al^ tí-^iLÍHo '^Snculture Handbook No. 240

Controlling

INSECTS and

DISEASES of

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U.S. DEPARTMENT

OF AGRICULTURE
CONTENTS

Page

Insects of the pecan 2

Hickory shuckworm 2

Pecan nut casebearer 3

Pecan weevil 5

Aphids 8

Plant bugs 11

Pecan leaf casebearer 12

Spittlebug 14

Fall webworm 14

Walnut caterpillar 15

Twig girdler 16

Pecan phylloxera 17

Obscure scale 18

Mites 19

Pecan bud moth 20

Flatheaded apple tree borer 20

May beetles 22

Red-shouldered shot-hole borer.... 22

Curculios 23

Diseases of the pecan 24

Scab 24

Rosette 27

Downy spot 29

Vein spot 31

Page

Disease of the Pecan—Continued

Leaf blotch 32

Brown leaf spot 33

Liver spot 34

Crown gall 35

Bunch disease 36

Wood rot 38

Cotton root rot 39

Powdery mildew 39

Nurser/ blight 39

Pink mold 40

Lichens 41

Spanish-moss 42

Injury caused by climatic conditions.. 43

Winter injury 43

Sunscald 43

Lightning injury 44

Insecticides and fungicides 45

Precautions 45

Insecticides 46

Fungicides 47

Spray machines 48

Spray schedule for control of pecan

insects and diseases 49

'-^^

By MAX R. OSBUEN and WILLIAM C. PIEECE, entomologists,

and A. M. PHIIXIPS, formerly entomologist. Entomology Researcb Division, and

JOHN R. COLE, plant pathologist, and GEOEGE L. BAENES,

formerly plant pathologist, Crops Research Division,

Agricultural Research Service

This handbook replaces the material

formerly contained in U.S. Department

of Agriculture Farmers' Bulletin 1829,

"Insects and Diseases of the Pecan and

Their Control".

Washington, D.C. Issued May 1963

For sale by the Superintendent of Documents, U.a. Oovenunent Printing Office

Washington 25, D.C. - Price 25 cents
Controlling INSECTS

and DISEASES of

' thePEPM

Many kinds of insects and disease organisms attack pecan trees

and threaten the crop of nuts.

They do it in several ways. Some

insects damage the bark or heartwood. Others tunnel or girdle the

branches and cause them to break

off. Still others attack the buds,

leaves, or nuts. Some kinds of pests

are present throughout the growing

season; others are present for

shorter periods, either early or late.

Disease organisms—principally

fungi—that infect the pecan usually attack the growing tissues, including leaves, shoots, and nuts. In

severly affected orchards, trees may

be so badly injured that most of

the leaves are shed or practically

all the nuts are lost. Disease

spreads most rapidly early in the

growing season during periods of

damp weather.

The growth of the pecan industry

has brought new problems in controlling pests. The pests increase

rapidly because large acreages of

pecan orchards provide an abundant supply of the food they prefer. Species that were not commonly present have transferred to

pecans from hickories and other

plants.

The damage caused by several of

the major insects and diseases tends

to be particularly severe in planted

and topworked orchards comprised

of large numbers of trees of a few

varieties; in such orchards the damage is more severe than it is in native or seedling groves in which

every tree is different.

The commercial pecan grower

must control harmful insects and

diseases to produce profitable crops

of nuts. First, the insects and diseases affecting the trees must be

identified; then effective control

measures must be used. It is often

a waste of time and money to apply

control measures to trees of poor

varieties or to those that are in a

low state of vigor because of lack of

care, inadequate soil fertility, or

crowding.

Certain cultural practices will

promote tree vigor, stimulate fruiting, and help to minimize the damage caused by some pests.

1
INSECTS OF THE PECAN

HICKORY SHUCKWORM

The hickory shuckworm is the

most destructive insect that infests

the pecan. It is generaly distributed throughout the Pecan Belt,

west to and including Texas.

Larvae of this insect attack the

nuts from about the first of June

until harvest. They tunnel in and

destroy the interior of the nuts (fig.

1) until the shells harden late in

August. Nuts infested early fall to

the ground. At least half the crop

may be lost to shuckworms, especially when there is a light set.

Usually, it is difficult to see the

entrance holes made by shuckworm

larvae except under magnification.

Their presence, however, may often

be detected by a white stain around

the point of entrance on freshly

dropped nuts.

.yr?'

BN-^629

Figure 1.—Damage caused by larvae of the hickory shuckworm: A, Larvae in immature nuts;

3, larvae mining the shuck of a nearly mature nut; C, nuts showing shell stains and adhering

parts of damaged shucks.

After shells have hardened, the

larvae tunnel in the shucks and prevent the kernels from developing

properly. Nuts heavily infested by

shuckworms are likely to be poorly

filled and to mature later than those

free from this pest. Injured portions of the shucks sometimes stick

to the nuts and interfere with processing. Shells often are badly

stained.

Shuckworms also feed on hickory

nuts, causing injury similar to that

done to the pecan. Early in the

spring, they may feed in phylloxera

galls.

These insects pass the w-inter as

ñül-gi-own larvae in the shucks on
the ground. The larvae are I/3 to

% inch long, creamy to dirty white,

and have brownish heads. They

transform into pupae, and the

pupae into dark, inconspicuous

moths.

In southern Georgia, the moths

begin to appear the middle of February. Most moths of this generation emerge in April, but small numbers continue to appear well into

summer. The spring development

of the insect coincides with that of

the nuts of native hickory, which

set 2 to 3 weeks earlier than those

of the pecan. Only the late-emerging moths of the spring brood lay

their eggs on the foliage and small

nuts of the pecan.

Few pecan nuts become infested

with shuckworms before June.

Starting in June, the sliuckworm

population increases rapidly with

successive generations, of which

there are four or five in the latitude

of southern Georgia.

Control

No entirely satisfactory control

of the shuckworm is known. However, 2 pounds of 25-percent EPN

or Guthion wettable powder in each

100 gallons of water, applied as a

spray, is fairly effective in preventing late season damage after shell

hardening, and often results in improved quality nuts. Make three

applications, the first about August

10 to 15 and the second and third

at 2-week intervals. See Precautions, page 45.

If you have only a few trees or

are not equipped to spray, you may

reduce infestation by gathering and

destroying the pecan shucks at

harvest.

PECAN NUT CASEBEARER

The pecan nut casebearer causes

damage throughout the Pecan Belt.

Losses varj' considerably from year

to year and with the size of the crop.

A light to moderate infestation in

a heavy set of nuts may merely provide a desirable thinning, but if it

occurs in a light crop, most or all

of the nuts may be destroyed.

The casebearer passes the Avinter

as a partly grown lan^a in a small,

tightly woven cocoon (fig. 2), sometimes called a hibernaculum, which

usually is found where a bud joins

tlie stem. The larvae become active in spring about the time the

buds begin to open. They feed for

a short time on the buds, and then

bore into the young, tender shoots.

Full-grown larvae are about onehalf inch long ; they have olive-gray

to jade-green bodies and yello^vish

brown heads. They transform into

pupae either in the tumieled shoots

or in cocoons that tliey attach to

other parts of the tree.

The rather inconspicuous dark

gray moths usually emerge in May.

They appear in largest numbers

about the time the nuts are setting.

They lay greenish white eggs on the

blossom end of the nuts. Usually

only one egg is laid in a cluster of

nuts.

Most of the damage by this insect

is caused in May and June by the

first-generation larvae. Newly

hatched larvae usually descend

from the nut clusters to feed on the

buds just below. After a few days

they return to tlie clusters and attack the newly set nuts. Infested

nuts are held together by silken

threads (fig. 3). They are easily
Figure 2.—Winter cocoon of the pecan nut casebearer at the base of a bud.

recognized by the mass of frass cast one to all the nuts in a cluster. A

out by the larvae. In the course of larva matures and pupates in one

its development, a single larva of of the last nuts it attacks in a cluster

this generation may destroy from (fig. 4).

BN—36-tO

Figure 3.—Cluster of nuts infested by the pecan

nut casebearer.

BN-3643

Figure 4.—Larva iA) and pupa (B) of the pecan

nut casebearer within small nuts.

Moths of the second generation

appear in late June and early JulyLarvae of this generation also attack the nuts, but the loss is less be-
cause the nuts are larger, and an

individual larva requires only one

or two nuts for its development.

Larvae of later generations feed

mostly on the surfaces of the shucks

and to some extent on the leaves;

they do little damage. Larvae of

the last generation in the season

construct cocoons about the buds;

in these, they overwinter. Three

generations of this insect are most

common, although four generations

have occurred in Texas.

Control

Usually, no control is needed

when the nut crop is normal or

above normal, and not more than

about 3 percent of the shoots of the

previous year are infested with

overwintering larvae. Under all

other circumstances, and especially

if there is a history of serious infestation, an insecticide program

should be undertaken.

You can make an effective spray

by mixing in each 100 gallons of

water one of the following wettable

powders: 2 or 3 pounds of 50-percent DDT; or 2 pounds of 25-percent EPN, 15-percent parathion, or

25-percent Guthion ; or 3 pounds of

25-percent malathion. Or, you can

mix 1% pints of a 25-percent parathion emulsifiable concentrate in

100 gallons of water.

If you use a dust, apply a 2-percent parathion dust at the rate of 50

pounds per acre, or a 10-percent

malathion dust at the rate of 40

pounds per acre. See Precautions,

page 45.

A single application of any of

these sprays or dusts will give adequate control of the nut casebearer

in most orchards. If the infestation

is severe, make two applications

about a week apart. Make the first

application before many first-generation larvae enter the nuts, between about April 20 and May 25.

Start applications when eggs are

readily found on the tips of the

young nuts. The eggs are very

small but large enough to be seen

without magnification.

In the latitude of Albany, Ga.,

the usual date to start applications

is about May 15 ; in southern Texas,

the last of April or the first of May ;

and in central and northern Texas,

from May 5 to 25. The timing of

the first application may be based

on nut development and catkin

shed. In northern Florida apply

insecticide about the time the tips

of the nuts turn brown, and in other

areas about the time catkin shed is

complete on such varieties as

Schley, Stuart, and Mahan. Applications by airplane should be made

shortly after the first larvae enter

nuts.

PECAN WEEVIL

The pecan weevil (fig. 5) is a

light-brown or grayish beetle about

one-half inch long; it has a long

beak. This insect infests the nuts

and causes serious loss in pecan production in the Piedmont areas of the

Southeastern States. In most years

it causes some losses in other pecanproducing States, particularly in

Louisiana, Texas, and Oklahoma.

The weevils do not ordinarily

move far from the tree under which

they emerge from the soil, provided

there is a crop of nuts on that tree.

Consequently, certain trees may be

heavily infested year after year;
BN-3635

Figure 5.—Pecan weevils on Schley pecans.

other trees of the same variety close

by may have few, if any, infested

nuts. Usually tlie trees most heavily infested in an orchard are those

growing in low areas or adjacent to

hickory trees.

Pecan varieties differ widely in

their susceptibility to attack. Early-maturing varieties such as Stuart, Schley, Mahan, and Moneymaker are most commonly infested.

Late-maturing varieties such as

Success, Teche, Mobile, and Van

Deman usually are not attacked unless the crop on the early maturing

varieties is very light or was destroyed before the insect finished

feeding and egg laying. Practically all kinds of hickory nuts are

attacked.

Pecan weevil damage may be one

of two types, depending on the stage

of nut development at the time attack occurs. The first type of damage is caused by attack before the

nut shells become hard ; this damage

causes all punctured nuts to drop.

