control

LIBRA R_i

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JAN 2 01959 •

insect pests

of greenhouse

vegetables

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AGRICULTURE HANDBOOK NO. 142

U.S. DEPARTMENT OF AGRICULTURE/'ß
CONTENTS

Insecticides 2

Precautions 2

Calcium arsenate 2

Chlordane 2

DDT 2

Lindane 3

Malathion 3

Metaldehyde 3

Nicotine 3

Parathion 4

Rotenone 4

Sulfur 4

TEPP 4

General control program 4

Sanitation 5

Soil sterilization 5

Insecticide applications... 6

Control in small greenhouses. . 8

Insect pests 8

Aphids 8

Armyworm 9

Page

Insect pests—Continued

Beetles 10

Cabbage looper 11

Corn earworm 11

Cutworms 12

Earwig 13

Fungus gnats 13

Garden fleahopper 14

Garden symphylid 15

Greenhouse leaf tier 16

Greenhouse whitefly 16

Mealybugs 18

Mites 18

Slugs and snails 21

Sowbugs 22

Thrips 22

Tomato pinworm 23

Wireworms 24

Common and scientific names

of insect pests of greenhouse

vegetables 25

Smith, Floyd Franklin, 1900-

Control of insect pests of greenhouse vegetables. [Washington, U. S. Govt. Print. Off., 1958]

25 p. iUus. 24 cm. (U. S. Dept. of Agriculture. Agriculture

handbook no. 142)

1. Greenhouse plants—^Diseases and^ pests. 2. Vegetables—^Dis~

eases and^ pests. 3. Insects, Injurious and beneficial. I. Title.

(Series)

SB603.S58

U. S. Dept. of Agr. Libr.

for Library of Congress

632.9

lAg84Ah no. 142

t

Agr 58-387

Washington, D. C. Issued January 1959

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

Washington 25, D. C. - Price 15 cents
control of insect pests

of greenhouse vegetables

By FLOYD F. SMITH, entomologist, Entomology

Research Division, Agricultural Research

Service

Approximately 2,400 acres of greenhouse vegetables are grown in the Northern United States. One-fourth of the

total acreage is in Ohio. Other important

areas are located in the New England

States, particularly Massachusetts, and in

Illinois, Indiana, Iowa, Pennsylvania,

New York, and Kentucky. Some vegetables are grown commercially in small

ranges or alternated with floral crops in

many greenhouses throughout the Northern States. In addition, the number of

small backyard greenhouses is rapidly

increasing. Vegetables as well as flowers

are being grown for home consumption

or local markets.

The annual gross sale of commercial

greenhouse vegetables amounts to approximately $50 million. To construct

2,400 acres of new greenhouse areas at

current prices would cost about I240

million.

Tomatoes are the most important

greenhouse vegetable, cucumbers are

second, and lettuce is third. Watercress,

endive, and radishes are also grown.

Insects and related pests have been a

serious problem to producers of greenhouse vegetables. Fall crops of cucumbers and tomatoes have been an uncertainty, and spring crops have been terminated early because of thrips and twospotted spider mites. At least 30 species

or groups of closely related species of insects, mites, slugs, snails, sowbugs, and

symphylids feed on the foliage or fruits

or attack the stems, roots, or the seedlings.

Since the development of more effective insecticides for these pests, such as

DDT, parathion, malathion, TEPP, and

lindane, both fall and spring crops can be

grown at will. Aerosol bombs have become standard equipment in most greenhouses and have further simplified pest

control. These improvements have resulted in greater production, much higher

quality crops, and considerable savings

for the grower in both time and cost.

However effective the new insecticides

may be, good cultural practices, sanitation, and soil sterilization are essential

for reducing or eliminating diseases, as

well as insect pests, and for preventing

their continued damage to succeeding

crops.
INSECTICIDES

Precautions

Insecticides are toxic to man as well as

to insects. Adequate safeguards must be

used and precautions must be followed to

protect the workers that apply them as

well as those that work in the greenhouse

after applications have been made. Also

the grower must protect the consumer

from harmful residues by maintaining a

safe interval between the last insecticide

application and harvest. Follow the directions and heed all precautions on the

container label.

Parathion, TEPP, and methyl chloride,

which is contained in greenhouse aerosols, are extremely poisonous. Parathion

and TEPP in any form and any greenhouse aerosol regardless of the insecticidal ingredient should be applied only by

a trained operator who will enforce the

precautions prescribed by the manufacturer and assume full responsibility for

safety. Do not use these materials in

greenhouses connected to living quarters.

