fruit arriving on the market show

at times various kinds of spots and larger discolored areas of

the rind that are hard to relate to a definite cause. Most of these

imperfections are various shades of brown. Some are superficial,

while others are more or less sunken. Descriptions and illustrations have been published at various times attributing them to

such causes as improper coloring-room conditions, fumigation injury, cold temperatures, mechanical bruising, brush injury scarring, heat damage, chemical injury due to orchard sprays or

postharvest treatments, unusual weather conditions, or combinations of these, which cause a surface necrosis or a physiological

breakdown of the rind tissues (pis. 8 and 9).

The difficulty, from the market point of view, is that in many

instances the history of the fruit is not known and cannot be

obtained accurately. Consequently, definite diagnosis of the cause

cannot be made. These maladies, however, are observed more

frequently at the beginning of the shipping season when the

fruit is somewhat immature and the rind is more tender and

subject to injury. These afifected fruit may become infected with

various decay fungi or may remain unchanged during the storage

and marketing period.

(See 136, 208, 28Í.)
46 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

AVOCADOS

Anthracnose (Black Spot)

Colletotrichum gloeosporioides (Penz.) Sacc.

Occurrence, symptoms, and effects

Anthracnose, or black spot, is the most frequently observed rot

of softening avocados on the market. This decay may be found

on fruit from all commercial growing areas and of all commercial

varieties.

Small, light brown, mostly circular, discolorations of the skin

first appear scattered over the surface of the fruit. As they

enlarge rapidly to 14- or i/^-inch diameter, the color changes

through light brown at the edge, to dark brown, and black or

greenish black in the center of the spot. Centers of the spots

may be slightly sunken. Surfaces of the larger spots, 1 to 2 inches

across, frequently appear zonated, cracked, or fissured, A single

lesion may enlarge to cover the entire side of a fruit, or scattered

smaller lesions may coalesce to cover large surface areas. Large

decayed areas are found only on overripe fruit. If the fruit is in

a moist atmosphere, the fungus forms pink waxy spore masses

on the surface of the spots (pi. 10, A). These spore masses may

merge as spots coalesce, and they turn black with age.

The decay penetrates rapidly and deeply into the flesh beneath

the spots. It forms a greenish-black, fairly firm, globular decayed

mass that can be easily and cleanly separated from the healthy

meat, leaving a fairly clean cavity. Eventually the decay extends

to the seed. Anthracnose decay lacks the characteristic rancid

odor of dothiorella rot, and it is not as moist. The black color

of the spots and the decay immediately beneath are distinctive

features of anthracnose.

Causal factors

The causal fungus, Colletotrichum gloeosporioides (Penz.) Sacc.

causes anthracnose decays of mangos, papayas, and citrus fruits.

In avocados the fungus commonly grows on dead twigs and in

dead spots on leaves and fruit. This fungus is a weak parasite.

It is unable to penetrate and grow actively in healthy, uninjured,

growing fruits, but it may establish itself as a latent infection

on the fruit, especially at the lenticels. Later, as the fruit becomes

mature and softens, it is able to develop. As avocado fruits ap-
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 47

proach maturity, the fungus establishes itself actively through

dead areas or cracks in the rind caused by other fungi, mechanical

injuries, or insects. In Florida, anthracnose commonly infects

fruit through cercospora spot or sphaceloma scab lesions.

Control measures

Anthracnose decay is controlled by preventing skin breaks or

injuries to fruit. A good field spray program to control insects,

cercospora spot, and sphaceloma scab is helpful. Injury to fruit

during picking and handling should also be avoided. If avocados

are to be held in storage for several weeks, anthracnose decay

often becomes important as the fruits mature and soften. Anthracnose is not usually troublesome if fruit is held at 45° F.

However, many avocado varieties are subject to chilling injury,

and they should be stored at 55°.

(See 118, 125, 185, 187, 211, 212, 215, 217, 222, 225, 25^, 287,

291, 292.)

Avocado Scab

Sphaceloma perseae Jenkins

Occurrence, symptoms, and effects

Avocado scab is one of the most important diseases of avocado

fruit and foliage in Florida and in several important commercial

growing areas of Latin America and South Africa. It has not

been found in California or the Hawaiian Islands. Avocado

varieties vary in susceptibility to scab. Lula is the most susceptible commercial variety; Hall, Fuerte, Booth 8, Booth 7, and

Taylor are moderately susceptible; while Fuchs, Pollock, Booth

1, and Waldin are quite resistant.

The disease occurs on fruit as raised, circular-to-oval, darkbrown to purplish-brown corky spots. These spots are scattered,

or may coalesce to give the fruit a russeted appearance, or may

form irregular extended areas sometimes involving practically

the entire surface of the fruit (pi. 10, B), Scabby, deforming

lesions are also formed on leaves, leaf petioles, and twigs. On

mature fruit the injury is confined to the outer surface, and

eating quality is not impaired by this disease. However, fruit

appearance can be very unattractive, and in severe cases the

fruit may be so undersized or misshapen as to rate as culls. Other

fungi may gain entrance through cracks in scab blemishes and
48 AGRICULTUEE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

cause deeay. Avocado scab itself does not develop or spread in

transit or storage.

Causal factors

The fungus causing this disease, Sphaceloma perseae, is capable of entering young succulent tissue of avocado foliage and

fruit, forming definite spots from which it grows and produces

spores. From these centers the disease is spread in rain drops

or dew drip, by insect carriers, or wind. It is carried over from

one season to another on leaf and stem lesions. The critical period

for fruit infection is from the time the petals fall until fruit has

attained a third or half of its normal development.

Avocado scab is very similar to citrus scab in general appearance and in the reaction of its host. The fungi causing these two

diseases were once considered identical, but they are now recognized as distinct morphologically and culturally.

Control measureg

Avocado scab is controlled with field sprays of copper-containing fungicides.

(See 123, 124, 155, 208, 212, 213, 21U, 218, 221, 223, 225, 25U,

287, 292.)

Cercospora Spot (Blotch)

Cercospora purpurea Cke.

Occurrence, symptoms, and effects

Cercospora spot or blotch is an important disease of avocado

in Florida; it occurs in several areas in Latin America also. In

Florida it is widely distributed throughout the avocado-producing

areas. No commercial varieties have been found immune to cercospora spot once the fungus has become firmly established in the

trees, but the disease is less severe and more easily controlled

on Fuchs and Pollock than on other commercial varieties. This

disease occurs on leaves and young stems as well as fruit, but it

is of economic importance chiefly as a fruit disease.

Spots on the fruit appear as small scattered greenish-white

dots, which later develop into slightly sunken, brown-to-dark-
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 49

brown spots of definite outline but irregular shape (pi. 10, C),

Characteristic short, gray, spore-bearing tufts of fungus may

develop on the surface of these spots. These spots may increase

in size to Va- or 14-inch in diameter and finally develop into circular areas of hard brown dead tissues with a cracked or fissured

surface. Spots frequently occur in groups on the surface of the

fruit, or coalesce to form irregular areas of dead rind tissue

deeply fissured by surface cracks. By itself this disease spoils

only the appearance of fruit, as the fungus is limited to rind

tissue and does not penetrate the flesh. However, tissues killed

by the fungus and the cracks made in the rind allow other fungi,

especially the anthracnose fungus, to enter and decay the ripening

fruit.

Causal factors

The fungus Cercospora purpurea does not require a break in

the skin to enter. It can attack avocado fruit at any stage of its

development on the tree. The fungus is carried over from one

season to the next on old leaf infections. If control measures are

not taken, the disease tends to become progressively more serious

in an orchard.

Control measures

Cercospora spot can be controlled by timely applications of

various copper sprays to developing fruit on the tree. Methods

that control cercospora spot usually control anthracnose also.

(See 208, 215, 216, 217, 218, 219, 220, 223, 22A, 225, 25hy 287,

292,)

Flesh Darkening

Avocado fruits of different varieties vary in the normal color

of their flesh. In certain varieties the flesh is sometimes rather

gray, and during certain seasons, possibly because of abnormal

conditions of growth, the flesh of commercial varieties may be

unusually dark. The flesh may also darken in overripe or very

soft fruit or when the seed begins to grow. On the market, hard

dark areas are sometimes found in fruit from Florida and the

West Indies believed to have grown on seedling trees. Flesh discoloration is also commonly caused by chilling, freezing, or heating the fruit.
50 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

Chilling Injury

In general, chilling injury occurs when the fruit is stored

below a critical temperature. This critical temperature varies

with variety, fruit maturity, season, and length of time the fruit

is held in storage. Some varieties can withstand temperatures

as low as 36° F. for several weeks without injury. Other varieties

are severely injured if held below öS"". Avocados of the West

Indian race are more susceptible to chilling injury than those of

the Guatemalan and Mexican races or hybrid varieties. Generally,

most avocados from California can be stored for a month or

longer at 40°, except the Fuerte, which should be stored at 45°.

Florida avocados vary in cold susceptibility. Cold-tolerant varieties such as Booth 1, Booth 8, Lula, and Taylor may be stored

for more than a month at 40°. Cold-intolerant varieties, such as

Fuchs, Pollock, and Waldin may eventually show chilling injury

even at 55°. Booth 7 is intermediate in cold tolerance and may

be held at 55° without injury or at 40° to 45° for 2 weeks before

chilling injury develops. Fruits just beginning to soften are more

susceptible to chilling injury than green, unripe fruit. It is

desirable to store avocados as cool as possible to retard ripening

(softening) and restrict development of anthracnose and other

storage decays.