Female weevils usually begin depositing eggs in nuts after the kernels begin to form. Attack during

this period causes the second type of

damage ; it leads to destruction of

the interior of the nut and to adherence of the shuck to the shell.

Nuts injured by the second type of

damage (fig. 6) contain grubs that

destroy the kernels, or they contain

holes about one-eighth inch in diameter through which mature grubs

may escape after destroying the

kernels.

The first type of damage often

passes unnoticed. However, it may

destroy the entire crop if weevils

are abundant and the crop is light.

Such damage may be heavy even

when a large crop is attacked. The

second type of damage is generally

noticeable at harvesttime, and may

affect practically the entire crop in

seasons when large numbers of

weevils are present.

The time when adult weevils

emerge from the soil varies with the

season and the locality. In central

Georgia they usually emerge between August 1 and September 1,

and in central Texas after periods

of heavy rainfall in August or early

in September.

Egg laying begins about the last

week in August : the actual date de-
B

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Figure 6.—A, Nearly mature grubs of the pecan weevil within Stuart pecan; B, grub emerging

through hole in nut; C, nut that has hole through which mature grub may escape.

pends upon the time of hardening of the kernels and the presence

of weevils. Females drill holes

through the shucks and shells, and

place an average of three eggs

apiece in separate pockets within

the kernels.

Grubs emerge from the nuts between the last of September and the

last of December, and sometimes

later. They enter the soil to a depth

of 4 to 12 inches and construct

earthen cells, where they remain 1

or 2 years. They pupate between

the first part of September and the

middle of October and transform

into adults in about 3 weeks. These

adults remain in the soil until the

following summer. The complete

life cycle requires from 2 to 3 years.

Control

DDT is the most effective insecticide yet found for the protection of

pecans from weevils. Use 6 pounds

of a 50-percent DDT wettable

powder in each 100 gallons of water

or fungicide. Make two applications, the first when at least six

weevils can be jarred onto a sheet

spread on the ground beneath any

tree known to have been infested in

previous seasons, and the second 10

to 14 days later.

The first application may be

needed by the first week in August

in Georgia, Alabama, Mississippi,

and Louisiana; it may be needed

the first or second week in August

in South and North Carolina, and

after the first heavy rain late in

August or early in September in

Texas.

When spraying for pecan-scab

control, delay the last seasonal application of the fungicide until you

make the first application of DDT

for weevil control, since recommended fungicides can be used with

DDT.

Toxaphene will also control the

pecan weevil. Mites and aphids do

not increase as rapidly after its use

as they do after the use of DDT.

Use 6 pounds of a 40-percent toxaphene wettable powder or 21/2 pints

963409 0—63-
of an emulsifiable concentrate containing 1 pound of toxaphene per

pint or the equivalent of other toxaphene formulations to prepare 100

gallons of spray. Toxaphene

should not be used with Bordeaux

mixture but can be used with zineb.

EPN will control light and medium infestations of the pecan weevil. Mix 2 pounds of a 25-percent

EPX wettable powder in each 100

gallons of water. Make three applications beginning xVugust 10 to 15

as recommended for the hickory

shuckworm. EPN can be used with

fungicides recommended for scab

control.

To determine the time for the

first insecticide application, start

jarring the trees about a week before you expect the application may

be needed. See Precautions, paire

45.

If you have only a few pecan trees

or are not prepared to spray, you

can reduce weevil injury about 50

percent by lightly jarring the limbs

and gathering the weevils. You

should begin jarring for control at

the time indicated for determining

spray dates: repeat weekly untü

about September 15. To determine

tlie presence of weevils, you need

to jar only a few of the trees known

t-o be the most heavily infested year

after year. If the weather is dry,

few weevils will be taken and fewer

jarrings will be needed until rains

soften the ground.

To collect the weevils, place harvesting sheets under the trees and

jar each limb lightly two or three

rimes to dislodge the insects. Use a

padded pole or a pole with a metal

liook Ijolted to one end. It may be

necessary to climb high trees and

jar each limb with the foot. Pick

up the weevils from the sheets and

kill them by placing them in a

bucket or can containing kerosene.

The dislodged weevils will remain

quiet on the sheets long enough to

be picked up.

APHIOS

Several species of aphids infest

pecan trees ; the most destructive is

t he black pecan aphid.

Practically all important pecan

varieties are affected by aphids,

especially in the South and Southeast, and at times in other parts

of the Pecan Belt. The presence of

Bordeaux mixture or DDT on the

leaves sometimes seems to cause the

aphids to increase in numbers.

The first sign of injury on the

leaflets is a bright yellow area where

the insect has fed (fig. 7). This

yellow area eventually turns brown.

As the season advances and the

aphids increase in numbers, the entire leaf may drop prematurely.

Aphids feed on both sides of the

leaflets and prefer the shaded, inner parts of the tree. As injured

leaflets drop, the aphids migrate toward the outside of the tree. Premature dropping of many leaves

cuts off the supply of plant food

(fig. 8) ; it prevents the proper fillin,<r of the nuts and reduces the

following year's crop.

The black pecan aphid passes the

winter in the egg stage in crevices

in the bark. Late in March the

eggs hatch into wingless aphids,

which move out to the opening buds

and leaves where they feed until

fully grown.

8
Figure 7.—Pecan leaf injured by the black

pecan aphid. Note aphids on injured

areas.

At first, the aphids are light

green, but after feeding a short

time they become dark green to almost black. Wlien fully grown,

they give birth to living young.

Some aphids develop wings and fly

to other parts of the same tree or to

other trees.

About 15 successive generations

occur through the season. Each

mature aphid produces about 60

young. Under favorable conditions a very heavy infestation may

develop from a low-population

level within a 3- or 4-week period.

Examine orchards weekly from

July through September to detect

such increases before they reach an

advanced stage. With the approach of cold weather, the insects

lay eggs for the overwintering generation.

Three species of yellow aphids—

the black-margined aphid, and two

related species of Monellia—often

occur in large numbers on the undersides of the leaves. The extent

of the injury they cause is unknown, but they excrete large quantities of honeydew, which makes

the leaves sticky and supports the

growth of a sooty mold that interferes with the functioning of the

leaves. Development and seasonal

histories of these aphids are similar

to those of the black pecan aphid.

Control

Tlie black pecan aphid and other

aphids that may be present can be

controlled with parathion or malathion applied in dilute, semiconcentrated, or concentrated sprays.

They can be controlled also with

parathion dusts.

In dilute sprays, add 1 to I14

pounds of 15-percent parathion or

2 pounds of 25-percent malathion

wettable powder to each 100 gallons

of water; add these wettable powders either alone or in combination

with fungicides and, if needed to

control mites, wettable sulfur.

In semiconcentrated or concentrated sprays, use sufficient material

to apply 1 pound parathion or 114

pounds malathion per acre.

A dust containing either 1 percent of parathion or 1 percent of
Figure 8.—Pecan trees defoliated by the black pecan aphid.

parathion plus 40 percent of sulfur,

applied at the rate of 50 pounds

per acre, has also been effective.

In airplane applications, good

results against aphids have been obtained in Louisiana by applying to

each acre of pecan trees either 1

pound of parathion (% gallon of

25-percent emulsiñable concentrate) in 5 gallons of water, or 1.25

pound of malathion ( 1 quart of 57-

percent emulsifiable concentrate)

in 4 gallons of water. In Greorgia,

airplane applications of 1 pint of

40-percent TEPP emulsifiable concentrate in 5 gallons of water per

acre of pecan trees have been effective. Airplane applications of

parathion or malathion require a

following period of about 48 hours

without heavy rainfall to give best

results.

The black pecan aphid can be

controlled also by applying a spray

made by mixing one of the following with each 100 gallons of water :

1 pint of demeton emulsifiable concentrate (2 pounds of demeton per

gallon of concentrate) ; 11/2 to 2

pounds of 25-percent EPN wettable powder; 1% to 2 pomids of

Guthion wettable powder; or onehalf pint of Trithion emulsifiable

concentrate (4 pounds of Trithion

per gallon of concentrate). See

Precautions, page 45.

The black pecan aphid varies so

much in its abundance that no set

spray schedule can be given for its

control. For best results begin

treatments as soon as yellow spots

appear on the foliage. In some seasons this may be as early as May;

10
in other seasons, treatment may not

be necessary.

A single treatment may hold the

aphid population in check for 3

weeks or more. Be sure to cover

both surfaces of the leaves with

the spray. Give special attention to

the inner parts of the trees, where

the aphids are usually most numerous early in the season. It is useless to apply an insecticide after

many of the leaves have dropped

and the aphid population is large.

If sufficient mites are present to

require treatment, apply an insecticide such a parathion, which will

control both mites and aphids at

the same time. Use malathion in

situations or locations where it is

unsafe to use the other recommended insecticides.

If other species of aphids become

abundant, control can be effected

with the treatments recommended

for the black pecan aphid.

PLANT BUGS

The southern green stink bug

(fig. 9, 4), the leaf-footed bug (fig.

9, 5), and similar bugs sometimes

cause black pit and kernel spot of

pecan nuts.

Black pit is indicated by a

darkening of the insides of the immature nuts, which is followed by

premature dropping. The pecan

weevil and the hickory shuck^vorm

cause a somewhat similar condition.

Kernel spot (fig. 10) consists of

brown spots from y^g to ^/ig inch

in diameter forming a pithy, porous

area. The injui-y cannot be detected until the nuts have been

shelled. The spots are bitter, but

this bitter taste does not extend to

the rest of the kernel. Nuts will

TC-2774 BN-3e3(»

Figure 9.—>4, Southern green stink bug; 6, leaffooted bug. Enlarged.

drop if the bugs attack them before

the shells liave become hard (black

pit), but after the shells have

hardened the nuts do not drop and

spots on the kernels are formed.

The severity of black pit and kernel spot varies with the abundance

of plant bugs in an orchard, and

the abundance of bugs depends on

the native plants or cover crops

present on which they breed.

11
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BN-3624

Figure 10.—Kernel spots on ridges and edges

of the kernels of Schley .-lecans.

The various plant bugs that cause

black pit and kernel spot have somewhat similar life habits. The

southern green stink bug, which

usually is the most prevalent, is

shield shaped and about one-half

inch long. It spends the winter in

trash or similar shelter in or near

the orchard. In spring it lays eggs

in clusters underneath the leaves of

weeds, cover crops, or other lowgrowing plants. These plants ser\-e

as food for the bugs until they become fully grown. There may be

as many as four generations of these

l>ugs in a year. Pecan nuts are attacked only by the mature bugs,

which fly to the trees from plants

on which they developed.

Control

The use of proper cover crops and

orchard sanitation are the best

methods of controlling plant bugs

that cause black pit and kernel

spot. Do not plant cowpeas, soybeans, or Crotalaria striata as summer cover crops in or near the orchard. Till the soil in the orchard

two or three times during the summer to destroy wild hosts such as

beggarweed, thi.stle, jimsonweed,

and maypop. If the orchard is in

permanent pasture or being grazed,

and plant-bug hosts are present,

mow several times during the summer. For winter cover crops use

legumes such as hairy vetch or reseeding crimson clover.

No effective insecticide treatment

to control these plant bugs is known.

PECAN LEAF CASEBEARER

The pecan leaf casebearer occurs

most commonly in northern Florida

and the southern parts of Georgia,

Alabama, Mississippi, Louisiana,

and Texas.

The insects pass the winter as

immature larvae in small cocoons

about the buds, similar to cocoons

constructed by the nut casebearer.

In spring, the small larvae leave

their winter cocoons and attack the

unfolding buds and foliage (fig.