Do not use parathion on tomatoes within

10 days, on cucumbers or radishes within

15 days, or on lettuce or endive within 21

days before harvest. Do not apply TEPP

to any vegetable within 3 days before

harvest.

Do not use malathion on cucumbers

within I day, on radishes within 7 days,

or on lettuce, endive, or watercress within 10 days before harvest. Do not apply

to tomatoes a malathion aerosol within

15 hours or a malathion spray within 3

days before harvest.

Do not apply DDT to tomatoes or cucumbers within 5 days before harvest or

to lettuce or endive after the seedling

stage.

Do not apply DDT to watercress. Do

not apply parathion to watercress after

the foliage to be eaten appears.

Do not apply calcium arsenate or chlordane to any vegetable crop after the edible

parts appear.

Do not apply metaldehyde dust to any

vegetable after the foliage or fruit intended to be eaten is present. Metaldehyde baits can be used at any time.

Do not apply nicotine to tomatoes, radishes, or cucumbers within 3 days or to

lettuce, endive, or watercress within 7

days before harvest.

To avoid excessive residues on greenhouse vegetables, use all insecticides at

the recommended rate. To avoid plant

injury, stunting, or abnormal growth, use

preparations containing highly refined

toxicants.

Calcium Arsenate

Calcium arsenate is not recommended

against pests of greenhouse vegetables,

except against slugs and snails when it

is mixed with metaldehyde in commercially prepared baits. (See p. 21.)

Chlordane

Use chlordane for controlling pests

outside vegetable greenhouses, for soil

treatment against wireworms, and for

incorporation in metaldehyde baits

against slugs and snails. Apply chlordane dusts to control earwigs in areas

outside the greenhouse. Do not apply

chlordane dusts or baits to vegetables

after parts of the plant to be eaten or

marketed appear.

DDT

A 3-percent DDT dust is useful in

the control of many pests. Apply the

dust at 30 pounds per acre, or at i

pound per 1,500 square feet, with a portable duster driven by hand crank or electric motor. Discharge the dust into the

air above the plants so that it settles in a

light uniform deposit on the foliage and

leaves a minimum amount of residue.

Excessive applications from uneven distribution by inferior dusters or careless

workers are likely to injure the plants and

leave undesirable residues. A DDT dust

is safer and more economical than a DDT

aerosol for the control of thrips, corn

earworms, and tomato pinworms. DDT

dusts are safer than DDT sprays, which

are useful in small greenhouses only.

DDT aerosols available for use on ornamentals should be applied to vegetables

only if directions for such use are on the
label. A 5-perGent DDT aerosol containing a special solvent is available for use

on vegetables, but cucumbers are sometimes susceptible to injury. Most DDT

aerosols cause bleaching of cucumber foliage. However, a special DDT aerosol

that is generally safe for use on this crop

is available. If the label does not specify

that the DDT aerosol can be used safely

on cucumbers, use a 3-percent DDT dust.

Lindane

Use lindane to control garden symphylids vs^hen infestations are discovered

after the crop has been planted. Apply

it in v^ettable pov^ders or in dusts to the

soil at the rate of 3^4 pounds per acre, or

I ounce per 780 square feet. A convenient dosage is 5 ounces of 25-percent

wettable pov^der or 8 pounds of i-percent dust per 1,000 square feet of surface.

For newly set plants, mix i ounce of a

25-percent wettable powder in 10 gallons

of water and pour i pint of the suspension around the base of each plant. If

preferred, apply the insecticide dry and

water it into the soil. Do not use lindane

in this way, however, except in the greenhouse. When applied to the soil, lindane

imparts a musty flavor to certain root

vegetables. Do not apply lindane to soil

that will be planted later to radishes,

lettuce, endive, or watercress.

Malathion

Aerosols containing 10 percent of malathion are similar to parathion aerosols in

controlling most pests, except that they

have shorter residual toxicity to greenhouse whiteflies and two-spotted spider

mites. Malathion residues can be removed by washing.

Malathion aerosols are safe on greenhouse vegetables when properly applied,

but they may burn the foliage of tomatoes

and cucumbers if temperatures are excessive, especially if the aerosols are applied on a cloudy day and the weather

clears before the ventilators are opened.