Chilling injury in avocados is characterized by several symptoms that may occur in combination or singly in different varieties. The most common symptom is a grayish-brown discoloration

of the flesh, especially in the vascular tissues (pi. 10, E). In slightly

injured fruit, the discoloration may occur in inconspicuous trace

areas in the seed cavity or in vascular tissues only. In more severe

cases, all the flesh is discolored. In very severe cases, abnormal

ripening, development of undesirable flavors and odors, pitting,

and a scald-like browning or darkening of the skin commonly

occur. Sometimes fruit appears normal while held at the storage

temperature but shows chilling injury when allowed to soften

at higher temperatures.

The freezing points of a number of varieties of avocado fruit

have been reported to range between 29.1° and 31.5° F. Immature

and partly mature fruits may freeze at a slightly higher temperature. If the fruit freezes on the tree or in storage before it softens,

the flesh remains tough and rubbery and becomes penetrated

by many small cracks.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 51

Heat Injury

Heat may damage picked avocados at temperatures as low as

77° F. if the fruit is held at this temperature very long. Relatively

short exposures to temperatures above 86° after picking v^ill

prevent fruit from softening normally and cause it to turn

black. The best ripening temperature for all varieties of avocados

has been reported to be 60°, although temperatures of 65° and

70° are also very good. Avocados ripened at 80° are usually

acceptable but generally poorer in appearance and flavor than

those softened at lower temperatures. At 80°, rapid and occasionally uneven softening may occur, decay and discoloration may

appear, and some fruit may be unpalatable because of ofF-flavors.

Small brown spots appear on the skin, and the flesh darkens.

At 90°, a scald-like discoloration of the skin may occur, and the

flesh becomes rubbery. Sometimes avocados held at 85° and 90°

require longer to soften than fruit held at 80° or lower.

(See 2, Jf5, 70, 105, 118, 157, 159, 180, 181,188, 189, 208, 269,

270, 277.)

Rhizopus Rot

Rhizopus stolonifer (Ehr. ex Fr.) Lind

Rhizopus rot is the most rapidly developing decay of ripe

avocados at room temperature. It is not found on the fruit until

it begins to soften. It is fairly common on roughly handled fruit

ripened at high temperatures. The decayed area is extensive,

dark brown, and, if the atmosphere is moist, covered with a

coarse white-to-gray mycelium bearing the typical spherical black

sporangia. If the atmosphere is dry, little surface mold growth

will occur, and the sporangia will be borne on short tufts in

depressions or breaks in the skin. Decayed tissues are collapsed

and watery but are held together by the tough mycelial threads of

the fungus. These can be detected with the tongue when the tissue

is tasted. Aft'ected fruits usually become cracked and exude an

ambercolored liquid. Flesh pulls easily from the seed and has a

peculiar and unpleasant odor.

Rhizopus soft rots also occur in peaches, strawberries, and a

number of other fruits and vegetables. In avocado fruit, it enters

at skin breaks or at the stem scar if the fruit has been pulled
52 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

from the tree. The fungus develops most rapidly at temperatures

between 70° and 85° F. At 50° there is little danger of new

infections being initiated, and at about 45° development ceases

altogether. Control measures consist of carefully picking and

handling of the fruit to avoid injuries to the skin, cooling of the

ripe fruit to 50° or lower, and preventing fruit from getting wet.

(See 118, 208.)

Stem-End Rots

Species of Diplodia^ Phomopsis^ Dothiorella

These rots of avocado fruit start at the stem end and develop

as the fruit softens. Considerable losses occur in shipments from

Florida and the West Indies. In typical stem-end rots the decay

begins at the stem end and proceeds rather uniformly toward the

blossom end, finally involving the whole fruit. The rot begins as

a small ring of affected tissue, dark brown in color and of firm

texture. Except for discoloration, there is very little external

change, and the surface remains firm and smooth. Progress of

the rot may be more rapid near the rind, but the ñesh is rapidly

invaded down to the seed, becoming dark to black, at first soft and

spongy, and later more or less firm. Later a surface growth of

short, felt-like fungus mass appears on the fruit, varying in

color and amount with the fungus causing the rot (pi. 10, D).

Three fungi can cause stem-end rots. The three kinds of rots

are very similar in general appearance in the early stages, and

one description will apply to all. The fungus most commonly

associated with stem-end rots is Diplodia, usually D. natalensis

P. Evans, although a species of Phomopsis and a species of

Dothiorella are frequently found.

No special control measures appear to be necessary, if fruit

free of decay and blemishes is selected for storage and kept

refrigerated within safe limits.

(See 89, 105, 118, 119, 208, 225, 254, 268, 289, 290, 291, 292,

293.)
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 53

BANANAS

Anthracnose

Gloeosporium musarum Cke. & Mass.

Occurrence, symptoms, and effects

Anthracnose or gloeosporium fruit rot is probably the most

common market disease of bananas. Primary infection occurs

either on the plantation when the fruit is very young or during

the harvest, local transport, and loading of the mature green

fruit. A secondary infection may occur during transport or after

the fruit is in the ripening room. Manifestations of the disease

include a finger-stalk rot, the characteristic spotting and later

general blackening of the peel, and tip rot. The disease also has

a role in main-stalk disorders and crown rot of boxed bananas.

The first two types may become evident during transport, but

the greatest development of all types of anthracnose occurs in

the ripening room or afterward. Most commercial varieties are

subject to infection, with the Gros Michel less susceptible than

the Lacatan, Cavendish, and Robusta.

Disease symptoms may result from wound-induced infections

after harvest or from latent infections of the immature fruit.

Wound-induced infections, which occur during the handling of

fruit from plantation to ship's hold, cause finger-stalk rot and

spotting of green and turning fruit.

Finger-stalk roí.—Twisting, bruising, scarring, or pressure

injury to the individual finger-stalk is usually followed by infection of the tissues with anthracnose or other wound fungi.

The affected area first becomes brown in color, then slowly enlarges to involve the entire finger and turns black. The rot may

progress during long refrigerated transport to the extent that

fingers drop off when the stems are discharged at destination.

This condition is further accelerated by the higher temperatures

in the ripening room. Detached fruit may be sound, but usually

the rot has spread to the edible pulp.
54 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

Anthracnose spotting—^Infection enters through scars or other

small peel injuries common to harvested green bananas. On green

fruit, very small, often lenticular, slightly sunken brown spots

with orange-yellow borders occur generally over the surface of

the fruit, after 8 to 10 days in refrigerated storage (pi. 11, A),

In the ripening room they rapidly increase in size to an inch or

more in diameter, may coalesce, and turn black. The discoloration

is largely confined to the peel, with little involvement of the

underlying pulp.

The latent type of anthracnose infection occurs when the fingers

are first exposed on the plant. The infection remains symptomless

in fruit from most producing areas until final maturity is reached

in the ripening room or in marketing channels, a period of about

90 days. Latent anthracnose is usually associated with overripe

fruit. It can be minimized by prompt marketing of the fruit soon

after its color changes from green to yellow. It is of much less

economic importance than infections after postharvest injuries.

Ripe-fruit ro¿.—-The symptoms are similar to those described

for the late stages of anthracnose spotting. Superficial brown

spots or patches turn black, enlarge, and coalesce, so that the

entire peel surface may be involved along with some of the

underlying pulp.

Tip roí.—This type of anthracnose also appears when the

fruit is turning yellow. A latent infection in the diseased flower

remnants on the tip-end is activated by advancing maturity and

spreads slowly to the adjacent peel and pulp. The affected tip,

up to one inch, darkens in color and is separated from the sound

yellow peel by a narrow, water-soaked, greenish-brown transition

ring. Eventually the underlying pulp decays completely.

One characteristic common to all types of anthracnose in their

late stage is the black color of the affected areas, along with the

visible production of pink-to-red masses of spores that later

change to gray or black (pL 11, A). Spore masses are usually

accompanied by a scant, white growth of aerial mycelium.

Causal factors

The various types of anthracnose, known under several common names, are caused by Gloeosporium musariim, a fungus reported from every banana-producing area in the world. On the

plantation the fungus exists saprophytically on the sheaths of

dead and dying banana leaves and trash, where spore masses are

produced in abundance. The spores are dispersed by rain, dew,
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 55

and wind so they are always present for either latent infection

of very young fruit or wound infection of harvested fruit.

Control measures

Control or reduction of anthracnose depends on following a

number of steps in a more or less standard procedure for handling

bananas from the plantation to the retail store. (1) The newly

cut bunches are immediately bagged in perforated polyethylene

film to minimize bruising and infection, (2) The cut ends of

main stalks are treated with a fungicide and may be retrimmed

and retreated immediately before loading aboard ship. (3) Exposure of harvested bunches to tropical temperatures is limited

to 30 hours or less. (4) Cooling of fruit to desired temperatures

in the ship's hold is done promptly, and the temperature is carefully maintained during ocean and land transport. (5) At destination the fruit is ripened expeditiously under exact limits of temperature and relative humidity before delivery to the retail store.

(6) The ripening room is sprayed regularly with a freshly mixed

5 percent solution of sodium hypochlorite before each shipment

of fruit is received.

(See 167, 168, 208, 272.)

Botryodiplodia Fruit Rot

Botryodiplodia theobromae Pat.

Occurrence, symploms, and efifecls

Botryodiplodia fruit rot is one of the most serious market

diseases of bananas. The causal fungus is widely established in

the tropics as a wound parasite of most commercial varieties of

bananas and other hosts. On bananas it is capable of causing a

main-stalk rot, crown rot, fingerstalk rot, and tip rot. The banana

fruit can be infected either in the field or after harvest, the

decay becomes evident either in transport or in the ripening

room.

Main-stalk rot,—An ideal entry point for infection by Botryodiplodia is the cut end of the main stalk, where the fungus

grows rapidly. The first symptom is a water-soaked appearance

of the affected area, followed by blackening, softening, and splitting of the infected stem. A grayish-green mycelial mat develops

over the affected area if the relative humidity is high, and later

fruiting bodies (pycnidia) cover the mat.
56 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

Croivn rot,—Symptoms are similar to those described under

main-stalk rot. The same tissues are involved, but an even greater

area of wounded tissue has been exposed by dehanding.