11). Wlien the infestation is heavy,

they may keep pecan trees in a

semidefoliated condition for 3 or 4

weeks.

On reaching maturity, the larvae are slightly over one-half inch

long, dark green, and have shiny,

dark-brownish heads; they transform to pupae within a case they

construct about themselves while

feeding.

The small, grayish brown moths

appear from about the middle of

May until the first part of August.

The moths deposit their eggs on the

lower surfaces of the leaves along a

vein or near the junction of a vein

12
TC-3333

Figure 11.—Young pecan buds injured by larvae

of the pecan leaf casebearer.

with the midrib. Young larvae that

hatch from these eggs feed sparingly on the undersides of the leaves

(fig. 12) from the middle of May

until November, rarely attaining a

length of more than one-sixteenth

inch by fall. Late in August or

early in September the immature

larvae begin to leave their cases on

the under surfaces of the leaves and

migrate to the buds, where they construct their winter cocoons. The insect passes through only one generation a year.

Confrol

Control the leaf casebearer by

spraying the trees either when the

buds begin to open or in the summer

from late in June until the middle

TC-3866

Figure 12.—Feeding cases and injury to lower

surface of pecan leaf by newly hatched

larvae of the pecan leaf casebearer. Enlarged.

of August. Use 2 pounds of a 15-

percent parathion wettable powder

or 3 pounds of a 25-percent malathion wettable powder in each 100

gallons of water. If you are following a spray schedule to control scab,

add the insecticide to the second

prepollination application if two

prepollination applications are recommended, or to the last fungicide

application in July.

Airplane applications of a dust or

spray will control the insects when

they resume feeding in spring.

Apply a 5-percent malathion dust

at the rate of 40 pounds per acre;

13
or apply a mixture containing 5 gallons of a 5-pound-per-gallon malathion emulsifiable concentrate in

each. 50 gallons of water. See Precautions, page 45.

SPITTLEBUG

The spittlebug is common on pecan in northern Florida, along the

gulf coast, and in parts of Kentucky and Illinois. It may attack

pecan trees also wherever they occur

along the Atlantic coast from Massachusetts to Florida and westward

to Kansas.

Tlie young bugs, usually several

together, produce masses of white,

frothlike material about the buds,

tender shoots, or nut clusters (fig.

13) in spring, beginning shortly

after the nuts are set, and again in

midsummer. They suck the juices

from the parts they attack. Heavy

BN-3625

Figure 1 3.—Pecan nuf cluster showing spittlelike substance produced by the spittlebug.

infestations kill the terminal shoots

which results in a smaller crop.

Adults are pale brown, have a

reddish tinge, and are about threeeighths inch long. They are commonly called froghoppers because

of their resemblance to frogs. They

deposit eggs in small slits ia the

bark twigs of the previous season's

growth that are one-half inch or

smaller in diameter; usually they

deposit several eggs to a slit.

The insect overwinters in the egg

stage.

Control

Light infestations of spittlebugs

do not cause sufficient damage to

make control necessary. If spittlebugs become abundant, they may be

controlled with one application of

parathion or toxaphene about the

middle of May. Use either 2 pounds

of 15-percent parathion wettable

powder or 21/^ pounds of 40-percent

toxaphene wettable powder in each

100 gallons of water.

If you are using a scab-control

schedule, add the insecticide to 100

gallons of fungicide in the second

prepollination application, but do

not use toxaphene with Bordeaux

mixture. See Precautions, page 45.

FALL WEBWORM

Fall webworms are caterpillars

that feed in colonies and make unsightly webs on pecan trees during

summer and fall. Usually all the

members of a colony hatch from a

mass of eggs deposited on a leaf

by a single moth. The caterpillars

feed on both surfaces of the leaves,

and enlarge the web as they need

more leaves.

14
When fully grown, the caterpillars are a little more than one inch

long and are covered with long

white and black hairs. They spin

flimsy cocoons beneath loose debris

on or just below the surface of the

soil. Usually there are two broods

a year. The second brood, usually

the larger, feeds during fall.

Control

Fall webworms can be killed with

a spray application containing

DDT, parathion, EPN, Guthion

or malathion. (Use a wettable

powder.) Mix 2 pounds of 50-percent DDT, 15-percent parathion, 25-

percent EPN or Guthion, or 3

pounds of 25-percent malathion

wettable powder in each 100 gallons

of water. Control is needed only

when the insects are very mmierous

in an orchard, and should be undertaken when the caterpillars are

small. See Precautions, page 45.

If there are not many webworms,

it may be practical to remove the

webs from the trees before the caterpillars have left them—preferably

before they have done much feeding. Use a long-handled tree

pruner or a bamboo pole with a

hook at the end.

WALNUT CATERPILLAR

Walnut caterpillars feed in

groups ; they often eat all the leaves

on small trees or on certain limbs

of large trees (figs. 14 and 15).

They do not form webs on the

leaves.

In the South, the first generation

appears in June and July, and the

second generation in late August

and September. As they grow, the

BN-3e22

Figure 14.—Walnut caterpillars clustered on

trunk of pecan tree.

caterpillars molt, or shed their

skins, several times. In preparation for molting, they go down to

a large limb or to the trunk of the

tree and form a compact mass.

After shedding their skins, they go

back toward the ends of the

branches and resume their feeding.

Control

The same spray treatments recommended for the fall webworm

will control this insect. Caterpillars clustered on the trunk or limbs

of a tree (fig. 14) may be destroyed

by crushing or burning.

863409 O—63- 15
Figure 1 5.—Colony of walnut caferpillars on a pecan shoot.

TWIG GIRDLER

The twig girdler often girdles the

twigs of pecan and other trees late

in summer and during fall (fig. 16).

The injured branch may break off

and drop to the ground, or it may

remain on the tree. This insect generally is present wherever pecans

are grown. It is especially abundant in orchards near timberland

where hickories and persimmons

abound.

Twig girdlers ai'e brown beetles

1/2 to % inch long. They lay eggs

in the twigs that they girdle, and

these eggs hatch into whitish, leg16

less grubs. The grubs make little

growth during the fall and winter

months, but in spring they grow

fast and tunnel in the twigs. They

complete their growth and transform into beetles during the latter

part of August. Usually, one year

is required for development of the

insect, although some individuals

do not complete development ointil

the second season.

Control

To reduce damage that might occur m following years, gather and

burn the severed branches late in

fall or in winter or early spring.
BN-3621

Figure 16.—Twig gtrdler girdling a pecan

branch.

when the eggs and grubs are in the

twigs. Gather all branches lodged

in the trees, those on the ground,

and those from infested nearby

trees such as hickory and persimmon.

Apply a spray to prevent damage

in orchards that have a history of

infestation. Use 4 pounds of a

50-percent parathion wettable

powder, or 2 pounds of a 25-percent

EPN or Guthion wettable powder

in each 100 gallons of water. Make

three applications at 2-week intervals, beginning when the first injured branches are noticed late in

August. See Precautions, page 45.

PECAN PHYLLOXERA

Swellings, or galls (fig. 17), occasionally appear on leaves, leafstalks, succulent shoots, or nuts of

the current season's growth. These

galls are caused by small insects

known as phylloxera, which are

closely related to aphids. One or

more species are found in almost

all sections of the Pecan Belt, but

Figure 17.—Galls of phylloxera on a pecan

twig.

17
only one species has been reported

as doing serious damage.

The attack of this insect causes

the shoots to become malformed,

weakened, and finally to die. Sometimes an entire limb may die.

Especially serious damage has been

reported from Arkansas, Louisiana,

Mississippi, Oklahoma, and Texas.

The insects pass the winter in

the egg stage in protected places on

the branches. The young appear in

spring about the time the buds unfold. An insect inserts its beak

into the new growth, and a gall

forms that soon envelops the insect.

The insect matures within the gall

and lays a large number of eggs.

The young insects that hatch from

these eggs develop into winged

forms. Usually late in May or

early in June, the gall splits open

and releases the insects.

Control

Spray the trees thoroughly with

BHC, lindane, or malathion during

the delayed dormant period; do

this before buds show 1 to 2 inches

of new growth and before the galls

appear. Use 21/2 pounds of BHC

containing 10-percent of the gamma isomer, or use 1% pounds of

25-percent lindane wettable powder, or use 3 pounds of 25-percent

malathion wettable powder in each

100 gallons of water.

Dinitro materials may be applied

only when the trees are dormant,

from late February until the buds

begin to swell. To each 100 gallons"

of water, add 3 quarts of 36-percent dinitro-o-sec-butylphenol liquid, or add a mixture containing 2

pounds of 40-percent dinitro-o-cyclohexylphenol powder plus a 2-

percent dormant oil emulsion. See

Precautions, page 45.

OBSCURE SCALE

The obscure scale is a serious pest

of pecans in Texas, Louisiana, Arkansas, and Mississippi. It also

occurs in other parts of the Pecan

Belt. Its body is covered with a

circular scalelike substance, usually

dark gray, similar to the color of

the bark, so that the insect is difficult to detect until it becomes abundant. It attacks the branches and

trunk of the tree. The bark of

heavily infested branches appears

roughened or scaly (fig. 18).

TC-9712

Figure 1 8.—Obscure scale on pecan twigEnlarged.

18
This scale insect sucks the sap

from plant tissues. The greatest

injury comes from the gradual killing of branches less than 3 inches

in diameter. Larger branches are

seldom killed, though they may

be so weakened that they will not

produce normal nuts. The slow,

progressive killing of infested

branches reduces the number of

fruiting shoots and weakens the

tree, making it subject to attack by

borers.

This insect has only one generation each year. The young, or

crawlers, are present from about

the middle of May until early in

August. Soon after they hatch, the

crawlers settle on the bark, insert

their beaks, and begin to form their

waxy scale coverings. They gradually increase in size and, except for

the adult males, do not move

around.

Control

Spray infested trees thoroughly

with a dormant-oil emulsion before

the buds begin to swell, preferably

in January or February. If the

trees are in a weakened condition,

use a spray material containing 2

percent of oil, but if they are vigorous, use one containing 3 percent

of oil. Weak, slow-growing trees

are more subject to oil injury than

are vigorous trees. Commercial

oil emulsions are made in different

strengths; dilute them to the desired strength according to directions on the containers.

MITES

Several species of mites attack

pecan trees throughout the Pecan

Belt. A heavy infestation causes

serious loss of foliage. The most

common and injurious mite is

known only by its scientific name,

Tetranychus hicoriae. It is pale

green, and so small that it is barely

visible without magnification. It

feeds principally on the undersides of the leaves, but may occasionally be found on the upper

sides.

Infested leaflets first show a slight

discoloration about the midrib,

where the mites usually start to

feed. Later the discoloration

spreads outward, and the leaflets

look as if they have been scorclied.

Fresh scorch injury appears as dark

brown or liver-colored blotches, and

old scorch injury as dead areas of

irregular size and pattern. Severely injured leaflets turn brown

and drop off. An infestation generally starts on the lower branches

of the pecan trees and spreads upward.

The life history and habits of

hicoriae have not been studied in

detail, but they seem to be similar

to tliose of the two-spotted spider

mite, a species that occurs on many

kinds of plants throughout the

United States. Injury has been observed in June, but seems to be most

severe during August, September

and early October. The mites develop most rapidly in hot, dry

weather. There are several generations each year.

Other species of mites sometimes

occur along with hicoriae or instead

of it, particularly in Louisiana and

Texas. One species, Eriophyes

caryae, rolls the edges of the leaflets, and others, Breviqjalpu.s spp..

19
feed along the veins on the undersides.