The bright sun quickly builds up high

temperatures. Closing the ventilators for

treatment in late afternoon when the sun

is shining may also result in excessive

temperatures. The maximum safe temperature is not known, but it is apparently

85° F. The foliage of rapidly growing

tomato plants is most frequently burned,

the damage usually being confined to

young almost expanded leaves near the

tip. The damage may be general

throughout the greenhouse or localized

where temperatures increase rapidly.

Older leaves are generally unaffected, and

later new growth is normal except for

the weakening effect of the damage on

the plant. To avoid such damage, open

the ventilators quickly when a sudden

rise in temperature and too much sunlight occur. Treat the greenhouse again

if pest control has been poor.

In greenhouses too small for application of aerosols, malathion emulsion

sprays offer a practical means of controlling many pests. They leave no objectionable residue that is not easily removed

by washing. Suitable respirators are

available for those desiring to wear them

when exposed for long periods to the

spray. The usual dosage is 2 teaspoons

of 50-percent emulsifiable concentrate

per gallon of water, or i quart per 100

gallons. Follow the recommendations on

the label. Malathion dusts are not recommended for use in greenhouses.

Metaldehyde

Metaldehyde dusts or readymade baits

will control slugs and snails when properly used. The most effective slug baits

contain metaldehyde mixed with either

calcium arsenate or chlordane. Do not

apply metaldehyde dust or chlordane bait

to vegetables after parts of the plant to

be eaten or marketed appear.

Nicotine

Apply a spray containing 40 percent of

nicotine sulfate to control aphids on

foliage. Use it also as a soil drench to

control fungus gnat larvae. Nicotine is

a violent poison. Follow the directions

and heed all precautions on the container
label. Avoid spilling it on the skin or

getting it into the mouth or eyes.

Parathion

A 10-percent parathion aerosol is used

very extensively in vegetable greenhouses,

because it is efifective against most insect

pests. Because of its long residual action,

parathion is the most effective material

against two-spotted spider mites and

greenhouse whiteflies. Parathion like

malathion aerosols may burn the foliage

of tomato and cucumber plants. Parathion is extremely poisonous and should

be applied only by a trained operator who

will enforce the precautions prescribed by

the manufacturer and assume full responsibility for safety.

Rotenone

Rotenone sprays or dusts are useful for

the control of flea beetles, cucumber

beetles, midges, and several other pests.

They are recommended for the control of

many pests in small greenhouses where

aerosols are impractical. Rotenone is the

active ingredient in derris or cube. Use

a spray containing 4 to 5 pounds of 4-percent rotenone wettable powder per 100

gallons of water, or 4 level tablespoons

per gallon. A i-percent rotenone dust

may also be used.

Sulfur

Dusts containing 25 percent or more

of sulfur are effective against susceptible

species of mites, including the broad,

tomato russet, and white mold mites.

Although pure dusting sulfur is sometimes used, plant injury may result.

TEPP

Aerosols containing 5 percent of TEPP

are useful in the control of aphids, greenhouse whiteflies, and two-spotted spider

mites near harvesttime. However, 2 or 3

days should intervene between application and harvest.

TEPP aerosols are not recommended

for use on tomatoes except those varieties

known to tolerate them, such as Michigan

State Forcing, Grothen's Globe, and June

Pink, because severe burning of foliage

Figure I.—Tomato leaf with small necrotk spots

caused by TEPP aerosols.

may result. Injury is usually not uniform

throughout the greenhouse, apparently

because of local temperature variations.

TEPP aerosols cause necrotic spotting of

leaves on many varieties of tomatoes in

the seedling stage and also on a few

varieties in later stages of growth (fig. i).

Cover flats of young tomato plants of all

varieties with newspaper before releasing

TEPP aerosols. Do not apply TEPP

aerosols to the plants before the first

flower clusters form, as young plants may

be injured. A partially clogged nozzle

discharges large droplets, which cause

necrotic spotting on the young foliage,

particularly of tomato plants. Clean the

nozzle promptly or replace it if it becomes

clogged. TEPP is extremely poisonous

and should be applied only by a trained

operator who will enforce the precautions

prescribed by the manufacturer and assume full responsibility for safety.