Finger-stalk rot.—Botryodiplodia infection of the main-stalk

and crown tissues penetrates through the cushion and infects the

finger stalks. The infection causes watersoaking and blackening

of the finger stalks, after which the fingers ripen prematurely and

drop off.

Tip rot.—This phase of the disease shows up in the ripening

room. The infection originates in or just below the ñower remnants on the tip end of the fruity and progresses uniformly from

the tip. It is accompanied by a brownish-black discoloration and

softening of the involved pulp. Whole fingers may be rotted,

with the pulp changing to a semiliquid with a sweetish odor. The

peel acquires a black, wrinkled appearance and becomes covered

with pycnidia. Secondary infection of injured fingers and bruised

areas may occur in the ripening room (pi. 11, ß).

Causal factors

The fungus, Botryodiplodia ¿/^eo&romae, formerly known as

Diplodia musae, is the cause of this fruit rot. The source of

infection is always present on fallen immature bunches and plant

debris common to the banana plantation. The banana can be

infected over a long period, ranging from small immature fingers

to harvested bunches at commercial maturity. The fungus grows

rapidly at tropical temperatures. During hot weather with abundant moisture in the producing area, the harvested fruit can be

expected to develop botryodiplodia rot during its transport and

ripening.

Control measures

Rapid cooling of the harvested fruit to 53° to 56° F. affords

protection from Botryodiplodia infections. Resumption of growth

of the fungus in the higher temperatures of the ripening room

makes prompt ripening and marketing mandatory when this

fruit rot is involved. (See control measures under Anthracnose.)

(See 86, 272.)
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 57

Chilling Injury

Occurrence, symptoms, and effects

The banana fruit is probably, of all fruits and vegetables,

most susceptible to chilling or low-temperature injury. This condition results whenever bananas, either unharvested or harvested,

are exposed to low but not freezing temperatures for relatively

short periods. Carrying temperatures during ocean and destination transport are especially critical in that they must be low

enough to delay the start of ripening and retard the growth of

incipient infections but avoid chilling injury. Slightly chilled

bananas may be ripened and marketed with little difficulty, but

those which are more severely chilled are either discounted or

dumped.

Chilling is evidenced by internal and external symptoms but

is mainly a peel injury. Both green and ripe bananas are affected,

but the symptoms become most conspicuous when the fruit is in

the ripening room. In chilled green fruit, some of the surface

cells in the peel are killed, become discolored by oxidation, and

later darken to a characteristic '*smoky" or dull appearance.

Before darkening occurs, dark-green, water-soaked areas, sometimes involving the entire peel surface, are visible on the peel

of severely chilled green bananas. External symptoms are masked

on less severely chilled green and ripening fruit. An examination of the subepidermal tissues reveals dark-brown streaks (pi.

11, E). Also, a lateral cut through the fruit shows browning of

the vascular bundles arranged in a concentric ring under the

peel (pi, 11, F). Slight chilling of green fruit is difficult to recognize. In such fruit, latex exudation from a broken finger or

cut wound in the peel is greatly reduced and tends to be clear

instead of milky or cloudy. The pulp is not affected and will

ripen normally.

Chilled fruit is more sensitive to mechanical injury during

handling than normal fruit, in that finger marks and other

bruises later become discolored.

Ripening in chilled fruit is greatly delayed and is evidenced

by a dull, smoky, yellow peel color. In severely chilled fruit the

peel becomes entirely brown and eventually turns black. Other
58 AGRICULTURE HANDBOOK 398, U.S. DEPT, OF AGRICULTURE

symptoms of chilling in ripening fruit, varying somewhat with

variety, include loss of banana flavor and hardening of the central core (placenta) in the edible pulp.

Ripe bananas can be chilled by prolonged exposure to temperatures below 50° F. (refrigerated display case or home refrigerator). Such fruit quickly develops the characteristic dull appearance of chilled bananas, and the peel later becomes dark brown.

Likewise, continuous exposure to sunlight will darken the peel

of ripe fruit.

Causal factors

Factors involved in chilling include the maturity and condition

of the fruit, the minimum temperature, and the duration of the

exposure. The less mature and thin fruits are more susceptible

to low temperatures than the more mature and full fruits of the

same variety. In general, a 12-hour exposure at any temperature

below 45° F. in still air causes chilling injury in most varieties,

regardless of the stage of maturity.

Gontrol measures

Precise temperature, relative humidity, and ethylene gas schedules have been developed and are used by the industry for the

transportation and ripening of the different varieties of bananas.

Minimum transportation temperatures for periods up to 12 and

18 days range from SS*" F. for Gros Michel and Dwarf Cavendish

to 56° for Lacatan and Giant Cavendish. Most banana ripening

rooms are operated in a temperature range of 55° to 68°, depending on the maturity at arrival and the demand for ripe

fruit.

(See 157, 272.)

Crown Rot

Occurrence, symptoms^ and effects

The banana trade uses the name "crown rot'' to designate the

decay that develops on the crown surfaces of boxed bananas. The

rot is an important problem with boxed bananas from Central

and South America. Most commercial varieties are susceptible to

the disorder.

The rot is limited mainly to the crescentic cushion or crown,

but in severe cases the finger stalks and fingers are involved.

The decay in the crown tissues causes the affected area to darken
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 59

in color and become covered with mold growth. Its presence in

a severe form in the crown tissues may cause some finger dropping and make the fruit hard to handle. Also, the presence of

surface mold growth, even without any decay, detracts from the

eye appeal of the fruit.

Causal factors

Crown rot can be caused by several fungi acting separately or

in some instances by a mixture of two or more fungi. These

include Botryodiplodia theobromae, Thielaviopsis paradoxa, Gloeosporium musarum, Deightoniella torulosa, Fusariurn roseum, and

Verticillium theobromae.

Control measures

The fungi responsible for crown rot, all of which may be

found on the fruit in the field, have been known for many years

as wound parasites on bananas. The increased wound area resulting from dehanding the bananas increases the importance of

these fungi. Protection of the exposed wound areas by means

of a chemical or possibly a hot-water treatment is a possibility

for control. (See control measures under Anthracnose.)

(See 86, 266, 272,)

Pitting

Piricularia grísea (Cke.) Sacc.

Occurrence, symptoms^ and effects

Pitting is an important disease of bananas on the plantation

and after arrival at destination. The severity of the disease can

increase during the transport and ripening of the fruit. At peak

severity, pitting can cause apparently clean fruit to become unsalable during its short stay in the ripening room. The disorder

was first called "Johnston fruit-spot,'' but later it was recognized

as a fungus disease. Pitting occurs usually on the Dwarf and

Giant Cavendish varieties but has been reported on other varieties

including the Gros Michel. Reporting countries are numerous and

worldwide, ranging from Costa Rica to Queensland, Australia.

Pitting occurs mainly on the fruit but may involve the finger

stalk and cushion. Usually symptoms do not appear until the

fruit is more than 70 days old, it may not become evident until
60 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

after harvest or later. Symptoms in the field and on the market

are similar.

During ripeningj the individual pit first appears as a faint,

reddish-brown, depressed ring, about i/g inch in diameter, with

a small dark spot in the middle of a central area that is not yet

sunken. Within 24 to 36 hours this central area becomes sunken

and acquires the characteristic dark-brown-to-black color. The

diameter of the pit is the same as that of the original depressed

ring and may measure up to nearly 14 inch (pi. 11, C). Individual pits may coalesce. Pitting on the fruit may extend deeply

into the peel but does not involve the pulp.

Finger-stalk infections cause some fingers to drop and provide

entry points for invasion by other fungi, i.e., Gloeosporkim

musarum, Botryodiplodia theobromae, Fusarium spp., and others.

Causal factors

The causal fungus Piricularia grisea sporulates on decaying

transition leaves and flower bracts. The young fruit are infected

several weeks after shooting, but symptoms of the disease are

not evident until full maturity.

The causal organism grows best at temperatures of 75° to 89° F,

It is little retarded at 55°, at which tempei'ature additional pits

may develop on stored fruit.

Control measures

Pitting is a disease of plantation origin, but the symptoms are

not evident until time of harvest. The number of pits continue

to increase during transportation and storage. Effective plantation control methods have not been devised. Rejection of affected

fruit at time of harvest is a practical method of reducing losses

during later handling of the fruit,

(See 19, 171, 208:)

Speckle

Deightoniella torulosa (Syd.) M. B. Ell.

Occurrence, syniplonis, and effects

Speckle fruit-spot, recently described as a fungus disease on

Jamaican bananas, and speckling, long thought in Central America

to be a physiological disease, are probably the same disorder.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 61

If SO, it is a widespread disease that has been found on many

commercial varieties of bananas including the Gros Michel and

Lacatan. Severely speckled fruit is graded out on the plantation,

but fruit less severely affected is often shipped if market conditions are favorable. Thus, speckle is important both on the

plantation and market.

Speckle lesions occur on young, green fruit in the field and

become more numerous with maturity. The spot is nearly round,

with a reddish-brown or black center and a darker green, watersoaked halo. The spots range up to 1/16 inch in diameter, and

different sizes may be found on the same finger. They are most

numerous on the inside of the fingers and toward the tips, where

they may coalesce. Symptoms are fully developed within 7 days

after infection. They vary slightly, depending on the source and

age of fruit.

The disease attacks only the peel, which impairs the attractiveness of the fruit. It causes no decay, nor does it affect the ripening or eating qualities.