Control

Spray the trees with 2 pounds of

15-percent parathion wettable

powder, or its equivalent, in each

100 gallons of water, whenever a

mite infestation becomes evident

and before it has caused the foliage

to drop. Instead of parathion, you

may mix in each 100 gallons of

water one of the following: 1 pint

demeton emulsifiable concentrate (2

pounds of demeton per gallon) ; 2

pounds 25-percent EPN wettable

powder ; 2 pounds 25-percent Guthion wettable powder ; 2 pounds 18.5-

percent Kelthane wettable powder;

or 1 pint malathion emulsifiable

concentrate (5 pounds of malathion

per gallon).

If the infestation persists; make

a second application after about 10

days. In the western portion of the

Pecan Belt, where mites other than

hicori/ie are likely to occur, add 4

pounds of wettable sulfur to the

insecticide spray material. Treatments for mites can be combined

with those for aphids and disease

control, if the treatments are needed

at or near the same time. See Precautions, page 45.

PECAN BUD MOTH

The larvae of the pecan bud moth

often cause serious damage to pecan

nursery stock by feeding on and in

the terminal buds and foliage.

Also, the larvae occasionally defoliate large pecan trees, feed on the

tips of and bore into the young nuts

in spring, and infest the shucks in

fall.

The adult is a small gray moth ;

it has blackish brown patches on the

forewings and a wingspread of

about two-thirds inch. The insect

overwinters in the adult stage.

Overwintering moths start egg-laying about the time the buds begin

to open, and place their eggs on the

twigs near buds. Later, after the

foliage appears, they lay most of

the eggs on the upper surfaces of

the leaves. Larvae feed for about

25 days. When fully grown they

are yellowish green, have darkbrown heads and necks, and are

five-eighths inch long. There are

probably five or six generations

each year.

Control

Young nursery trees should be

kept in a strong, healthy condition

by proper cultivation and fertilization. Vigorously growing trees are

better able than slow growing ones

to withstand attacks of the pecan

bud moth.

Spray infested trees with 2

pounds of 50-percent DDT, or 15-

percent parathion wettable powder

in each 100 gallons of water; or

apply a 2-percent parathion dust

at the rate of 20 pounds per acre.

Airplane applications of parathion dust have given good control

on young nursery trees. Four or

five applications should be made at

intervals of 2 to 3 weeks, beginning

when damage is first observed.

Control is seldom necessary in bearing orchards. If bud-moth damage

is threatened, apply insecticide as

needed. See Precautions, page 45.

FLATHEADED APPLE TREE BORER

The adult flatheaded apple tree

borer (fig. 19) is present in pecan

20
orchards from spring to late fall.

It attacks pecan trees of nearly

every age wherever they are grown.

Injury is usually confined to trees

that have already been weakened

from some other cause, such as those

injured in cultivation, by cold,

drought, or sunscald, or retarded by

transplanting. Borers usually

work on the sunny side of a tree

trunk.

BN-3(

Figure 19 A natheaded apple-tree borer

feeding in wood of a tree.

Injury results from the tunneling

of the borers in the bark and sapwood of the trunk. Trees 2 inches

or less in diameter may be girdled

and killed, and larger trees may be

weakened. The presence of one

borer in a tree often leads to further attack. The insects disclose

their burrows by pushing frass

from the cracks in the bark. Injured spots can often be detected by

the darker color and slight depression of the bark.

Adult beetles are about one-half

inch long, flattened, and metallic in

appearance. They lay their eggs in

cracks in the bark, or in injured

places on the sunny parts of the

tree trunks. The larvae, or borers,

are readily recognized by their

large, flattened heads. The insect

passes winter in the borer stage and

pupates in spring. Development

from egg to adult usually requires

a year.

Control

The most effective way to prevent

injury by these borers is to maintain vigorous trees by following approved practices of cultivation,

fertilization, spraying, and conservation of soil moisture.

You can protect newly transplanted trees by wrapping the

trunks from the ground to the lower

limbs with newspaper, burlap, or

crepe paper of double thickness,

placing asphalt between the layers.

Wind the wrapping spirally or vertically, and hold it in place with a

light cord. Apply the wrapping

soon after the leaves appear in

spring and leave it in place as long

as it is serviceable, provided the

cord does not girdle the trees.

Wlien trees are infested, remove

the borers with a knife, cutting into

the bark and wood as little as possible. Hold the knife blade flat

against the tree and work along the

course of the burrow ; trim the edges

later. Removing the bark and frass

from the deeper part of the burrow

21
is believed to hasten healing of the

wound. To keep the wood from

drying- until the bark heals over,

paint the deeper parts with a pruning compound or with a mixture

of one part of creosote and three

parts of coal tar.

Examine young trees at least

once a year, preferably in March or

April before mature borers emerge.

If the infestation is heavy, examine

trees during summer for grubs overlooked.

MAY BEETLES

May beetles, or June bugs, sometimes defoliate pecan trees in

spring. Small trees surrounded by

uncultivated land are most subject

to injury. The beetles feed at

night ; in the daytime they lie hidden just beneath the surface of the

ground.

The adult beetles (fig. 20) are i/o

(o 3/4 inch long, robust, and usually

brown. They lay their eggs in the

ground, and the larvae, which are

white grubs, feed on the roots of

plants, particularly grasses. Larval

development requires 2 years or

more.

Figure 20.—May beetles.

Control

Since the grubs of May beetles

feed in the soil, especially in sod

land, they are seldom injurious in

well-cultivated orchards that are

some distance from uncultivated

land. Fields near orchards are a

source of infestation, but if the

soil is plowed once a year, the May

beetles are not likely to become

very numerous.

Beetles on small trees may be

shaken onto sheets on the ground at

night and destroyed. On both small

and large trees, control can be obtained by applying parathion,

Guthion, EPN, or malathion, when

the beetles are first noticed.

If infestation persists, two or

three spray applications may be

necessary. In each 100 gallons of

water, mix 2 pounds of 15-percent

parathion wettable powder or 2

pounds of 2.5-percent Guthion,

EPN or malathion wettable powder.

See Precautions, page 45.

RED-SHOULDERED SHOT-HOLE

BORER

The red-shouldered s h o t-hole

borer makes small exit holes in the

bark of pecan trees. These holes

give the trunk the appearance of

having been hit by shot (fig. 21).

The first signs of these borers in

a tree are light sawdust particles

coming from the holes. Injury

caused by severe drought or cold

weakens trees for borer attack.

Several similar insect species work

on weak trees; some of them feed

only on the bark and in the cambium region ; others go deep into the

heartwood.

22
TC-4522

figure 21.—Exit holes of adults of the redshouldered shot-hole borer.

Control

To control the borers, keep trees

in a healthy condition and as

far as possible reduce sources of

infestation, such as dead trees and

prunings. Application of a quickacting fertilizer often assists in restoring an individual tree if it is

not too severely weakened.

CURCULIOS

Two species of curculio that attack pecan are Gonotraclielu» peoanae and aratm; the latter is

know as the hickory shoot curculio.

They attack the imfolding buds and

shoots on pecan late in March and

in April in some areas of the Pecan

Belt. Severe infestations occur

most commonly on uncultivated

trees and in cultivated orchards adjacent to woodlands containing native pecan and hickory trees. Fifty

percent or more of the shoots may

become infested.

The larvae of pecanae tunnel in

the buds and tender shoots, and

when present in large numbers may

kill or weaken many nut-bearing

shoots. Larvae of the hickory

shoot curculio tunnel within the

shoots and leaf stems near the point

where the leaves are attached, causing premature loss of foliage and

weakening the shoots.

A third species, Conotrachelius

hicoriae, attacks immature pecan

nuts during late June, July, and

early August in some parts of Louisiana, Arkansas, and Mississippi.

The larvae tunnel in the nuts before the shells harden, and cause

them to drop. The injury is similar

to that caused by the shuckworm.

Damage appears to be light when

the trees set a good crop of nuts.

Control

BHC and lindane have given

fairly good control of pecanae.

Mix 4 pounds of BHC (10-percent

gamma), or 1% pounds of 25-percent lindane wettable powder in

each 100 gallons of water. Apply

when the buds show from 1^4 to 1

inch of green growth or when jarring of the trees indicates that

many adults are present. BHC has

also been partially effective against

aratus when applied shortly after

the leaves begin to unfold or separate from the tender shoots. No

tests have been conducted against

hicoriae. See Precautions, page 45.

663409 O—63- 23
DISEASES OF THE PECAN

The pecan is affected by fungus,

bacterial, and virus diseases and by

environmental disorders of various

kinds. Fungus diseases are caused

by small, usually microscopic,

plants. Bacterial diseases are

caused by one-celled microscopic

organisms. Virus diseases are

caused by submicroscopic agents,

the exact nature of which has not

yet been determined. In contrast,

the environmental disorders are

caused by conditions such as a deficiency of one or more mineral elements (resulting in nutritional diseases) , sudden changes in temperature, varying amounts of moisture,

or other adverse nutritional or climatic factors.

Fungus diseases are by far the

most numerous and widespread of

the diseases that attack the pecan.

For this reason they offer the most

difficult problems in control. Bacterial and virus diseases are of

much less importance. The environmental disorders may often be

of considerable importance in certain localities, but because they are

not infectious they are usually less

serious in their effects and less difficult to control.

SCAB

Scab, a fmigus disease, is very

destructive to the pecan, especially

in the Southeastern States and in

the southern part of the Gulf Coast

States. Its control is of major importance to the industry.

Scab attacks certain seedling

trees and those of most grafted varieties. Most of the older varieties

that have been planted extensively

are scabbing so badly that they produce poor-quality nuts or none at

all in certain areas of high rainfall

and high humidity. Even Stuart,

one of the oldest and most widely

planted varieties, is now severely

affected in some areas of Mississippi. Moneymaker, Teche, and Curtis, varieties formerly considered

immune, have now been found to be

susceptible to scab in some localities. Scab on Curtis is confined

mostly to young trees growing in

nurseries. Newer varieties that

have been less extensively planted,

such as Desirable, Farley and Elliott, appear to be liighly resistant.

Nevertheless, it seems probable that

all varieties and seedlings eventually will be found susceptible.

Scab fungus attacks the rapidly

growing tissues of leaves, shoots,

and nuts. Wlien leaves and shoots

stop growing they become somewhat resistant to infection, but the

nuts remain susceptible until shortly before they mature. Vigorously

growing trees of scab-susceptible

varieties are therefore more severely affected than are those in a low

state of vigor.

The greatest damage is done to

the nuts, the loss sometimes being

complete. On highly susceptible

varieties—such as Schley, Teche,

and most of the western varieties--

defoliation often results, especially

when frequent infections occur

from early spring into the summer.

The scab fungus overwinters in

the infected spots on old leaves and

shucks or on the shoots of the trees.

24
When weather conditions become

favorable in the spring, the fungus

becomes active and produces spores.

The spores are carried by water and

air movements to new leaves,

shoots, and nuts, where they may

cause further infections (fig. 22).

BN—3602

Figure 22.—Scab infections lblacl< spots) on

leaflets of the Schley variety of pecan in

early spring.

Infection of leaves, shoots, and

nuts by the scab fungus occurs during cloudy, rainy periods of spring

and early summer, when leaves remain wet for at least 12 hours.

Under such favorable conditions,

primary infections may occur before the middle of April and develop rapidly. Spores can germinate and cause infection within a

few hours. It is generally 1 or 2

weeks, however, before scab lesions

(diseased areas) can be observed on

new tissue of either leaves or nuts.

During damp periods new crops of

spores are produced in unsprayed

leaves by the last week of April or

the first week in May. These spores

cause secondary infections.