GENERAL CONTROL PROGRAM

A well-planned control program can

frequently prevent the development of

damaging populations of insect pests in

succeeding greenhouse crops. After harvesting the crop, destroy the pests on the
old plants in the greenhouse with a heavy

application of parathion. Use parathion

aerosols at twice the standard rate, or 2

pounds of aerosol solution per 50,000

cubic feet of greenhouse space. (See p.

6.) For maximum benefit, close the

ventilators overnight and use the aerosols

before cleaning the greenhouse for the

succeeding crop.

Planting the new crop in a separate

plant house and using every precaution to

prevent contamination from the growing

house will reduce the number of pests.

Keep tomato and cucumber seedlings in

pots for 6 to 10 weeks in a separate plant

house before transferring them to the

growing house. Start lettuce and endive

seedlings in flats or beds and later plant

them in the growing house. Plant radish

and watercress seeds directly in beds of

the growing house. If the new watercress

crop is started by planting sprigs from an

older crop, care should be taken to prevent carrying over any pests. Rid the

other growing-house crops of pests as far

as possible in order to prevent infestations

in the radishes and watercress.

As an added control measure, apply a

parathion aerosol to the new crop at the

standard rate of i pound of aerosol solution per 50,000 cubic feet just before removing the plants from the plant house

or after transferring them to the growing house. Repeat this treatment approximately 4 weeks later and a third

time 2 weeks before the first fruits ripen

or before harvest, even though no insect

pests are evident. These treatments may

prevent pest damage to the plants until

most of the crop is harvested.

Cucumbers are pollinated by hand or

by honey bees to assure a good set of fruit.

Greenhouse tomatoes are usually handpollinated, but recent experiments indicate that honey bees may also be useful in

pollinating tomatoes. When colonies of

honey bees are established in vegetable

greenhouses, screen the entrances to the

hives. Loosely cover the front of the hive

with paper or cloth to protect the bees

from DDT dusts or aerosols when applying them to the crops. Remove the colonies from the range for at least i day when

using TEPP and for 4 or 5 days when

applying malathion or parathion.

Sanitation

A good sanitary program for a commercial greenhouse is important in reducing damage by disease and insect pests.

Do not plant potatoes, tobacco, cucumbers, melons, spinach, celery, and dahlias

close to the greenhouse, since they may

harbor virus diseases and insect carriers.

For the same reason, eliminate milkweed,

plantain, chickweed, catnip, groundcherry, horsenettle, and jimsonweed within 150 feet of the greenhouse. Keep

down all weeds. In the immediate area

of the greenhouse maintain clipped lawn

grass, bare soil, or ground covered with

cinders.

In the greenhouse, cleanup of trash,

including plant debris, eliminates breeding or hiding places of slugs and sowbugs.

Soil Sterilization

To destroy insect pests, such as garden

symphylids, nematodes, and pathogenic

organisms, sterilize the soil by heating it

at 180° F. for 4 hours. Steam is most

universally used for this purpose in vegetable greenhouses.

Before planting the greenhouse crop,

bury drainage tiles in rows about 18 inches

apart and connect them at each end by

crossheads. Introduce steam at 15

pounds' pressure into the crossheads.

Suitable covers of plastic or special paper

over the soil help retain the steam, insure

sterilization of the surface soil, and aid in

getting penetration to the maximum

depth.

Sterilize the soil in raised benches by

introducing steam into the buried tiles or

perforated pipes, and cover these benches

with plastic covers weighted at the edges

to confine the steam.

Sterilize tools, pots, flats, and small lots

of soil in a tightly constructed box of

wood or masonry fitted with a perforated

pipe into which steam is introduced.

If the soil is kept properly moistened

prior to sterilization, the symphylids tend

to congregate near the surface. The heat

from sterilization will then reduce the
populations to such low levels that they

will cause little damage to the succeeding

crop. If the soil is allowed to dry out

prior to sterilization, these pests will penetrate to such depths that the steam will

not reach them and they may return to

cause serious damage to newly set plants.

The treated greenhouse crop may also be

reinfested from outside areas or adjacent

untreated greenhouses through drainage

tiles or gravel drainage layers.

Take every precaution to avoid reinfesting sterilized soil by means of dirty,

contaminated hands, tools, and shoes and

other clothing.

Insecticide Applications

Aerosols

Aerosols that are effective for use on

greenhouse plants usually contain the

poison gas methyl chloride. Only a

trained operator should apply aerosols,

regardless of the insecticidal ingredient.