Causal factors

Speckle is caused by Deightoniella torulosa, a fungus reported

from many banana-growing countries. It occurs usually as a common saprophyte on dead or dying banana leaves. It previously

had been described as the cause of two plantation diseases, blackspot on the banana leaf and black-tip disease on fruit. The main

source of infection is reported to be from dead leaves hanging from

the pseudostem of the banana plant. Spores are produced in

abundance during heavy and continuous rains. The peel of the

fruit is susceptible to infection from shortly after shooting to

nearly full field maturity.

Control measures

Speckle fruit-spot is a disease of plantation origin, and symptoms are fully developed before the bananas arrive at destination. Rejection of severely affected fruit on the plantation and

at ports of cargo loading and discharge should eliminate the

undesirable grades. Control measures on the plantation may

include (1) fungicidal sprays applied directly to the bunches;

(2) covering the individual stem with a plastic bag from shortly

after shooting to harvest; and (3) removing and destroying

the dead banana leaves and trash two or three times a year.
62 AGRICULTURE HANDBOOK 398, U.S. DEPT, OP AGRICULTURE

The latter method effectively reduces the disease and is probably the cheapest and most practical control measure.

(See 169, 170, 172, 272,)

Thîelavîopsîs Stalk Rot

Ceratocystis paradoxa (Dade) C. Moreau

Thielaviopsis paradoxa (De Seyn«) Hoehn.

Occurrence^ symptoms, and effects

Thielaviopsis stalk rot is nearly as destructive as botryodiplodia

fruit rot in the marketing of bananas from some areas. The

causal fungus is a wound parasite. It attacks bananas and other

tropical hosts and is the cause of black rot of pineapples. On

the Gros Michel and other varieties of bananas it is active as a

main-stalk rot and finger-stalk rot. The infection occurs on the

plantation and after harvest, but the symptoms develop when the

fruit is in transport and in the ripening room. Thielaviopsis fruit

rot is responsible for most of the "neck rot'* losses in ripening

rooms in the United States.

Main-stalk rot.—^The mode of infection of the cut end is similar

to that described for Botryodiplodia. The affected area blackens

and becomes soft and watersoaked in appearance. Under humid

conditions, a cobweb-like mass of dark mycelium develops over

the epidermis. The fungus grows extremely fast in the mainstalk tissues, v/hich are rapidly destroyed.

Finger-stalk rot—-The invading fungus continues from the

main stalk through the cushion to infect the finger-stalks and

fingers (pi. 11, D), The stalks blacken in color and may show

outgrowing webs of mycelium. The peel acquires an uneven black

color, and the pulp becomes dark brown and soft. The infection

of the finger tips results in finger dropping and premature ripening, characteristic of both Thielaviopsis and Botryodiplodia.

Causal factors

The decay in question is caused by the fungus Thielaviopsis

paradoxa. The finger-stalk decay phase of Thielaviopsis, Botryodiplodia, and other fungi is called by the trade '*neck rot.'* Possibly the term **black neck rot" would limit the group to the two

fungi listed.

T. paradoxa and B. theobromae are similar in many respects.

The information under Causal Factors for Botryodiplodia Fruit
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 63

Rot applies to Thielaviopsis. Both fungi are rapid growers and

can produce active decay before the bananas are cooled in the

holds of the ship. Neither is retarded greatly by moderate refrigerated temperatures, especially T. paradoxa, which continues

growth at 58° F. (See control measures under Anthracnose and

Botryodiplodia Fruit Rot.)

(See 86, P4, 272.)

FIGS

Alternaría Rot

Alternaría tenuis Auct.

One of the chief causes of loss in fresh figs is a surface spotting and rot caused by Alternaría ternas, (Also see Cladosporium

Spot.) It is found on all the important varieties and on fruit

from the Atlantic, Gulf, and Pacific coast states.

Alternaría causes small, circular, brown-to-black spots scattered

over the fruit surface (pi. 12, A, ß, and C). Decay is shallow

on immature fruit, but it penetrates deeper with maturity. The

fungus is first evident as a surface growth of small, grayishwhite tufts of mycelium. At this stage it is often called "mildew.**

The mycelium soon darkens to an olivaceous color or even darker,

and the spots may enlarge to a diameter of l^ or i^ inch. At first

the fungus appears to have but a slight attachment to the skin

and sometimes can be rubbed off with little evidence of injury,

but as the spots enlarge and the tissue beneath becomes slightly

sunken, any attempt to remove the fungus removes the skin also.

Alternaría spotting occurs on fruit on the tree as well as on

fruit in transit, held at the cannery, or at the market. The

disease is confined largely to fully ripe fruit. The fungus is

favored by cracks in the skin and by the sugary solution often

found on the surface of figs. Infection can occur in the field or

during harvesting and shipping. Other fungi, especially Cladosporium and Botrytis, are often associated with Alternaría in

these surface spots.

High humidity tends to increase spotting, but storage at low

humidity may cause an undesirable shriveling of the fruit. A

rain before or during harvest will greatly increase the incidence

of this disease in the orchard, with resultant carryover into market

fruit. Low-temperature storage offers the best means of controlling alternaría spot and rot. Figs that are promptly precooled
64 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

after harvest and kept at a temperature below 45° to 50° F. in

transit are not likely to become seriously affected during the

usual marketing period. Sanitation of picking boxes by dipping

in fungicidal solutions, or lining the boxes with clean paper,

helps reduce postharvest infections. Preharvest infections may

be reduced by control of thrips and other orchard insects and

by fungicidal sprays. One or two preharvest applications of fungicides in combination with a postharvest spray or dip gives better

results than either one alone. Frequent pickings to prevent fruit

from becoming overmature reduce severity of surface spotting.

(See SIf, 52, 5Jf, 68, 69, 101, 102, 175, 199, 2U5, 275.)

Aspergillus Black-Mold Rot

Aspergillus niger v. Tiegh.

Occurrence, symptoms, and effects

Black-mold rot of figs, often erroneously called **smut/' can be

found in figs on the tree, in the drying yard, and in dried, packed

figs as well It has been reported on figs from Georgia and California and on imported figs. It is more common on the white

varieties Calimyrna and Adriatic than on the black Mission or

white Kadota. It is one of the three chief causes of spoilage in

fresh figs.

The disease on fresh figs is characterized by a dirty-white to

slightly pink color of the skin and pulp of affected fruits and a

firm to finally a cheesy consistency of the pulp. A mass of white

mycelium develops within the fig. Eventually cavities are formed,

which become lined with the black spore masses of the fungus.

Spores may also be produced on the surface (pi. 12, D), Infection

varies greatly in severity. A severe infection gives fruit a dark

translucent appearance by which it is easily identified. A light

infection may produce merely dark or yellowish spots in the pulp,

with no spores. Fruit in this condition shows no signs of the

disease on the outside, is difficult to eliminate during the packing

process, and consequently may sometimes reach the market. Badly

"smutted*' figs, when squeezed, give off from the eye a black

cloud of fungus spores.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 65

Causal factors

Black-mold rot is caused by the fungus Aspergillus niger. The

same species causes a fruit rot of citrus, the black-mold rot of

onions, an internal rot of pomegranates, and a decay of the fruit

and fruit stems of grapes. The fungus is widely distributed in

nature and is common on the soil surface and on vegetable debris.

It also can live over from one season to the next on the small

twigs of fig trees. Spores are carried through the eye of the

fruit to the interior by fruit flies and other insects. In fully

mature or shriveled figs, the sugar content of the pulp is so high

the fungus cannot grow.

Control measures

Most of the infection takes place while figs are still on the

tree. More takes place if fruit falls to the ground. Careful handling

to reduce injuries and prevent contamination, as well as fungicidal dips to kill spores on fruit surfaces, reduce postharvest infections. Refrigeration at 31° to 32° F. holds decay somewhat

in check, but figs can not generally be held for more than 10 to

14 days.

(See 52, 53, 54, 1A8, 175, 196, 199, 27U, 276, 278.)

Blue-Mold Rot

Pénicillium sp.

Blue-mold rot, caused by Pénicillium sp., is sometimes found

on fresh figs on the market. Its development is relatively slow,

and the afliected tissues are only slightly softened. The disease

is readily recognized by the blue-green color of the fungus growth.

(See 52, 5k, 175.)

Cladospormm Spot

Cladosporium herbarum Lk. ex Fr.

Cladosporiiim herbarum causes occasional spotting of figs. The

spots appear first as dark olive-green specks that are particularly

noticeable on lightskinned varieties. As they enlarge, they become

slightly depressed and finally turn to a yellowish-olive color.
66 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

Cladosporium spot starts from a surface mold or '"smudge"

on either immature or mature fruit. As fruit approaches maturity,

a spot rot develops, largely caused by the Alternaría fungus. (See

Alternarla Spot.) While both Cladosporium and Alternaría are

present in the surface mold, the Alternaría predominates, Cladosporium does not appear to be involved in the active decay of

the fruit. However, cladosporium smudge can develop into spots,

chiefly on overripe figs, and cause minor losses of fresh figs.

Methods of control are the same as those recommended for

alternarla spot (p. 63).

(See 3^, 52, 68, 69, 101, 102, 175, 199.)

Endosepsis (Soft Rot)

Fusarium moniliforme Sheldon

Occurrence, Symptoms, and effects

This internal rot of fig is important in several fig-producing

areas of the world, but in the United States endosepsis is largely

restricted to California. In this State endosepsis is one of the

three major causes of mold spoilage.

Symptoms of endosepsis in edible figs are not always visible

externally, for the decay progresses from the cavity of the fig

outward. Sometimes the disease affects only the pulp, which

often becomes slightly watery and separates easily from the

meat. When the skin is affected, it takes on a watersoaked appearance in indefinite areas around the eye. These areas gradually assume a pink or purplish coloration. The flesh and pulp

inside are yellowish brown, disintegrated, soft and watery, and

may or may not have an offensive odor. In many cases the affected

figs have a putrid, somewhat bitter taste, and an odor suggestive

of spoiled tomatoes. Frequently the outside of a diseased fig

appears sound.