Primary infections first appear

as elongated, olive-brown lesions,

usually on the veins of the undersides of the leaves. At first the

spots are the size of pin points.

They soon enlarge and coalesce.

Later, with the development of

secondary infections, large areas of

the leaves may become almost black.

On the nuts, the spots of infection

are small, black, and circular. At

first they are slightly raised, but

later they may become sunken. The

nuts of highly susceptible varieties

may be so extensively infected that

practically the entire surface of the

nut will appear black.

Scab injury on Schley nuts is

illustrated in figure 23. Of the five

classes of nuts shown, only those of

class E are unmarketable. Nuts in

classes C and D are poor in quality,

however. Severely infected nuts

may drop prematurely, or they may

stop growing and remain attached

to the shoots.

Control

To reduce scab infection, knock

all old shucks and leaf stems off the

trees before leaves begin to come

out in the spring. If this is not

done, infection of the foliage by

rainwashed scab spores probably

will occur. After a rain or on

misty or foggy days, a slight jarring of branches will cause most of

the old, wet shucks and leaf stems

to fall.

25
Figure 23.—Nearly full-grown nuts of the

Schley variety classed according to degree

of scab infection: A, No infection; B, one to

three primary infections; C, four or more primary infections; D, a fe^ secondary infections; E, many secondary infections.

Wherever possible turn the

shucks, leaf stems, and leaflets

under with a plow, deep enough

that they will not be turned up

again by disk harrows or other

cultivation machinery.

Wliere winter cover crops are

planted—a practice followed in

most successful orchards—turning

under shucks and leaves is not practicable. In such orchards it is imperative that the trees be thoroughly

sprayed with a fungicide such as

Bordeaux mixture, dodine,'^ or

zineb, according to the general

spray schedule on page 49.

Removal of low limbs will make

it possible to plow near the trees.

It also will let more sunlight

through to the foliage and allow

better air circulation ; this will promote quicker drying of leaves and

nuts after rains and heavy dews,

and reduce chance of infection by

fungus spores. Low limbs may be

cut from the trees, or in mature

orchards they may be pruned by

allowing livestock to browse on

them.

Of all the materials tested for

control of scab, homemade low-lime

Bordeaux mixture (p. 47), dodine,

and zineb have given the best results. By applying these fungicides according to the schedule on

page 49, scab can be controlled to

the point where it will cause only

slight or no injury.

Proper timing and thoroughness

of the spray applications are important. Sometimes weather conditions are such that it is not possible to spray in time to prevent early

infection on the young nuts. If

later applications are properly applied to the trees, however, secondary infection can be prevented and

nuts of good quality probably can

be produced (fig. 24).

' The application of dodine injures the

leaves of some varieties such as Moore

and Van Deman ; it should not be used

on them.

26
BN-360^

Figure 24.—-These nuts of the Schley variety

were infected by scab early in the spring.

Primary infections produced the black, sunken

spots on the shucks. Secondary infection

was prevented by three applications of Bordeaux mixture, the last about July 15. Nuts

are shown as they appeared on October 1.

ROSETTE

Rosette is a nutritional disease

caused by zinc deficiency. The disease occurs when there is not enough

available zinc in the soil to meet the

requirements for pecan tree growth

and nut production.

Prior to the discovery in 1931 of

the cause and control of rosette,

most of the bearing pecan trees in

the Southeastern States were affected by the disease. Since that

time, the soils of most pecan orchards in that area have been

treated with zinc sulfate. Once

rosette is controlled in this way, it

is a minor problem and only an occasional application of zinc sulfate

is needed thereafter.

Rosette can occur under various

soil conditions throughout the areas

where pecans are grown. The disease causes serious damage both in

native groves and in orchards of

improved varieties.

The following soil conditions are

most commonly associated with

rosette: Lime-impregnated, sandy

loam, loamy sand, and deep sandy

soils deficient in organic matter;

eroded soils with little or no surface

soil remaining ; and fertile soils that

have been deeply and frequently

cultivated or that have received too

much fertilizer, especially nitrogen,

or lime.

A high percentage of the trees in

young orchards that are intercropped annually with cotton, corn,

or peanuts are likely to be affected

by rosette unless they are treated

with zinc sulfate.

In its earliest stages, or on

slightly affected trees, rosette appears as a yellowish mottling of the

leaves, particularly in the treetops.

In its advanced stages, the leaflets

are slightly narrowed and crinkled.

When the trees are severely affected,

the leaflets are extremely narrowed

and liave reddish brown areas or

perforations between the veins.

New shoot growth is checked, the

internodes are shortened, and the

foilage is therefore bunched, or

resetted, in appearance. The name

of the disease is derived from this

characteristic.

In the final stages of the disease,

the shoots die back from the tips.

Usually the die-back is confined to

the current year's growth, but sometimes it extends to older branches

of considerable size. Seriously affected trees rarely bear nuts, and

nuts that are borne are usually small

and poorly filled.

Foliage on badly rosetted trees

develops earlier in spring than that

on healthy trees, probably because

27
of tlie pruning effects of the dieback. Symptoms of the disease on

moderately or severely affected

trees become more pronounced as

the season advances, and by October or November the trees appear

at their worst. At this time the

foliage of seriously diseased trees

has a rusty or bronzed appearance,

especially when viewed from a

distance.

Control

To correct the condition that

causes rosette, apply zinc sulfate in

solution as a spray to the trees or

as a dry salt on the soil. Trees recover most rapidly from the effects

of rosette when they are sprayed,

but soil applications are to be recommended because of their lasting

effect.

For mild cases of rosette, make

3 spray applications to the trees.

Spray with a solution consisting

of 2 pounds of zinc sulfate, analyzing approximately .36 percent zinc,

in 100 gallons of water. Make the

first application as soon after pollination as possible and the other

two at intervals of 2 to 3 weeks.

This treatment must be repeated

annually until all signs of the disease have been eliminated. Thereafter, the trees should be closely observed for indications of the disease,

since it is likely to reappear at any

time.

To control scab and other parasitic disease at the same time rosette

is treated, dodhie, zineb or Bordeaux mixture can be combined with

zinc sulfate. Increase the propr)rtion of zinc sulfate (use 4 pounds

per 100 gallons of Bordeaux mixture), because the lime in the

Bordeaux mixture reduces the effectiveness of the zinc. To check

the corrosive action of the zinc sulfate on your equipment, rinse the

spray pump and tank thoroughly

after each day's spraying.

Applications of zinc sulfate to the

soil may be somewhat more expensive than spraying because the

chemical is often applied at higher

rates. Soil applications give more

lasting control of rosette, however.

Applications are usually effective

and relatively inexpensive on acid,

neutral, and light-textured alkaline

soils. On heavy-textured alkaline

soils or on soils that have a high

fixing power for zinc, extremely

high rates of application are usually

necessary, and spraying is generally

preferable.

Zinc sulfate is applied to the soil

in the same manner as fertilizers.

If necessary, it can be mixed with

a fertilizer. On soils that do not

have a high-fijsing power for zinc,

or when trees are not severely

rosetted, apply zinc sulfate at an

annual rate of 5 pounds per tree.

Severely rosetted trees require between 5 and 10 pounds of zinc sulfate amiuaUy for 2 or more years

(figs. 25 and 26). The larger the

dosage the first year, the greater

will be the improvement from the

diseased condition.

Make applications in late February or early March by broadcasting

the zinc sulfate evenly beneath the

trees, from near the trunk to beyond

the radius of the limbs. To insure

quick and positive incorporation,

disk or plow the zinc sulfate into

the soil, especially under the following conditions : On steep slopes that

28
Figure 25.—Pecan free seriously affected with rosette. Dead branches can be seen at top of the

tree. Leaflets on other branches are small, narrowed, curled, and yellowish green. Figure 26

shows the same tree after treatment with zinc sulfate.

may wash; on alkaline soils where

the zinc may be fixed in the surface

soil; or when there is not enough

moisture to dissolve the material

and carry it down into contact with

the absorbing roots. If you grow a

winter cover crop in your orchard,

distribute the zinc sulfate evenly

and in small amounts to avoid burning the crop; delay cultivation if

the chemical is applied in February

or March as recommended.

DOWNY SPOT

Downy spot is a fungus disease

that affects the leaves of pecans. It

occurs throughout the southern

pecan-producing region. The disease usually appears first in late

spring or early summer as downy

or "frosty" spots on the lower sides

of the leaflets (fig. 27). This appearance is due to production of

spores by the fungus. Later, after

29
' *» ^^:in ^

BN-3624

Figure 26.—The tree shown in fîgure 25 as it appeared 2 years later, after rosette had been

controlled by yearly broadcast applications of zinc sulfate to the soil.

these spores have been washed away

or have deteriorated, greenish-yellow spots about one-eighth inch in

diameter remain on both sides of tlie

leaves. These spots are clearly visible. As the season advances, the

color of the diseased parts changes

to brown. These parts of the leaves

die, and the result is a premature

defoliation of the trees.

The fungus that causes downy

spot lives over winter in the diseased leaves, where its life cycle is

completed. In early spring, especially during rainy periods, the

new leaves are infected by the large

number of spores expelled from the

fruiting bodies in the old leaves.

All pecan varieties are attacked

to some extent by the downy spot

fungus, but Burkett, Moneymaker

and Stuart are among the most

susceptible.

Control

To reduce infections of new leaves

by downy spot, plow under old diseased leaves in spring before tree

growth begins and before the fruit30
ing bodies release their spores.

Spraying trees according to the general spray schedule (p. 49), will

control downy spot and other diseases, particularly scab.

BN-3606

Figure 27.—Characteristic white or "frosty"

spots on the underside of a pecan leaflet

caused by the downy spot disease in its

early stages.

VEIN SPOT

Vein spot is a fungus disease that

attacks pecan leaves. It is prevalent in the southwestern part of the

Pecan Belt, including the States of

Arkansas, Louisiana, Mississippi,

Oklahoma, and Texas.

The resemblance of the lesions of

vein spot to those caused by scab on

the leaves is so close that one disease

may easily be mistaken for the

other. The spots characterizing

each disease may originate on the

veins of leaflets or on leaf stems

(rachises) and are dark brown or

black in the final stages. On lateral

veins, lesions caused by vein spot

are circular or oval and seldom attain a diameter of more than onefourth inch; on midribs of leaflets

and on leaf stems, spots are long

and narrow. On midribs, spots

sometimes extend from the base to

the apex of the leaflet. Unlike scab,

vein spot does not attack the shoots

or nuts, and the fungus apparently

invades tissues of leaflets only a

short distance on each side of the

veins (fig. 28).

Because vein spot fungus attacks

and kills the growing tissues of

leaves, premature defoliation often

follows moderate to severe infections. If leaf stems are severely

affected, the leaflets, and frequently

entire leaves, drop prematurely. If

leaflet stems (petioles) become

girdled and die, leaflets may hang

on the tree for a time.

The life history of tlie vein spot

fungus is similar to that of most

other fungi known to infect pecan

leaves. It lives through the winter

on fallen leaves. During early

spring, spores are formed ; they are

31
discharged into the air and infect

new leaves.

BN—3605

Figure 28.—Vein spot disease on a pecan

leaflet. Spots are darit brown or black in

the final stages of the disease.

Control

Use good sanitation practices and,

where possible, plow under leaves

and stems that are iiJiely to carry

the vein spot fungus. To control

the disease with fungicides, spray

the trees once before pollination

with 4-1-100 Bordeaux mixture and

once or twice after pollination with

zineb or 6-2-100 Bordeaux mixture. Make the second application

as soon after pollination as possible ; make the third 3 to 4 weeks

later. (See spray schedule, p. 49.)