He should enforce the precautions prescribed by the manufacturer and assume

full responsibility for safety. Wear protective clothing, rubber gloves, and a fullface gas mask with an approved canister

to protect against inhalation and skin

absorption. Avoid contamination of food,

and do not chew or smoke tobacco during

the operation. Change the clothing and

wash the hands and face after completing

the application. Lock or barricade the

entrances and post warning signs during

the treatment period. No one should

enter the greenhouse without wearing a

suitable mask and canister. At the end

of the treatment period, ventilate the

building for i hour before allowing anyone to work in it. Do not use aerosols in

greenhouses connected to living quarters.

Do not apply aerosols when an open flame

is present.

Aerosol cylinders for greenhouse use

contain 4 pounds of the aerosol solution,

which is sufficient for treating 200,000

cubic feet of space, or approximately onehalf acre, in a greenhouse. When the

plants are small and the greenhouses are

tightly closed, reduce the dosage to 2

pounds per 200,000 cubic feet.

Discharge the aerosol into the air above

the plants. Move through the greenhouse at such a speed that the proper

amount will be distributed equally

throughout the area. Avoid overdosage

by treating the greenhouse at the rate of

4 seconds per 1,000 cubic feet of space

with the standard, or 5-gallon-per-hour

oil-burner, nozzle. An area 20 feet wide

can be treated by one person in one trip,

but wider areas require two or more trips,

which can be accomplished best by two

or more operators working together.

Avoid overtreatment at the ends of the

greenhouse. Turn ofi the valve before

the allotted time to allow for the discharge of the aerosol solution in the applicator. In small ranges of 15,000 or 20,000

cubic feet, leave the greenhouse at the end

of the allotted time and discharge outside

any solution left in the applicator.

Best results are obtained with most

aerosols at greenhouse temperatures between 70° and 85° F. Higher temperatures cause plant injury and lower temperatures a poor kill of the pests. Aerosols are sometimes applied on cloudy

days. If the sun appears, excessive temperatures will result, and the ventilators

must be opened promptly. Most growers

apply the aerosols near sunset when the

ventilators can be closed without danger

of a temperature buildup. The aerosolbomb temperature should also be between

70° and 85*^ in order to discharge properly. Store the bomb at the desired temperature for 12 hours prior to use. Do

not increase the temperature of the bomb

by immersing it in hot water, as this is a

dangerous practice. Close the ventilators

before application and keep them closed

for at least 2 hours after treatment and

preferably overnight. The foliage should

be dry during treatment, but the plants

should be well watered.

The aerosol method of applying insecticides has largely replaced dusting

and spraying in commercial greenhouses.

Dusts

DDT dusts are widely used in commercial vegetable greenhouses for controlling corn earworms, tomato pin-
worms, and thrips. (See p. 2.) For

treating large greenhouses, portable

crank dusters or small electric dusters are

most generally used; for small greenhouses, small crank dusters or plungertype dusters are useful. Discharge the

DDT dust into the air above the plants

so that it settles in a light uniform deposit

on the foliage and does not leave excessive residues or cause plant injury.

Rotenone dusts may be used in small

greenhouses for several vegetable pests.

Other insecticides used in dust form include sulfur for certain mites, chlordane

for earwigs outside the greenhouse, and

lindane applied to the soil for garden

symphylids.

Smokes

Combustible powders containing parathion may be obtained in units suitable

for use in different-sized greenhouses.

If the manufacturer's directions are followed, a gas mask is not necessary. Do

not use these smokes in greenhouses

connected to living quarters.

The slow-burning mixture is ignited

with a sparkler. The generated smoke

carries the insecticide throughout the

greenhouse. Since some of the insecticide

is lost or decomposed by the heat, the

dosage for a given space is greater than

for an aerosol. Smokes have less residual

toxicity than aerosols. They are especially useful for the small greenhouse of

10,000 cubic feet or less and should be

used instead of aerosols, because it is

difficult to apply correct dosages with the

latter in small spaces. (Fig. 2.)

Sprays

When applying sprays in the greenhouse, wear a respirator that is approved

for protection against the materials you

are using, or wear the fuUface mask and

canister as for aerosol applications. If the

greenhouse is attached to a dwelling or if

it is too small for the efficient use of aeroFigure 2.—Smoke bomb in operation.