Causal factors

Endosepsis is caused by the fungus Fusarium moniliforme.

The spores are carried from infected caprifigs by the fig wasp,

Blastophaga psenes, during pollination. There are two general

kinds of figs, those varieties that require pollination (caprification) by the fig wasp, and varieties that are self-fertilizing.

Although the fig wasp requires the caprifigs for survival, it will

visit the self-fertilizing varieties as well and spread the fungus.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 67

The fungus grows in both the caprifigs and the self-fertilizing

varieties, but causes most decay in the latter.

Control measures

Nothing can be done after harvest to control development of

this disease in infected figs. Control has to take place in the field.

In the caprifig-growing regions of the United States, laws regulate

the growing of caprifigs.

(See 12, U, 52, 175.)

Gray-Mold Rot

Botrytis cinérea Pers. ex Fr.

Botrytis cinérea sometimes causes considerable loss of figs on

the market. The fig tissues soften, some juice leaks, and a growth

of gray fluffy or velvety mycelium spreads over the surface (pL

12, E), The disease occurs chiefly on overripe fruit.

Prompt refrigeration at 40° to 45° F. after harvest greatly

retards, although it does not entirely prevent, growth of the

fungus.

(See Si, 52.)

Soft Rot or Watery Soft Rot

Rhizopus nigricans Ehr.; Mucor sp.

Rots caused by Rhizopm nigricans and Mucor sp. have been

found occasionally on fresh figs on the market, although these

rots usually attack figs while they are still on the tree. The

trouble is favored by damp, rainy weather in the orchard and

by high temperature and high humidity in transit or in the

market. Fruit in very early stages of infection appears healthy

and is often picked along with the healthy fruit. During transit

or in the market this infected fruit becomes soft and leaky. The

skin and flesh of the fig turn brown, the affected area becomes

covered with a coarse, grayish mycelium, and black fruiting

bodies develop. Soft, overripe fruit is particularly susceptible

to these diseases. Figs that are picked at proper maturity, carefully handled, promptly cooled to 50° F. or lower, and kept cool

will not be seriously affected with Rhizopus or Mucor watery

or soft rots.

(See 52, 54, 64, 175, 199, 245.)
68 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

Souring

Various yeasts and bacteria

Occurrence, symploms, and effects

Souring is a disease or condition of figs that has been reported

from most fig-growing areas. In the United States it is especially

troublesome in large commercial fig orchards in California. It is

a destructive fermentation of the fruit which, if not controlled,

can cause the loss of nearly the entire crop. While mainly a

disease of fruit on the tree, it can escape detection in lightly

infected fruit, and the disease can spread during marketing.

In souring the pulp changes color from pink to colorless and

subsequently becomes watery. A pink liquid exudes from the eye,

dropping on leaves or jelling at the eye. The skin may become

watersoaked and soft, with gas bubbles inside the pulp. The pulp

disintegrates and smells strongly of alcohol. In many instances

the pulp is covered by a white scum. Figs then shrivel and dry

up. Fig souring is primarily an alcoholic fermentation, but subsequent changes by action of microorganisms on the alcohol produce acetic acid, which is readily discerned by its pungent, strong

odor.

Causal factors

Souring can be caused by several yeasts and acetic acid bacteria

carried into figs by insects, especially vinegar flies (Drosophila).

Two of the yeasts disseminated by drosophila have been identified

as Hanseniaspora and Torulopsis.

Control measures

Control of souring requires control of drosophila. In harvested

figs, spread of souring is restricted by discarding all sour and

endoseptic figs.

(See 42, 52, 54, US, 175, 197, 198, 245, 276,)

Splitting

Splitting or cracking at the eye end of the fig sometimes causes

heavy losses in the orchard and is occasionally found on the

market. The cracks may be mere crevices at the side of the eye

or may be so deep that the affected fig is practically split in

half.
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 69

Split figs attract vinegar flies (Drosophila), dried-fruit beetles,

and other insects which spread the fungi, yeasts, and bacteria

causing souring and other rots and decays.

Spherical or oblate figs apparently have a greater tendency to

split than elongated or pyriform figs. Also, figs from some districts split worse than the same varieties from other districts.

Splitting in the orchard appears to be associated with damp or

cool weather and a turgid condition of the fruit. It is probable

that package pressure and careless handling may increase splitting in transit and on the market.

(See 52, 2Jf5,)

Sunburn

Sunburn consists of dead, hard, tan-to-dark-brown bands about

14 of an inch wide, encircling the eye, or of similar blotches or

spots y% to % of an inch across, on the side of the fruit. Sunburn is not important on the market except as a blemish, although occasionally some molds become established on these dead

tissues. Control of sunburn is a field problem. Adequate irrigation

seems to reduce sunburn. Figs from vigorous trees have less

sunburn than figs from trees with low vitality.

(See 2Jf5.)

LYCHEES

Browning

Occurrence, symptoms, and effects

Browning is a physiological condition affecting the shell or

pericarp of the lychee fruit after harvest. It is associated with

the desiccation of fruit on exposure to dry air. On rough-fruited

varieties, such as Brewster (the major commercial variety in

Florida), browning starts at the tips of the tubercles, the horny

outgrowths of the shell, within several days after harvest under

favorable conditions. The discoloration progresses until brown

spots are easily discernible on the bright-red shell. Under severe

conditions or prolonged exposure, the spots enlarge and coalesce

until the surface is completely brown (pi. 13, A).

Browning results from desiccation at room temperature. The

flavor of browned fruit may or may not be adversely affected.

Off-flavors are most often associated with decay and fermenta-
70 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

tion by various yeasts that produce no typical external symptoms,

but browning may well be accompanied by ofF-flavors due to

yeast growth in the flesh. However, fruit browned at lower temperatures is not off-flavored until after an extended holding

period.

Control measures

Browning, desiccation, and yeast decay of lychees may be

best prevented or delayed by packaging the the fruit in polyethylene bags or other closed containers and storing at 35° F.

for up to 5 weeks. For storage periods of less than 2 weeks, a

temperature of 45"" plus polyethylene packaging is satisfactory.

No chemical control has been devised for extending the storage

life of lychees.

(See 5, kS, h^, 107, 157, 210,)

MANGOS

Anthracnose

Colletotrichum gloeosporioides Penz.

Occurrence^ symptoms, and effects

Anthracnose, also known as *'black spot'' or **ripe rot,'* is the

most important disease of mangos in regions where the fruit is

grown commercially. In the field it develops on all tender parts

of the tree and is especially severe on the flowers, young fruit,

and leaves. It causes flowers and young fruit to drop.

The fruit is susceptible to infection from blossoming time until

about half grown. Most of the decay on mature fruit develops

from latent infection when the fruit was small. These incipient

infections, which may be pinpoint in size on the growing fruit,

develop into large coalescing black spots as the fruits soften

at maturity (pi. 10, F), These spots frequently appear near the

stem as very small brown areas that enlarge rapidly and become

black. Often the entire surface of the fruit is covered by the

coalescing of the spots. The affected areas usually crack and

sink slightly. The decay is confined to the skin of the fruit,

except in the later stages when it may penetrate deeply and rot

the fruit either on the tree or after it has been harvested. Surface tearstaining or russeting may result from spores being
MARKET DISEASES OP CITRUS, OTHER SUBTROPICAL FRUITS 71

washed down upon the fruit from an infected twig or flower stalk.

These areas usually develop into rots as the fruit ripens.

Except in severe cases or during the late stages of decay, the

fruit is not greatly damaged and can be used after removing

the surface decay. However, the lesions detract markedly from

the appearance of the fruit. Ripe mangos, free from obvious anthracnose symptoms, are often difficult to find on the market.

Causal factors

The fungus (Colletotrichum gloeosporioides) causing anthracnose is the same one that causes anthracnose of avocado, citrus,

and papaya. On the mango tree it sporulates on the dead twigs

and leaves, from which the spores of the fungus wash onto the

susceptible parts of the tree. Rainy weather is an important

factor in spreading this fungus during bloom and early fruit

development.

Control measures

Fairly good control can be obtained in the grove with a rigid

spray schedule using copper, captan, and other organic fungicides.

Control of the postharvest rot of the fruit can best be attained

by hot-water treatment (ISO"" F. for 5 min.) at harvest time

before the fruit begins to soften. Since the fungus establishes

itself in the skin early, fungicidal washes applied to the fruit at

picking time are of no value.

(See 103, 106, 158, 195, 208, 211, 212, 222, 227, 2U7, 252.)

Chilling Injury

Mangos are harvested, packed, and shipped when the fruit is

mature but still green in color and firm. They are consumed after

they have ripened, which involves a loss of green color, softening

of the flesh, and development of a desirable flavor. Before ripening they are susceptible to chilling injuries when held at temperatures below 50° F. Chilling injury is manifested primarily as a

graying scald-like discoloration of the skin, often accompanied by

pitting, uneven softening, and poor development of color and

flavor (pi. 10, H), These symptoms usually appear while the fruit

is stored at unfavorably low temperatures. Under marginal conditions, the symptoms do not develop until the fruit is allowed to

ripen at higher temperatures. Fully ripened fruit is not as susceptible to the chilling injury as immature fruit.
72 AGRICULTURE HANDBOOK 398, U.S. DEPT. OP AGRICULTURE

Control measures

Chilling injuries of mangos can be avoided by using fully

mature fruit and storing at recommended temperatures. Most

varieties of fully mature unripened mangos can be stored successfully at temperatures of 50° to 55° F. for 3 weeks. For ripening, temperatures of 70 "" to 75° develop the most desirable color

and flavor. When fully ripened, the fruit can be held for several

weeks at temperatures of 35° to 40° without adverse effects.

(Seef, 15, 44, 106, 157,277.)