LEAF BLOTCH

Leaf blotch is a fungus disease of

nursery and mature trees; it is

present throughout most of the

pecan-growing region. It is first

indicated by the appearance of

olive-green, velvety tuffs in June or

July (fig. 29). Yellow spots appear later on the upper surfaces

of the leaves. Fruiting bodies,

black pimplelike structures, make

their appearanc« about midsummer.

After tlie spores have been washed

away by rain or have otherwise deteriorated, groups of these pimplelike structures unite, giving the

leaves a black, shiny, blotched appearance. Occasionally these

blotches join to envelop entire leaflets, causing premature defoliation

of the tree.

The organism that causes leaf

blotch is a weak parasite and does

not attack orchard trees unless they

have been lowered in vigor by overcrowding, rosette, attacks by borers,

or general neglect. Nursery trees

are more susceptible, and the disease is especially prevalent where

nursery blight is present. Wlien

trees are infected with leaf blotch,

defoliation begins with the basal

32
BN-3607

Figure 29.—Early stage of leaf blotch on the

underside of a leaflet. The pimplelike fruiting bodies have just begun to form dark

blotches.

leaves. Tlie disease gradually progresses upward until defoliation is

complete except for a few leaves in

the tops of the trees.

Control

Plow under old leaves in early

spring to insure as high a degree

of cultural control of the leaf blotch

fungus as possible. Chemical control measures used against scab and

downy spot are also effective in controlling leaf blotch. Application of

dodine, zineb, or a 6-2-100 Bordeaux mixture will prevent the development of the disease. (See

spray schedule, p, 49. ) In localities

where only leaf blotch is present,

spray the trees two or three times

(first, second, and third cover

sprays) with either of these fungicides. Apply the first spray soon

after pollination takes place, and

the second and third after intervals

of 3 or 4 weeks.

BROWN LEAF SPOT

Brown leaf spot is a fungus disease of minor importance, especially on healthy trees. Although it is

found throughout the Pecan Belt, it

causes serious premature defoliation only in localities where there

is heavy rainfall or on trees that

lack vigor because of neglect.

Brown leaf spot first appears in

June or July and is found only on

the mature leaves. Primary infections are circular in outline (fig.

30) and are reddish brown; they

often develop grayish concentric

zones. As the disease progresses,

the spots become irregular in outline. If not controlled, the disease

may cause complete defoliation by

the first of October. Like other

leaf fungi, the brown leaf spot organism is carried over winter in

the infected spots on old leaves.

Control

To control brown leaf spot, spray

trees one or more times between

33
May 15 and June 15 with dodine,

zineb, or 6-2-100 Bordeaux mixture. (See spray schedule, p. 49).

LIVER SPOT

In some years, a fungus disease

known as liver spot causes considerable damage to pecan foliage ia

Mississippi, Louisiana, Arkansas,

and Texas. Evidence of this disease first appears in May or June

as dark-brown circular spots on the

lower surfaces of the leaflets, mainly along each side of the midrib

(fig. 31). Spots are usually i/g to

Figure 30.—Brown leaf spot on the underside

of a leaflet The diseased spots are often

characterized by concentric markings (not

visible in photographl.

Figure 31.—Early stages of liver spot on o

pecan leaflet.

34
s/g inch in diameter. In September

and October, the color of the spots

changes to a cinnamon brown, and

at about the same time, small, dark,

spore-bearing bodies appear in the

center of the spots. Leaflets that

have several spots will fall during

September or October. If spring

weather is damp and favorable for

numerous infections, severe premature defoliation may occur.

The fungus that causes liver spot

survives winter in a semidormant

condition on fallen leaves. Upon

return of moist, warm weather in

spring, the fungus produces spores,

which infect the new leaves.

The foliage of strong, vigorous

trees is noticeably more resistant to

attack than that of trees whose

vigor has been impaired by the keen

competition of weeds and grasses

for moisture and plant nutrients.

Control

Liver spot can be controlled by

the application of zineb, or 6-^100

Bordeaux mixture. The first application should be made at the time

of the first cover spray. This

should be followed by the second

and third cover spray applications.

(See spray schedule, p. 49).

CROWN GALL

Crown gall is a bacterial disease

that often causes damage to pecan

trees. It was formerly believed

that it affected only nursery trees

(fig. 32), but in recent years the

disease has been found well established in orchards—especially on

old trees, which it may affect severely enough to kill (fig. 33).

BN-3610

Figure 32.—Crown gall disease on nursery

stock. Trees so infected stiould be burned to

prevent further spread of the disease.

BN-3611

Figure 33.—This 20-year-old pecan tree has

been completely girdled by a large, wartlike

growth caused by crown gall.

On mature trees, the disease is

confined mostly to the large roots

and bases of the trunks, but occasionally smaller roots are also infected. Wartlike growths from a

few inches to a foot or more in

35
diameter, often extending several

inches above tlie soil surface, characterize the orchard-tree development of the crown gall disease. Because of the fragility of the galls,

they are often broken off from the

roots. The galls may then become

scattered on top of the soil when

the orchard is being cultivated,

thus spreading the disease organism.

Control

All nursery trees infected with

crown gall should be destroyed by

burning, preferably at the time of

digging. Only disease-free trees

should be planted in new orchards.

There is no effective and practical

control for crown gall on established trees. Do not cultivate the

soil near the trunks of infected

trees; the practice may spread the

disease.

BUNCH DISEASE

The characteristic symptom of

bunch disease is a bushy growth of

slender, willowy shoots that result

from an abnormal forcing of lateral buds into growth. Bunch disease appears to be infectious, and is

known to spread from tree to tree.

Apparently no parasite is associated

with the abnormal growth. In some

respects symptoms resemble those

of some virus diseases of other

woody plants such as peach yellows

and bunch disease of walnuts.

In trees lightly affected with

bunch disease, only portions of one

branch or of several scattered

branches will show the characteristic symptom. The bunch growths

are most conspicuous in spring and

early summer because their development is earlier and greater than that

of unaffected branches (fig. 34).

Seriously affected trees become

mere skeletons of main lateral

branches covered with a thick,

broomy, sucker growth. On such

trees, many leaflets die and fall in

late summer or early fall; some

shoots and branches also die, and

few if any nuts are produced.

Bunch disease spreads slowly

through a tree. Several years may

be required for all of a large branch

to become diseased after the first

evidence of infection appears.

Bunchy growths may arise from

the base of a tree or at a graft union, but similar growths may not

appear elsewhere on the tree for

several years.

Bunch disease may easily be confused with rosette. Two differences

can be noted on leaflets, however.

Those affected by bunch disease do

not become yellow between the

veins, nor do they become extremely

crinkled as do leaflets affected by

rosette.

Bunch disease has been observed

on water hickory and commercial

pecan varieties as well as on wüd

trees. Different varieties show

some difference in susceptibility to

bunch disease.

Tlie geographic range of bunch

disease appears to be limited to

nreas having rich, alluvial soils m

parts of Arkansas, Louisiana, Mississippi,Oklahoma, Texas, and New

Mexico.

Control

N"o measures are known that will

definitely control bunch disease.

Never use bud or scion wood from

diseased trees for propagation. It

36
Figure 34.—Effects of bunch disease on a pecan tree in early spring. Diseased branches often

put out leaves about 2 weeks earlier than healthy branches.

is imperative also to use only disease-free pecan or water hickory

trees as stocks in top-working native trees to standard varieties.

Destroy any diseased pecan or hickory trees that may be growing wild

in the vicinity of your orchard. On

lightly affected trees, j'ou may be

able to arrest the disease by pruning out diseased branches. Make

the cuts well back from infected

parts. Once a lateral branch is affected as far back as the trunk or a

main limb of a tree, there is little

hope of arresting the disease. Trees

so affected should be destroyed immediately. The more susceptible

varieties, such as Schley, Mahan

37
and Desirable, should not be propagated in locations where bunch disease is prevalent.

WOOD ROT

Broken branches or other wounds

on pecan trees provide possible

points of entrance for wood-rotting

fungi unless the injured surfaces are

properly treated. Once these fungi

gain entrance, they spread rapidly

through the wood and may destroy

the entire tree.

Control

Cut off broken branches or limbs

flush with the main branches or

trunk of the tree (fig. 35). Do not

leave projecting stubs; they rarely

heal over and thus COTitinue to provide entrances for wood-rotting

fungi. Smooth wounds heal more

quickly than do those that have

rough or jagged surfaces. Paint

the wounds with a mixture of one

part of creosote to three parts of

coal tar to protect the surfaces; repeat this treatment once a year until

the wounds have healed. This mixture is caustic and will slightly injure the cambium (growing layer),

but the wounds will usually remain

free of wood-rotting fungi, and

eventually will heal. Commercial

paints for tree wounds, having asphalt, tar, or vegetable gums as

their base, may also be used to cover

wounds.

BN-3Í13

Figure 35.—Tree at left has been improperly pruned. Wounds of this type heal slowly and

provide entrances for wood-rotting fungi. Tree at right has been pruned properly and hos

healed rapidly; cuts were made flush with trunk and treated with the recommended mixture

of coal tar and creosote.

38
COTTON ROOT ROT

Cotton root rot is a disease caused

by a soil-inhabiting fungus. The

disease has been found in Texas and

other States westward to the Pacific

coast. Although cotton root rot

most commonly attacks cotton and

alfalfa, it is harmful to many other

plants. It has killed pecan trees

inboth Arizona and Texas.

The fungus is most active during

the summer. Injury to tlie roots

reduces the moistvire and mineral

supply to the tree tops, which causes

the death of trees. Some trees continue to live through one or two

seasons, however, after symptoms

of the disease become apparent. In

such cases, the leaves may be yellow

and sparse.

There is no practical means of

controlling cotton root rot. It is

suggested that growers avoid planting pecan trees in soil known to be

infected with this fungus, especially

where cotton or alfalfa has been

killed by it.

POWDERY MILDEW

Powdery mildew usually is considered to be of minor importance

on the pecan, although it occasionally causes serious damage to the

nuts. This fungus disease affects

both foliage and nuts; it forms

white superficial growth (fig. 36)

early in the growing season, usually

in July. Premature defoliation of

the trees occurs when conditions are

especially favorable for the spread

and development of the fungus.

When the nuts are infected early in

the growing season, those tliat develop may be small, the shucks may

split prematurely, and the kernels

may be shriveled. During the winter the fungus remains dormant on

infected leaves and shucks.

BN-3614

Figure 36.—Early stages of powdery mildew

on pecan nuts of the Farley variety. The

characteristic white gro^wth has covered most

of the surface of the nuts.

Control

To reduce infections caused by

powdery mildew, plow under old

leaves and shucks in spring before

spores are released. Control of the

disease with fungicides is relatively

easy if spraying is done at the right

time. Spray trees twice with zineb,

or 6-2-100 Bordeaux mixture.

Apply as the third and fourth cover

sprays with an interval of 3 to 4

weeks between applications. (See

spray schedule, p. 49.)

NURSERY BLIGHT

Seedling trees that are severely

affected by nursery blight make

little growth and are often too small

for budding at the end of the second

season. As its name implies, this

disease is confined almost entirely

to nursery trees.

39
The fungus that causes nursery

blight invades both young and old

leaflets. Infections begin in April,

developing into small reddish

lesions on both surfaces (fig. 37).

Later in the growing season, the

spots on the upper surfaces turn

gray. Single lesions are usually

about one-eighth inch in diameter.

These spots may be united by secondary infections to form a continuous lesion along each side of a vein.

Secondary, or late, infections are

most numerous along the midribs

and larger veins. The diseased

areas soon are killed by the invading fungus, and the tissues become

brittle and break. The affected

leaflets then have ragged margins

and perforations.