468657° -58-
sols or smokes, apply all insecticides, except DDT, in sprays. Sprays are recommended rather than dusts, because the

insecticide can be directed better toward

the plant. Also it is difficult to avoid

breathing floating dust particles. Compressed-air hand sprayers or small portable power sprayers are suitable for use in

these small greenhouses. In larger greenhouses and ranges, spraying is costly and

not necessary, although portable power

sprayers or stationary spray units have

been used in most commercial greenhouses and are still available in some.

CONTROL IN SMALL

GREENHOUSES

In small greenhouses of 10,000 cubic

feet or less, the following treatments are

recommended. Sprays containing i^

teaspoons of 40-percent nicotine sulfate

and !4 teaspoon of a detergent, such as

Dreft,^ per gallon of water will control

aphids and mealy-bugs. Sprays containing rotenone preparations are effective against greenhouse whiteflies, flea

beetles, cucumber beetles, midges, and

thrips and fairly effective against spider

mites. Use a spray containing 4 to 5

pounds of 4-percent rotenone wettable

powder per 100 gallons of water, or 4

level tablespoons per gallon. A ipercent rotenone dust may also be used.

Sprays containing 2 teaspoons of 50-percent malathion emulsifiable concentrate

per gallon of water are,.also effective

against most of these pests, as well as the

tomato russet, broad, and white mold

mites. Dusts containing 3-percent DDT

or sprays containing 5 level tablespoons

of 25-percent DDT wettable powder per

gallon of water will control thrips, the

greenhouse leaf tier, armyworms, the corn

earworm, and the tomato pinworm.

Light dusting with 25-percent sulfur will

destroy the tomato russet, broad, and

white mold mites.

^ The mention of a trade product does not imply its endorsement by the U. S. Department of

Agriculture over a similar product not named.

INSECT PESTS

Aphids

Four species of aphids, or plant lice, are

commonly found on greenhouse vegetables. They feed on many crops, weeds,

and other plants outdoors. If they become established on greenhouse crops in

the fall, they reproduce continuously

throughout the year. They damage the

plants by their feeding. The melon aphid

and the green peach aphid are particularly responsible for introducing cucumber mosaic into greenhouse tomatoes and

cucumbers. The green peach aphid also

transmits tobacco mosaic. Control of the

aphids and removal of mosaic-infected

plants are important in preventing further spread by insects and by greenhouse

workers.

Foxglove Aph'id

The foxglove aphid is about % inch

long. It is a shining pale green in the

wingless stage and is recognized by the

darker green area around the base of each

(Cornicle, or honey tube. It feeds on

young tomato and cucumber plants and

on lettuce, radishes, and watercress at any

stage, causing yellow spotting and distortion of young leaves (ñg. 3),

Green Peach Aphid

This species is about %o i^^h long, a

pale waxy green in the wingless stage,

and green with a black patch when

winged. It is most common on lettuce,

watercress, and radishes, but it may also

be found on cucumbers and tomatoes.

Heavy infestations cause dwarfing of the

new growth.

Melon Aphid

The melon aphid (fig. 4) is from 14Q

to %5 inch long and varies from pale to

dark green or almost black. It is found

more frequently on cucumbers than on

any other greenhouse vegetable. Several

hundred may occur on the leaves of a

single plant. They cause curling of new

leaves (fig. 5), stunting of tips, and

yellowing and death of older leaves. A

black sooty mold develops on the honey8
TC-5505B and TC-SSOSC

Figure 3.—Tomato foliage injured by the foxglove aphid: Above, curled young tip leaves;

below, yellow feeding spots on older leaf.

dew excreted by the melon aphid. Sooty

mold is seldom observed on plants infested by the three other aphid species.

Potato Aphid

This species is about % inch long and

either pink or green with a frostlike waxy

surface. It feeds in colonies on the veins

and stems of leaves, on tomato blossom

clusters, and on lettuce, watercress, and

radishes. It causes stunting and curling

of new growth.

4: :t ^ * -^

Control: Aphids are readily controlled

with parathion or malathion aerosols or

with nicotine in smokes or sprays, except

Figure 4.—Winged and wingless adults of the

melon aphid.

Figure 5.—Curled cucumber leaves caused by

the melon aphid.

on dense foliage of lettuce or cucumbers,

where TEPP aerosols are more effective.

Usually one application is adequate, but

reinfestations may require later applications. Maintain a safe interval between

the last application and harvest to avoid

excessive residues on each crop. (See

p. 2.)