Stem-End Rot

Diplodia natalensis P. Evans

Occurrence, symptoms, and efiPecls

Stem-end rot of mango fruit frequently causes losses during

transit and storage. Diplodia natalensis, which causes stem-end

rot of citrus and other subtropical fruits, is usually associated

with this decay in Florida, but Phomopsis citri and other fungi

have been known to cause a stem-end rot. Factors that contribute

to the development of stem-end decay include the harvesting of

immature fruit and storage in poorly ventilated rooms at temperatures much above the 55° F. optimum storage temperature. The

decay usually starts at the stem end, although it may begin after

injuries at other locations on the fruit. The rot develops rapidly

at room temperature and involves the whole fruit within several

days after the initial stages of decay. The skin turns light brown

to almost black, forming a soft watery rot that has a sour fermented odor (pi. 10, G),

Control measures

Direct methods for control of stem-end rot of mango have not

been developed. However, the spray program and postharvest

heat treatment used for anthracnose control is beneficial in reducing stem-end rot (See control of anthracnose, p. 71.)

(See 106, 158, 222, 227.)
MÂEKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 73

PAPAYAS

Anthracnose

Colletotrichum gloeosporioides (Penz.) Sacc,

Anthracnose is the most important and widespread decay of

papayas on the market. It also affects the leaf petioles, flowers,

and young fruit in the ñeld. Lesions on the mature papaya usually appear first near the stem. They occur as saucerlike depressions, i^ inch or larger in diameter, in which the skin at

first is normal appearing or slightly deeper in color. The spots

develop rapidly and may coalesce to cover the entire fruit before

it is fully ripe (pL 13, B). As they enlarge, the lesions become

brown-to-black in the centers and are often covered with a scaly

wax composed of dried latex. The decayed area is shallow, fairly

firm, and may be readily lifted from the surrounding healthy

flesh. Under moist conditions, pink spore masses are produced

in the older or center part of the lesion.

Cause and control

The causal fungus, Colletotrichtim gloeosporioides, also causes

anthracnose of citrus fruits, avocado, and mango. Papaya fruits

may be infected at any stage in their development, but are particularly susceptible as they approach maturity. However, most

of the lesions do not become visible until the fruit begins to

soften.

The disease may be controlled in the field by fungicidal sprays.

Control of the postharvest decay of the fruit can best be attained by hot-water treatment or moist hot-air pasteurization at

harvest time before the fruit begins to soften. Application of

currently approved fungicides after harvest is of little or no

value.

(See 6, 9, U, 187, 208, 253.)
74 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

Stem-End Rot

Diplodia natalensis P. Evans, and other fungi

Stem-end rot of papayas frequently causes losses during transit

and storage. The rot usually starts at the stem end, although it

may follow injuries incurred shortly before harvest at other

locations on the fruit. The infection develops rapidly at room

temperature and will rot the entire fruit within a week after

the first stages appear. The skin of the affected area may remain

yellow like the remainder of the sound ripened fruit, or turn a

light brown forming a soft watery rot that has a sour fermented

odor (pi. 13, C).

Cau§e and control

Diplodia natalensis, which causes stem-end rot of citrus, mangos, and other subtropical fruits, is usually associated with this

decay in Florida, but Phomopsis citri and Dothiorella gregarea

have been known to cause a decay with similar symptoms. Direct

methods of control have not been developed. However, storage at

temperatures of 45° to 50° F. will retard decay development,

and the postharvest heat treatment used for anthracnose control

reduces stem-end rot.

(See ^5^).

PINEAPPLES

Black Rot

Ceratocystis paradoxa (Dade) C. Moreau

Occurrence, symptoms, and effects

Black rot (sometimes called ''water blister," *'soft rot," or

"water rot") of pineapples is found in all commercial pineapplegrowing regions of the world. The fungus causing this rot attacks all parts of the growing plant, but it is rarely seen on

pineapple fruit in the field unless the fruit is allowed to ripen

fully. On ripening fruit shipped long distances to market, it

frequently assumes major importance. All commercial varieties

are susceptible, but the Red Spanish variety is considered more

resistant than the Cayenne variety.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 75

Black rot may originate at the base of the fruit, through the

cut stem, or at the side of the fruit through injuries received

during packing and handling. In side infections, rotting progresses much more slowly than in basal infections. The decay

in the fruit is characterized by a slightly brown watersoaked

appearance of the affected tissues. It soon becomes very soft and

almost liquid, with the skin of the fruit forming a brittle shell

The fungus grows rapidly through the water-conducting strands

in the core of the fruit, producing no external evidence of decay

except for slight softening at the site of infection. In later stages

the fruit becomes so completely disintegrated that it yields to the

slightest pressure. On broken or otherwise exposed surfaces, decayed tissues become covered with a black crust composed of

macrospores of the fungus. These also form in the decayed tissues

near the core of the fruit, turning it black (pi. 13, D), Under

warm conditions the vascular strands in the fruit are not disintegrated as rapidly as the remaining tissue, thus giving a

decided stringiness to the decayed portion. A sweetish odor of

fermentation accompanies the decay.

Causal factors

Black rot is caused by the fungus Ceratocystis paradoxa, better

known by the name of its imperfect stage, Thielaviopsis paradoxa

(De Seyn.) Hoehn. This fungus is widely distributed in tropical

and subtropical countries, where it causes important diseases

of pineapple, sugarcane, bananas, and other plants. The organism

lives and sporulates freely on dead plant parts in the pineapple

fields. Thus abundant infective material is present at harvesttime. When the fruit is removed from the stalk, the cut allows

easy entry for the fungus. It also may enter the fruit through

insect punctures or through injuries received during harvesting,

packing, and marketing. Much of the rot on the side follows

packing bruises that could have been prevented by proper handling

and sizing of fruit. Although it is probable that the fungus cannot penetrate the uninjured surface of the fruit, very small,

invisible cracks between the eyes may allow infection if they

come in contact with decayed tissue from a neighboring fruit.

More than 48 hours elapse between the time of infection and the

appearance of symptoms.

Moisture conditions in the field at harvest are very important

in decay development. High percentages of decay in a shipment

usually mean that the fruit was harvested either during or im-
76 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

mediately after a prolonged rainy period. The relation between

moisture and the decay is so marked that in some sections it

is called "water rot"

The fungus develops in the fruit very rapidly at temperatures

between 70^ and 90'' F., but becomes almost quiescent below 50''.

It develops more rapidly in ripe than in green fruit. At room

temperature, a ripe fruit may become entirely decayed in 3 or

4 days.

Control measures

Fruit for the fresh market should be cut and not snapped from

the plant. Care should be taken in handling and packing to avoid

bruising the fruit. Proper sizing insures a tight pack without

side-bruising the fruit, thus avoiding resultant side decay. Sunburned, damaged fruit, or fruit with an excessive number of

growth cracks should be excluded from fresh fruit shipments.

The packing of wet fruit should be avoided, and the packed cases

or cartons should be kept dry.

Protecting the fruit against fungus invasion will almost completely control black rot starting at the stem end. Fungicides and

treatments that have been used include: Immersing the whole

fruit and crown in a 10-percent o-phenylphenate solution; dipping

the lower half of fruit in a 1-percent sodium salicylanilide solution ; spraying or painting the cut end of the fruit with 214 percent salicylic or benzoic acid in 80-percent alcohol solution or a

10-percent bensoic acid-kaolin mixture (1:4); or dusting 25-

percent benzoic acid dust on the cut surface. Dipping or spraying

treatments are usually more effective than dusting and are easier

to perform. For maximum protection, fruit should be treated

within 2 hours after cutting.

Black rot will not develop in fruit refrigerated at 45° F. For

fruit in the ripe and half-ripe stages of maturity, this temperature is satisfactory during transit. Green fruit at this temperature may fail to develop good flavor and may retain part of the

green color in the skin, so that shipping and storage is generally

at 45"" to 55°, usually with ventilation.

(See 3, 8, 29, 30, 50, 128, 160, 162, 168, 191, 208, 283.)
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 77

Brown Rot

Erwinia ananas Serrano^ Fusarium moniliforme Sheldon,

Pénicillium funiculosum Thorn, and Pseudomonas

ananas Serrano

Occurrence, symptoms, and effects

Pineapples on the market sometimes show brown rotten spots,

from which Pénicillium sp., Fusarium sp., or bacteria can be

isolated. This is commonly called brown rot in United States

markets, but in pineapple-producing areas it is variously referred

to as "fruitlet core rot," "fruitlet brown rot," ''fruitlet black

rot," "ripe fruit rot," "marbled fruit," "bacterial fruitlet rot,"

"exogenous brown discoloration," "black rot," and "black spot."

Disease symptoms vary somewhat, depending upon whether fungi,

bacteria, or both, cause the disorder. It is often hard to differentiate between the rots by appearance only.

Brown rot can rarely be detected from the outside of the fruit,

though underdeveloped fruitlets and uneven coloring or ripening

may be an indication. Some badly affected eyes may become brown

and sunken as the fruit ripens. Internal symptoms consist of

small light-to-dark brown, moist, firm, decayed, mottled areas at

the center of the fruitlet or eye. Sometimes only the style or

central part of the fruitlet is affected, although frequently the

entire fruitlet is involved. In later stages the decay may progress

to the core of the fruit and involve all of the tissues immediately

surrounding the floral cavity (pi. 13, E). It rarely spreads from

one fruitlet to another. The decay may develop in fruit during

transit and marketing as well as in ripe or mature fruit in the

field.