Control

For control of nursery blight,

spray the trees once with 4-1-100

Bordeaux mixture when the first

leaves that form are half grown.

Follow this spray application with

three applications of zineb, or &-2~

100 Bordeaux mixture at intervals

of .3 to 4 weeks. ( See spray schedule, p. 49.)

PINK MOLD

During late summer and early

fall, a pinkish fungus growth

known as pink mold can frequently

be observed on the shucks of nuts

that have been attacked by scab

(fig. 38). The pink mold fungus

invades the shucks mostly through

the scab spots. It continues to de-

^KÊ^'X^H Pi

BËMm

i

Figure 37.—Early stages of nursery blight on a

pecan leaflet.

BN-3616

Figure 38.—Nuts of the Schley variety affected

with pink mold. Scab lesions are visible on

the nut at the upper right.

40
vdop after the nuts have matured.

The fungus may enter the inside

of the nuts and attack the kernels.

There it causes a decay known as

"pink rot." Nut kernels affected

with pink rot leak oil and often gi^-e

off a strong, rancid odor. The shells

usually have an oily appearance.

Nuts of the Schley variety, particularly those grown on unsprayed

trees, are often seriously affected by

pink mold. Only a part of the crop

may be marketable if many of the

nuts have been infected.

Control

Pink mold attacks chiefly scabinfected nuts, and only when these

nuts are still on the trees. After

harvest, the mold does not spread

from infected to sound nuts. To insure control of the disease, follow

the spray program for the control

of scab described on page 49.

LICHENS

Lichens frequently occur on the

trunks and branches of pecan trees,

usually in the humid climate of the

gulf coast. These growths give the

trees an unkempt appearance but are

usually considered to be harmless.

Lichens are low forms of plant

life that grow in humid localities.

They are not single plants but are

composite organisms made up of

algae in enveloping meshes of fungus filaments. Like mosses, lichens

obtain their food chiefly from air

and water, and they attach themselves not only to trees (trunks,

branches, and occasionally leaves)

but also to such objects as fenceposts and rocks.

A common form of lichen is the

grayish green, paperlike growth

that occurs on the bark of pecan

trees (fig. 39). This irregularly

shaped growth varies from nearly

an inch to several inches across. Its

edges are usually lobed and curled

upward.

BN-3631

Figure 39.—Lichens on bark of pecan tree

branch.

Control

Because lichens are usually considered to be harmless to pecan trees,

no spray program has been worked

out for their control. However, almost any standard fungicide, including Bordeaux mixture, and solutions containing organic coppers,

will readily control lichens. Lichen

growths are never found on trees

that are sprayed regularly with

Bordeaux mixture for the control of

scab and other pecan diseases.

41
SPANISH-MOSS

The common gray moss, or Spanish-moss (Tillandsia usneoides),

occasionally becomes unsightly and

injurious on pecan trees. It is usually most troublesome in neglected

orchards located in areas having

poor air movement and high humidity, especially when live oak trees

are growing nearby. Spanish-moss

is not a true moss, but an epiphytic

plant—one that has no true roots.

Its nourishment is derived from the

air, rain, and dew. It grows not

only on trees but also on many inanimate objects. Large accumulations of Spanish-moss are detrimental to tree vigor and growth because of their shading effects (fig,

40.)

Control

Spanish-moss needs sunlight for

heavy growth. To keep it in check,

therefore, make sure orchard trees

are vigorous so they will provide

maximum shade. An efficient cultural and fertility program usually

will invigorate trees enough to

keep the moss in check. Spray

trees with a mixture of 10 pounds

Figure 40.—Accumulation of Spanish-moss on a pecan free.

42
of copper sulfate and 10 pounds of

calcium arsenate in each 100 gallons of water. Spray them annually while they are dormant, preferably in February or March. Three

annual applications are usually

sufScient to eliminate moderate infections. Do not allow livestock to

graze in orchards for 2 weeks after

spraying with calcium arsenate.

INJURY CAUSED BY CLIMATIC CONDITIONS

WINTER INJURY

Winter injury is a disorder usually found on young, vigorous, lategrowing pecan trees. It also occurs on trees that have prematurely

lost their leaves and then have put

out new leaves late in the growing

season. If such trees have not become dormant before freezing

weather, their growing tissue is

likely to be injured, particularly

near the base of the trunk. During

the next spring, severely affected

trees usually leaf out and appear

to grow normally. However, as

soon as hot weather begins, the

leaves wither and the trees suddenly die.

Winter injury is easily detected.

The bark on the injured area appears sunken and is cracked where

it meets the growing tissue, which

is discolored and sour smelling.

The roots of affected trees seldom

die, but sprout from below the dead

trunks. Shothole borers and other

insects are sometimes present, but

their damage is of a secondary

nature.

Proper cultivation, fertilization,

and spraying do much to prevent

winter injury. Cultivation should

not ordinarily be continued later

than midsummer. However, an

orchard may be cultivated as part

of the planting of winter cover

crops in fall, when trees are approaching dormancy. The trees

should be fertilized only in early

spring. Spraying to control diseases and leaf-destroying insects

should be done at the proper time.

If these practices are followed,

trees will have a good chance of

escaping premature defoliation and

of going into winter in a mature

and hardy condition.

SUNSCALD

Injury from sunscald is sometimes confused with winter injury.

The symptoms are dead or cankerous areas, usually on the southwest

side of the trunk or on the upper

surfaces of large branches. Like

winter injury, sunscald occurs

mostly on young trees, but it also

occurs on older ones that have been

cut back for topworking to some

other variety.

Bright sunshine, which raises the

temperature of unshaded bark to

the killing point, is probably the

sole cause of sunscald in summer.

During winter, the condition probably is caused by the combined effect of bright sunshine and a sudden, usually severe, drop in temperature at the end of the day. The

dead areas below the bark furnish

ideal points of entrance for borers

and other insects and for wood-rotting fungi.

43
One of the best methods of preventing injury from sunscakl is to

head the young trees low so that

the branches will shade the trunk.

Because the lower limbs give protective shading to the trunks of

young trees, they should not be

trimmed off until the trees have

made several year's growth.

Wrapping the trunks of young

trees with gunny sacks or paper,

or whitewashing them, will also aid

in preventing sunscald.

LIGHTNING INJURY

Lightning strikes young and mature pecan trees causing injury or

even death to them. Such injury

is often mistaken for the effect of

some parasitic disease.

TVlien a pecan tree is struck by

lightning, the principal visible injury may be confined either to the

limbs and branches or to the trunk.

There may be a narrow split in the

bark, extending from a branch in

the top down the trunk to the

ground, or the bark may be completely peeled from the trunk, esr

pecially near the ground. If the'

bark is only split, the tree usually

survives ; if the bark is loosened or

peeled from the trunk, the tree dies

within a few weeks.

—The bark of the trunk of this tree was split to the ground by lightning,

the branches died in about 4 weeks, but the rest of the tree later recovered.

44
"Í^ÍL^ V^V vi',

BN-3619

Figure 42.—Pecan free killed by lightning,

shown as it appeared 3 months after having been struck. Note how the bark was

stripped from trunk.

Trees struck by lightning usually

undergo partial to complete defoliation, depending on the extent of

the injury. Leaves of affected

areas first turn yellow and later

drop. A tree can become completely defoliated within 30 to 60

days after being struck. Apparently, definite signs of lightning injury are confined to the trees that

receive direct hits.

There is no practical way to prevent damage from lightning in an

orchard, but trees killed or injured

by lightning should be treated

promptly. If a tree is killed, it

should be destroyed; otherwise it

may become infested with borers

that probably will spread to other

trees. Dead limbs should be removed. Wounds left after such

pruning should be painted with a

mixture of coal tar and creosote as

recommended for the control of

wood rot. Spraying injured trees

with 4 pounds of 60-percent DDT

wettable powder in each 100 gallons

of water, will aid in preventing infestation by borers. Also, wounds

and cracks in the bark should be

painted with neutral asphalt or a

pruning compound to prevent rapid

drying and borer infestation. If

injured trees are properly cared

for, most of them eventually recover.

INSECTICIDES AND FUNGICIDES

PRECAUTIONS

Insecticides and some fungicides

are poisonous. Handle them with

care. Follow the directions and

precautions for use and safe handling given on the labels on containers. Store insecticides and

fungicides in plainly marked containers away from all food products, in a dry place where children

and domestic animals cannot reach

them. Wlien mixing and applying

them, take care to keep the materials out of the mouth and eyes and

away from the tender parts of the

body. Wash the face and hands

thoroughly after applying any insecticide. After long exposure, take

45
a bath and change clothing. Wash

clothing on which spray residues

have accumulated before wearing it

again.

If overexposure to insecticide results in ill effects, consult a physician immediately. If you swallow

an insecticide or fungicide, induce

vomiting immediately. Then call

your physician, lie down, and keep

quiet. If your physician needs information concerning sjrmptoms

and treatment of actual or suspected

poisoning by a pesticide, have him

call his nearest poison control center or the U.S. Public Health Service at its nearest office.

Empty containers are hazardous.

Empty bags and packages should

either be burned in the open or

buried; metal containers should be

crushed and buried. Avoid breathing dusts or vapors when crushing

empty bags, packages or metal

containers.

To protect wildlife, do not contaminate streams, lakes, or ponds

with pesticide chemicals.

Do not allow dairy cows or animals being finished for slaughter

to feed on vegetation under trees

that have been treated with insecticide. Remove grazing animals

from orchards during spraying and

keep them out until residues decline

to a safe level. This will be about

2 weeks if phosphorus insecticides

other than parathion have been applied, and considerably longer (exact time not known) if chlorinated

hydrocarbon insecticides have been

used.

Insecticides such as demeton,

EPN, Guthion, parathion, TEPP,

and Trithion are extremely poisonous and may be fatal if swallowed

inhaled, or absorbed through the

skin. Do not use them in small

home plantings. They should be

used only by a person thoroughly

familiar with their hazards and

who will assume full responsibility

for safe use and comply with all the

precautions on the labels. Handle

them only in the open air or in a

well-ventilated room.

Do not use TEPP later than 3

days before harvest, demeton and

EPN later than 21 days before harvest, or Guthion, parathion, and

Trithion after the shucks begin to

open.

INSECTICIDES

BHC, DDT, dinitro insecticides,

lindane, malathion and toxaphene

are insecticides that can be handled

safely as recommended for controlling pecan insects by following the

precautions on container labels. Do

not use dinitro insecticides after the

buds begin to swell; do not use

BHC or lindane after the nuts are

present. DDT, malathion, and

toxaphene can be used at any time,

as needed, before the shucks spht.

Oil sprays can be used as needed,

since they are exempt from a tolerance. Pecan trees are less tolerant

of dormant oil spraysthan are many

kinds of deciduous tree fruits. It

is important, therefore, to follow

directions carefully to obtain the

recommended quantity of oil in the

dilute spray. Do not apply an oil

spray when temperatures are below

50° F. or over 90°. Use an oil of

near 100 seconds Saybolt viscosity

for dormant treatments; use a

highly refined oil of nearly 70 seconds Saybolt viscosity and with an

46
unsulfonated residue of at least 85

to 90 percent for summer treatments.

FUNGICIDES

Bordeaux mixture.—A 6-2-100

formula for Bordeaux mixture requires 6 pounds of powdered copper

sulfate and 2 pounds of hydrated

lime in enough water to make 100

gallons of spray material. Smaller

or larger quantities of the same

formula can be made by changing

the amounts of each ingredient in

proportion.