The decay also occurs as a thin, tan, dry layer lining deep

cracks between fruitlets. These cracks, which are usually accompanied by a gummy exúdate, are apparently caused by growing

conditions in the field. Before the fruit is picked, the cracks are

contaminated with the organisms, which then initiate the shallow

decay and produce the typically colored sporulation, pink or

white with Fusarium, and blue-green with Pénicillium, Where

bacteria cause the rot, the affected fruitlets are filled with masses
78 AGRICULTURE HANDBOOK 398, U.S. DBPT. OF AGRICULTURE

of bacteria. Diseased tissue cultured on potato-dextrose agar

yields yellow (Erwinia emanas) or white (Pseudomonas ananas)

bacteria.

Causal factors

This disease seems to develop very rapidly, but only during

ripening. The fungi and bacteria most frequently associated with

the decay are common saprophytes on rotting vegetation in the

field. They grow on the decaying floral remnants of pineapple in

the cavities under the eyes but can enter the flesh of the fruit only

through injuries or breaks in the hard lining of the cavity. Such

breaks or injuries may be caused by growth cracks or the feeding of certain insects, such as mealybugs and mites. Apparently

the organisms can gain entrance into the eye and work down the

floral parts into the center of the fruitlet at any stage of fruit

development, but flesh decay is fastest in ripe or nearly ripe

fruit. The disease is especially severe when a dry season is followed by wet weather. Growth cracks and mealybugs are then

especially common.

Control measures

Although the disease is fairly prevalent, especially in pineapples from the warmer, humid areas, and most of the organisms

causing it are known, no effective means of controlling this kind

of fruit-rot damage have been developed.

Fruits of low acidity are more susceptible to bacterial infections. Cultural practices that result in high acidity may be effective in reducing bacterial decay.

(See 16, 50, 65, 66, 109, 126, 128, lk9, 152, 190, 191, 192, 208,

2Si, 235, 286, 287, 2^8, 262, 265.)

Physiological Breakdown

Occurrence, symptoms, and efFects

Physiological or internal breakdown of pineapple fruits, often

called ^'waterlogging" or "juicy pineapples,'' is characterized by

a firm light-brown watersoaking of the flesh of the fruitlets,

beginning near their attachment to the core in a region an inch

or two above the base of the fruit. The watersoaking progresses

upward, and may eventually involve all of the fruitlet except the
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 79

ovary and a layer about i/4 inch deep below the skin. Only in

advanced stages do the surface of the fruit and the core become

discolored (pi. 13, F). These fruit may change from a normal

yellow to a dull hue. Sometimes the leaves are rather loose in

their sockets and some can be plucked out easily, or even the

entire crown may be lifted from the fruit. Surface molds may

increase rapidly on severely affected fruit. Most fruits, however,

have no external symptoms of the disorder. Severe cases of

physiological breakdown are frequently discovered in pineapples

that appear normal and attractive from the exterior. The disorder

is not a form of overripeness.

Causal factors

Microorganisms do not cause physiological injury in pineapples. The most common or usual cause of physiological breakdown is exposure of the fruits to relatively low temperatures.

Storing or shipping pineapples at 32° to 40"" F. is especially harmful (pi. 13, G). The critical temperatures below which injury

occurs are between 41° and 45^, depending on the particular lot

of fruit. Pineapples unloaded and held in cold weather in northern

ports have been observed to develop physiological injury. This

disorder is relatively common in pineapples ripening in cool

winter months but rare in summer fruit unless they are subjected

to cool temperatures after harvest. After the fruit is removed

from storage, physiological damage becomes more severe with

time.

Conditions other than low temperature may start the physiological breakdown. The disorder has been observed in imported

fruits that have not been subjected to low temperatures during

transit. A somewhat similar if not identical disorder may be induced by heavily waxing mature fruits or by holding them in

airtight containers.

(See 55, 8U, 85, 157, 178, 208, 271, 273.)

POMEGRANATES

Pomegranates are remarkable for their keeping quality and

are exceptionally free from diseases, as compared with other

fruit. They may be picked before fully ripe to ripen during storage. The fruit are easily kept 4 to 7 months in excellent condition at 32^ to 38° F. and 80 to 85 percent humidity. The rind may

dry and harden during storage in dry air, but the interior remains good and even improves.
80 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

Gray-Mold Rot

Botrytis cinérea Perg. ex Fr.

Pomegranates on the market are occasionally affected with a

light-brown, firm decay starting at the calyx. The decayed skin is

tough and leathery, but the inner part of the fruit is dark and

disintegrated. Under moist conditions, a sparse mycelium of a

dirty-gray color appears on the decayed area. At various points in

the mycelium, the typical tan-gray spore-bearing tufts develop.

Control measures for the disease have not been reported. It is

probable, however, that the development of the rot in transit and

storage can be greatly retarded if the temperature is kept below

45° F. However, the Botrytis fungus can develop at low temperatures and grow slowly even at 32°.

(See 179, 208.)

Heart Rot

Aspergillus niger y* Tiegh., Aspergillus ë^p.^ and Alternaría

sp.

Heart rot, sometimes called **fruit rot," is found only occasionally in pomegranates on the market, but in some years it is

so prevalent in the orchard that heavy culling in the packinghouse is necessary. The decay has been found in fruit from the

various producing districts of southwestern United States. It

rarely appears on the surface of the fruit, but the skin color of

affected fruits is slightly abnormal, so that experienced graders

can eliminate most of it from the pack. Diseased fruits when

opened are found to contain a mass of blackened arils (pi. 12, F)

(the pulp-bearing seeds) and usually a threadlike black line of

decay extending from the calyx into the interior of the fruit.

Typical symptoms of the decay are produced by species of

Aspergillus and a species of Alternaría. The only control measure

that can be suggested is the gathering and destroying of all

affected fruits found in the orchard.

(See 111, 112, 16i, 176, 208, 259, 260.)

Internal Breakdown

In some seasons, pomegranates from certain areas may occasionally be affected with a peculiar condition of the arils (the

pulp-bearing seeds). The arils have a lighter color than is normal,
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 81

are rather flat and unsatisfactory in taste, and exhibit a streaked

appearance. Many delicate white lines can be seen radiating in all

directions from the seed to the outer wall of the aril. There are

no external symptoms of this deterioration, and no organism has

been identified that causes it. It is a physiological disorder.

(See 111, 112, 179.)

Pénicillium or Blue-Mold Rot

Pénicillium expansum Lk. ex Thorn and other Pénicillium

species

Pénicillium rot is found occasionally on pomegranates. It starts

at splits, cracks, or insect wounds and forms pockets of blue- or

green-spored fungus colonies (pL 12, G). Aspergillus, Alteriiaria,

or Botrytis often occur in the same wounds with the Pénicillium,

in which case one or another of these fungi often overgrow the

Pénicillium and predominate.

(See 179, 259, 260.)

Splitting and Cracking

During ripening, the pomegranate is very susceptible to splitting and cracking (pi. 12, H). This is a common malady of pomegranate fruit, and is a natural characteristic, similar to splitting

in figs and oranges. The exact cause of pomegranate splitting is

not known, but a common idea is that it is due to sudden fluctuations in the moisture content of soil and air, due to irrigations,

dry winds, etc. Splitting is always worse in fruit that is allowed

to become overmature on the trees. To avoid splitting, fruit

should be picked just before becoming mature. The pomegranates

then ripen very well during storage. Split or cracked fruit

quickly develops Botrytis, Pénicillium, Aspergillus, or Alternaría

rots, especially when stored in warm moist areas.

(See 35, 111, 112, 232.)

Sunscald or Sunburn

Pomegranates at almost any stage after blossoming hang with

the blossom end down and thus are exposed at the stem end to

injury by the sun. This appears as brown, slightly russeted, very

tough, leathery areas of the rind. Sometimes they are on only one

side of the fruit but may extend entirely around it. The injury

does not lead to decay and is of importance only as a blemish.

(See 111, 112, 208.)
82 AGRICULTURE HANDBOOK 398, U.S. DEPT. OF AGRICULTURE

LITERATURE CITED

(1) ANONYMOUS.

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(2)

(3)

(4)

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(6) »-

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(7) »

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(14) — CROWDY, S. H., and MCKEE, R. E.

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MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRVITB 83

(17) BARTHOLOMEW, E. T.

1926. ALTERNARíA ROT OF LEMONS. Calif. Agr. Expt. Sta. Bui. 408,

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(18)

1937. ENDOXEROSIS, OR INTERNAL DECLINE, OP LEMON FRUIT. Univ.

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(20) BlALE, J. B.

1940. EFFECT OP EMANATIONS FROM SEVERAL SPECIES OF FUNGI ON

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(21)

(22)

1940. EFFECT OP VAPORS FROM MOLDY FRUITS ON COLORING AND RESPIRATION OF LEMONS. Calif. Citrog. 25: 186, 212.

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(23) ——— and SHEPHERD, A. D.

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1966. MAINTAINING MARKET QUALITY OF FRESH LYCHEES DURING

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1968. INTERFRUITLET CORKING OF PINEAPPLE FRUIT, A NEW DISEASE

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1934. AVOCADO DISEASES IN CALIFORNIA. Calif. Agr. Expt. Sta.

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1967. HOT WATER TREATMENTS FOR CONTROL OF PENICILLIUM DIGITATUM GREEN MOLD OF EUREKA LEMONS. Phytopathology

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1942. THE HANDLING AND STORAGE OF AUSTRALIAN ORANGES,

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1965. SERIOUS DISEASES OF CITRUS FOREIGN TO FLORIDA. Fla. Dept.

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Press Bui. 47, 12 pp.

(279) WINSTON, J. R.

1921. TEAR-STAIN OF CITRUS FRUITS. U.S. Dept. Agr. Dept. Bui.

924, 12 pp., illus.

(280) ~

1923. CITRUS SCAB. ITS CAUSE AND CONTROL, U.S. Dept. Agr.

Dept. Bui. 1118, 39 pp.
1935. REDUCING DECAY IN CITRUS FRUITS WITH BORAX. U.S. Dept.

Agr. Tech. Bui. 488, 32 pp.

1938. ALGAL FRUIT SPOT OF ORANGE. Phytopathology 28 (4) : 283-

286.

MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 101

(281)

1933. SOME FACTORS INFLUENCING DECAY IN FLORIDA CITRUS FRUITS.

Fla. state Hort. Soc. Proc. 46: 82-84.

(282)

(283)

(284) ^

1950, HARVESTING AND HANDLING CITRUS FRUITS IN THE GULF STATES.

U.S. Dept. Agr. Farmers Bui. 1763, 67 pp., illus.

(285) and BOWMAN, J. J.

1923. COMMERCIAL CONTROL OF CITRUS MELANOSE. U.S. Dept. Agr.

Dept. Cir. 259, 8 pp.

(286) WOLF, F. A.

1926. THE PERFECT STAGE OF THE FUNGUS WHICH CAUSES MELANOSE

OF CITRUS, Jour. Agr. Res. 33 (7) : 621-625.

(287) WOLFE, H. S,, TOY, L. R., and STAHL, A. L.

1946. AVOCADO PRODUCTION IN FLORIDA. Fla. Agr. Expt. Sta. Bui.

129, 107 pp.

(288) YAMADA, S., and YAMAMOTO, S.

1962. STUDIES ON THE EPIDEMIOLOGY OF CITRUS MELANOSE AND STEMEND ROT. Nati. Hort. Sta. Tokai-Kinki Bui. 6: 108-116.

(289) ZENTMYER, G. A.

1946, DISEASES OF THE AVOCADO. Calif. Avocado Soc. Yearbook 31:

79-83.

(290) —

(291)

1951. AVOCADO DISEASES. Calif. Avocado Soc. Yearbook 36: 97-101.

1953. DISEASES OF THE AVOCADO. Plant Diseases, U.S. Dept. Agr.

Yearbook, 1953: 875-881.

(292) —

1961. AVOCADO DISEASES IN THE AMERICAS. Ceiba 9 (2) : 61-79.

(293) PAULUS, A. 0., GUSTAFSON, C. D., and ot^rs.

1965. AVOCADO DISEASES. Calif. Agr. Expt. Sta. Cir. 534, 11 pp.

MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 103

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 1

DECAYS AND ROTS OF CITRUS FRUITS

A, Alternarla black rot at stem end of orange; B, alternarla side rot of

orange; C, alternarla black rot of navel orange; D, advanced stage of alternarla rot; E, alternarla rot of lemon; F, anthracnose of grapefruit; G,

anthracnose of tangerine following degreening; H, aspergillus rot of

tangerine.
104 AGRICULTURE HANDBOOK 398, U.S. DEFT. OF AGRICULTURE

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 2

DECAY AND ROTS OP CITRUS FRUITS

A, Green-mold rot showing stages of development; B, blue-mold rot of

orange; C, botrytis rot of orange; D, brown rot of tangerine; E, brown

rot of lemon; F, cottony rot of orange; G, contact cottony rot of lemons;

H, fusarium rot of orange.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 105

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 3

DECAYS AND ROTS OF CITRUS FRUITS

A, Sour rot of orange (early and late stage) ; B, diplodia stem-end rot of

orange; C, diplodia stem-end rot of grapefruit; D, phomopsis stem-end rot

of orange; E, phomopsis stem-end rot of grapefruit; F, trichoderma rot of

lemon (early) ; G, trichoderma rot of lemon (later) ; H, black pit of orange.
106 AGRICULTURE HANDBOOK 398, U.S. DEFT. OF AGRICULTURE

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 4

ORCHARD DISORDERS AFFECTING MARKET QUALITY

A, Melanose (common) ; B, melanose (mudcake) ; C, melanose (tear stain) ;

D, septoria spot of orange; E, scab of Temple orange; F, exanthema of

orange; G, creasing of orange; H, creasing (peeled to show voids in

albedo).
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 107

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 5

H

ORCHARD DISORDERS AFFECTING MARKET QUALITY

A, Grasshopper or katydid damage to orange; B, scale injury preventing

normal degreening of orange; C, scale injury preventing normal color development of Temple orange; D, early season rust-mite injury of orange;

E, late season rust-mite injury of grapefruit; F, thrip injury of orange;

G, leaf scarring of orange; H, thorn injury of orange.
108 AGRICULTURE HANDBOOK 398, U.S. DEFT. OF AGRICULTURE

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 6

PHYSIOLOGICAL

â!#

DISEASES OP CITRUS FRUITS

A, Aging of grapefruit; B, aging of oranges; C, peteca of California lemons;

D, pitting of freshly harvested Pineapple orange; E, low O2 injury of

orange; F, pitting of orange following storage in N2; G, stylar-end breakdown of lime; H, granulation of navel orange compared with normal.
MARKET DISEASES OF CITRUS, OTFIER SUBTROPICAL FRUITS 109

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 7

FREEZING AND CHILLING INJURIES OP CITRUS FRUITS

A, Hesperidin crystals on segment walls, resulting from freezing injury of

tángelo; B, freeze damage of grapefruit (internal drying, external pitting) ; C, freeze damage of orange (internal buckling and drying, external

pitting) ; D, phomopsis side rot of grapefruit following storage pitting;

E, storage pitting of grapefruit; F, storage pitting and brown staining of

oranges following chilling; G, pitting of limes following chilling injury;

H, albedo browning of lemons.
lio AGRICULTURE HANDBOOK 398, U.S. DEFT. OF AGRICULTURE

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 8

DISORDERS FOLLOWING CHILLING AND OTHER INJURIES

A, Oil-gland darkening of grapefruit; B, brown staining of Temple orange;

C, membranous stain of lemon; D, hot-water damage to grapefruit; E,

SOPP injury to grapefruit; F, chemical injury due to spray residue on

grapefruit; G, chemical injury (dry fertilizer) to grapefruit prior to

harvest; H, sand bruising of grapefruit due to sand on bottom of field

boxes.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 111

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 9

X

MISCELLANEOUS DISORDERS OF CITRUS FRUITS

A, Rind-oil spotting of Marrs Early orange; B, rind-oil spotting following

insect injury of orange; C, bruising of navel orange followed by color-add

treatment; D, brush burn of orange; E, zebra skin of tangerines due to

handling immature fruit following rainy periods (note poor color of

affected fruit); P, sunburn injury of tángelo; G, pufRness of tangerine;

H, water spot of navel orange.
112 AGRICULTURE HANDBOOK 398, U.S. DEFT. OF AGRICULTURE

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 10

DISEASES AND DISORDERS OF AVOCADO AND MANGO

A, Anthracnose of avocado; B, scab of avocado; C, cercospora spot of avocado; D, diplodia stem-end rot of avocado; E, chilling injury of avocado;

F, anthracnose of mango; G, diplodia stem-end rot of mango; H, chilling

injury of mango.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 113

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 11

DISEASES AND DISORDERS OP BANANA

A, Anthracnose of banana; B, botryodiplodia fruit rot of banana; C, pitting

of bananas; D, thielaviopsis rots of bananas; E, chilhng injury of banana

peel; F, internal chilling injury of banana.
114 AGRICULTURE HANDBOOK o98, U.S. DEFT. OF AGRICULTURE

Agriculture Handbook 398, U.S. Dept, of Agriculture PLATE 12

DISEASES AND DISORDERS OF FIG AND POMEGRANATE

A, Alternarla rot of fig (early infection) ; B, alternarla rot of fig (severe

infection) ; C, alternarla rot of fig (around eye) ; D, aspergillus black rot

of fig; E, botrytis gray-mold rot of fig; P, heart rot of pomegranate; G,

blue-mold rot of pomegranate; H, splitting of ripe pomegranate.
MARKET DISEASES OF CITRUS, OTHER SUBTROPICAL FRUITS 115

Agriculture Handbook 398, U.S. Dept. of Agriculture PLATE 13

0®©

DISEASES AND DISORDERS OF LYCHEE, PAPAYA, AND PINEAPPLE

A, Physiological browning of lychees; B, anthracnose of papaya; C, stem-end

rot of papaya; D, black rot of pineapple; E, brown rot of pineapple; P,

physiological breakdown of pineapple (successive slices from base of

fruit) ; G, chilling injury of pineapple at 35° P.

ft- GPO : 1971 O—409-004
PRECAUTIONS

Pesticides used improperly can be injurious to man^ animals,

and plants. Follow the directions and heed all precautions on the

labels.

Store pesticides in original containers under lock and key—out

of the reach of children and animals—and away from food and

feed.

Apply pesticides so that they do not endanger humans, livestock, crops, beneficial insects, fish, and wildlife. Do not apply

pesticides when there is danger of drift, when honey bees or other

pollinating insects are visiting plants^ or in ways that may contaminate water or leave illegal residues.

Avoid prolonged inhalation of pesticide sprays or dusts; wear

protective clothing and equipment if specified on the container.

If your hands become contaminated with a pesticide^ do not

eat or drink until you have washed. In case a pesticide is swallowed or gets in the eyes, follow the first aid treatment given on

the label, and get prompt medical attention. If a pesticide is

spilled on your skin or clothing, remiove clothing immxcdiately and

wash skin thoroughly.

Do not clean-spray equipment or dump excess spray material

near ponds^ streams, or wells. Because it is difficult to remove all

traces of herbicides from equipment, do not use the same equipment for insecticides or fungicides that you use for herbicides.

Dispose of empty pesticide containers promptly. Have them

buried at a sanitary land-fill dump, or crush and bury them in a

level, isolated place,

NOTE : Some States have restrictions on the use of certain

pesticides. Check your State and local regulations.

Trade names are used in this publication solely to provide

specific information. Mention of a trade name does not constitute a warranty of the product by the U.S. Department of

Agriculture or an endorsement by the Department over other

products not mentioned.