To make 500 gallons of 6-2-100

Bordeaux mixture use the following

procedure : Weigh out 30 pounds of

powdered copper sulfate and 10

pounds of hydrated lime. Add

about 10 gallons of water to tlie

lime in a separate container to make

a slurry. The copper sulfate may

be dissolved by placing it in the

strainer of the sprayer tank while

the tank is being filled with water.

When the tank is about threefourths full and all the copper sulfate is dissolved, add the lime

slurry slowly. The agitator should

be running so that the lime will be

thoroughly mixed with the copper

sulfate solution. After the lime

slurry is added, finish filling the

tank with water. Bordeaux mixture is exempt from tolerances.

Bordeaux mixture can be combined with insecticides, except toxaphene, without loss of its effectiveness. It is therefore possible to

spray against insects and diseases

m the same operation.

Dodine.—Dodine ' is the coined

name for the chemical n-Dedecylguanidine acetate, which is the active fungicidial agent. It is formulated as a 65-percent dry wettable

powder. Dodine is widely compatible with a large variety of other

spray materials and insecticides. It

is not compatible with lime or other

alkaline products. Limited use on

pecan has resulted in superior control of pecan scab on most varieties.

On some varieties, such as Moore

and Van Deman, dodine has caused

severe injury and should not be

applied.

Dodine should be used at the rate

of 0.5 to 1.0 pound of the 65-percent

wettable powder in each 100 gallons

of water; strength of the mixture

should depend on the season and

the severity of the scab situation.

The dry, wettable powder should be

added directly to the spray tank,

when the tank is half full and the

agitator is running.

There is no tolerance for dodine

on pecan. Do not apply more than

700 gallons of diluted spray material per acre of orchard per application. Do not apply dodine

after the shucks have started to

split.

Zineh.—Zineb ' formulations containing the effective fungicidal

chemical, zinc ethylene bisdithiocarbamate, are available as 65-percent, dry, wettable powders. These

fungicides are compatible with all

the recommended insecticides. The

65-percent material usually is applied at the concentration of 2

pounds of packaged material in

each 100 g-allons of water.

" Dodine is available under the trade

name or designation Cyprex 65W.

' Zineb formulations are available

under the trade names Dithane Z-78,

Parzate, and others.

47
To make 500 gallons of spray

material, use 10 pounds of a zineb

formulation. Place the material in

a container and add enough water

to make a paste. Add water to the

paste until it becomes a slurry (thin,

watery mixture). As the spray

tank is nearly filled with water, and

the agitator is running, add the

slurry. Delaying the addition of

the slurry will permit a more nearly

complete suspension of the zinc

salts in the water. Insoluble zinc

salts are hea\^ and soon settle to

the bottom of the tank unless the

mixture is constantly agitated while

spraying is underway. One quart

of summer-oil emulsion added to

each 100 gallons will give the spray

material good sticking quality.

There is no residue tolerance for

zineb on pecans. Do not apply

zineb later than 4.5 days before

harvest.

SPRAY MACHINES

New types of spray machines depend on a strong blast of air to

carry the spray through the trees.

Some are designed to apply spray

materials in a more concentrated

form than commonly used. Only

the most powerful machines of this

type are suitable for treating orchards that have large trees. Portable spray outfits are commonly

used for treating pecan trees. They

are either equipped with 15- to 35-

liorsepower motors or driven by

power takeoff on tractors or trucks.

The sprayer tank should hold at

least 400 to 500 gallons. The machine should have a pump capacity

of 20 gallons or more per minute

and maintain a pressure of 400 to

600 pounds per square inch with

the spray gun open. Trees from 40

to 60 feet high can be sprayed with

machines of this type.

The operator must be prepared

to spray parts of the trees at close

range and other parts at comparatively long distances. Therefore, a

spray gun equipped with a number

12 or 14 disk that can be adjusted to

produce either a wide-angled mist

or a narrow, driving spray is preferable. Tree tops can be sprayed

most throughly by standing on top

of the spray machine or in a tower

attached to the top of the machine, i

A high-pressure hose three-fourths .

inch in inside diameter is best.

A grower who has a small orchard

of young trees may use a smaller : machine tlian the ones described. |

If possible, sprayers should be pur- \

chased from a dealer who carries i

a supply of parts and equipment for !

needed replacements. ;

Airplane applications of concen- I

trated spray materials have been

used effectively for controlling •;

aphids, mites, some leaf feeding insects, and the pecan leaf casebearer. j

They have not been entirely satis- I

factory for controlling the pecan ;

nut casebearer, hickory shuckworm, i

pecan weevil, or pecan diseases.

48
Spray schedule for control of pecan insecfs and diseases

Spray, and time of application Insect or disease to be controlled Spray material, and amount to mix in

100 gallons oí water

Remarks

First prepoUination spray, when Scab or downy spot. 4-1-100 Bordeaux mixture

or

65-percent dodine, 0.5 pound.

buds are bursting and first

leaves are showing. To prevent foliage injury, apply

only when temperature is above

55° F. Second prepoUination spray,

when first leaves are half

grown.

Scab, downy spot, vein spot,

liver spot, or nursery blight.

4-1-100 Bordeaux mixture

or

6.5-percent dodine, 0.5 pound.

Pecan leaf casebearer 15-percent parathion 2 pounds

or

25-percent malathion, 3

pounds.

First cover spray, when tips of

small nuts have turned

brown.

Scab, downy spot, vein spot,

leaf blotch, brown leaf spot,

liver spot, or nursery blight.

6-2-100 Bordeaux mixture

or

65-percent dodine, 1 pound

or

65-percent zineb, 2 pounds

plus 1 quart summer-oil

emulsion.

Pecan nut casebearer, pecan

leaf casebearer, aphids, or

mites.

50-percent DDT, 2 or 3

pounds

or

15-percent parathion, 2

pounds

or

25-percent EPN, 2 pounds

or

25-percent Guthion, 2 pounds.

Use the smaller quantity of DDT

in the Southeast, and the larger

quantity elsewhere. If pecan

nut casebearer infestations are

heavy, make a second application 1 week later with any of the

insecticides listed. Use parathion if aphids and mites require

treatment. Two-percent parathion dust at SO pounds per

acre, or 10-percent malathion

dust at 40 pounds per acre may

also be used.

Rosette 4 pounds zinc sulfate in

Bordeaux mixture.

Reduce zinc sulfate to 2 pounds if

Bordeaux mixture is not used.
Ul

o

Spray schedule for control of pecan insects ancf diseases—Continued

Spray, and time of application Insect or disease to be controlled Spray material, and amount to mix lit

100 gallons of water

Remarlis

Second cover spray, 2 to 3 weeks

after first cover spray.

Scab, downy spot, vein spot,

leaf blotcli, brown leaf spot,

liver spot, nnrsery bliglit,

powdery mildew.

6-2-100 Bordeaux mixture

or

65-percent dodiue, 1 pound

or

65-percent zineb, 2 pounds

plus 1 quart summer-oil

emulsion.

If fall webworms or caterpillars are

abundant, add 2 pounds of 50-

percent DDT, or 15-percent

parathion, or 25-percent EPN,

or 25-percent Guthion, or add 3

pounds of 25-percent malatliion

in each 100 gallons.

If sufiicient aphids or mites are

present to require control, use

insecticides recommended on

pp.9, 10, and'20.

Zinc sulfate, 4 pounds in Bordeaux mixture.

Reduce zinc sulfate to 2 pounds if

Bordeaux mixture is not used.

Third cover spray, 2 to 3 weeks

after seconil cover spray.

Scab leaf blotch, brown leaf

spot, liver spot, nursery

bliglit, powdery mildew.

6-2-100 Bordeaux mixture

or

65-percent dodine, 1 pound

or

65-percent zineb, 2 pounds

plus 1 quart summer-oil

emulsion.

If sufficient aphids or mites are

present to require control, use

insecticides recommended on pp.

Pecan leaf casebearer, aphids, 9, 10, and 20.

and mites.

50-percent DDT, 2 pounds

or

15-percent parathion, 2

pounds

or

25-percent Guthion, 2 pounds

or

25-percent EPN, 2 pounds.

Zinc sulfate, 4 pounds Reduce zinc sulfate to 2 pounds if

Bordeaux mixture is not used.
Fourth cover spray, 2 to 3

weeks after third cover spray.

Scab, powdery mildew _ _

Pecan weevil

Aphids and mites.

6-2-100 Bordeaux mixture

or

65-percent dodine, 1 pound

or

65-percent zineb, 2 pounds

plus 1 quart summer-oil

emulsion.

50-percent DDT, 6 pounds

or

40-percent toxaphene, 6

pounds

or

25-percent EPN, 2 pounds.

For best control of weevils, apply

combination spray material when

as many as six can be jarred from

a tree; apply it again in 10 days

to 2 weeks. Toxaphene may be

mixed with zineb, but not with

Bordeaux mixture.

If sufficient aphids and mites are

present to require control, use

insecticides recommended on pp.

9, 10, and 20.

Fifth cover spray, about Au- Scab _ 66-pereent dodine, 1 pound

or

65-percent zineb, 2 pounds

plus 1 quart summer-oil

emulsion.

These applications will also control

the leaf casebearer.

In dry seasons, the fungicide for

the sixth and seventh cover

sprays for scab can be omitted.

gust 10 to 15.

Hickory shuckworm 25-percent EPN or Guthion,

2 pounds.

Sixth cover spray, 2 weeks after

fifth.

Scab

Hickory shuckworm

Same as for fifth cover spray.

Seventh cover spray, 2 weeks

after sixth.

Scab

Hickory shuckworm

Same as for fifth cover spray.
The mention of commercial products in this publication

does not constitute an endorsement by the U.S. Department of Agriculture over other products not mentioned.

NAMES OF PECAN INSECTS, DISEASES, AND CAUSAL

ORGANISMS

Listed below are the common and scientific names of insects, diseases,

and causal organisms discussed in this publication.

INSECTS

Common name Scientific name

Hickory shuckwonn Laspeyresia caryana

Pecan nut casebearer Acrobasis caryae

Pecan weevil Curculio caryae

Black pecan aphid Melaiiocallis caryaefoliae

Black-margined aphid Monellia costalis

Southern green stink bug Nezara viridula

Leaf-footed bug Lcptorjlossiis phyllopus

Pecan leaf casebearer Acrohasis ¡uglandis

A spittlebug Cla.itoptera achatina

Fall webworm Hyphantria cunea

Walnut caterpillar Datana integerrima

Twig girdler Oncirleres cingulata

Pecan phylloxera PhyUoxcra devastatrix

Obscure scale C'lirysomphalus obscurus

A mite Eotetranychus hicorlae

Pecan bud moth Gretcliena bolliana

Flatheaded apple tree borer Chrysobothris femorata

May beetles or .June bugs Phyllophaga spp.

Red-shouldered shot-hole borer Xylobiops basilaris

Hickory shoot curculio Conotrachelus arattis

Other curculios Conotrachelus pecanae and hicoriae

PECAN DISEASES AND CAUSAL ORGANISMS

Nome of disease Causal organism

Scab Fusicladiiim effustim

Downy spot Mycosphaerella caryigena

Vein spot Onomonia nerviseda

Leaf blotch Myco.tphaereUa dendroides

Brown leaf spot Cercospora fusca

Liver spot Onomonia caryae var. pecanae

Crown gall Agrobacterium tumefaciens

Cotton root rot Phymatotrichum omnivorum

Pou-dery mildew Microsphaera alni

Nursery blight Elsinoe randii

I'ink mold Cephalotheclum roseum

52

U.S. GOVERNMENT PRINTING OFFICE; 1963 O—663409