For control in small greenhouses, see

page 8.

Armyworm

The larvae of the yellow-striped armyworm feed on the foliage of cucumbers,

lettuce, and tomatoes and chew holes in

the side of tomato fruits (fig. 6). The

larvae are found on the underside of

lower leaves, in the fruit, or in ground

cracks. They develop from eggs laid by

adult moths that enter the greenhouse in

the fall.
Figure 6.—Armyworm larva and large gougedout areas In tomato.

Control: Whenever the larvae are observed, promptly apply a malathion or

parathion aerosol or a 3-percent DDT

dust. Avoid undesirable residues by

following the precautions on page 2 for

treating each crop.

For control in small greenhouses, see

page 8.

Beetles

Cucumber Beetles

The striped and spotted cucumber

beetles (fig. 7) are approximately %6

inch long and greenish yellow. The

striped beetle has 3 longitudinal black

stripes and the spotted beetle 12 black

spots on the wings. Both species feed on

many outdoor crops, but especially cucumbers, squash, and dahlias. They

enter the greenhouse in the spring and

fall. While feeding on the tender stems

and flowers of greenhouse cucumbers, the

striped cucumber beetle transmits the

organism that causes bacterial wilt, which

kills the plants.

Control: Because the beetles congregate

on wilting cucumber vines outdoors, a

great many may be destroyed before they

enter the greenhouse by applying DDT

dust to the piles of vine trimmings usually

found near service entrances. Weekly

applications of a parathion aerosol during

the period of the beetles' greatest activity

will destroy those in the greenhouse. In

small greenhouses apply a rotenone dust

or spray. (See p. 8.) Do not apply

DDT to cucumbers within 5 days or

parathion within 15 days before harvest.

TC-3875 and TC-7111

Figure 7.—Above, striped cucumber beetle;

below, spotted cucumber beetle.

Flea Beetles

Three or four species of flea beetles may

attack greenhouse vegetables. The potato

flea beetle (fig. 8) is the most common on

tomatoes. It is a tiny black jumping

insect about %g inch long, which may be

present from May to September. The

adults eat small round holes in the leaves.

10
Figure 8.—Potato flea beetle.

which if severely injured may die. Flea

beedes frequendy cause severe injury to

newly set tomato plants in the field or

garden and occasionally are found on

young plants in pots or flats in the greenhouse.

Control: To control flea beetles in

greenhouses, apply a parathion aerosol or

a I-percent rotenone or 3-percent DDT

dust. Do not apply parathion to tomatoes

within 10 days or DDT within 5 days

before harvest.

For control in small greenhouses, see

page 8.

Cabbage Looper

Moths of the cabbage looper (fig. 9)

enter the greenhouse in the fall. The

pale-green larvae, recognized by their

looping habit when they crawl, may seriously damage lettuce, cucumbers, and

other greenhouse crops before they are

discovered. They are usually found on

the lower leaves, which become ragged

from their feeding.

Control: A parathion, malathion, or

DDT aerosol or a 3-percent DDT dust is

toxic to cabbage loopers. On lettuce a

I-percent rotenone dust is partially effective. Apply it late in the afternoon when

the larvae are active. Observe the preFigure 9.—Larva and adult of the cabbage

looper.

cautions on page 2 to avoid undesirable

residues on the various crops being

treated.

Corn Earworm

The corn earworm (fig. 10), also called

the tomato fruitworm, is often confused

with cutworms and armyworms. The

larvae are green to brown and have alternating light and dark stripes on the sides

of the body. They are less hairy than

cutworms and the coloration is brighter.

Young larvae feed at first on the foliage

of tomatoes (fig. 11) and then enter the

fruit. They damage tomatoes primarily

TC-3851D

Figure 10.—Larva and adult of the corn

earworm.

11
Figure //.—Young corn eärworm larva and feeding injury on tomato leaf.

by eating round holes in the fruits and

devouring the interior (fig. 12). Infestations usually occur in the fall before frost,

when the moths fly into the greenhouse

and lay their eggs.

Control: A parathion aerosol usually

holds this pest in check if applied when

the larvae are small. If the infestation is

heavy, a 3-percent DDT dust will destroy

both large and small larvae. Light infestations may be controlled by handpicking and destroying the infested fruits

and the larvae within. Do not apply

parathion to tomatoes within 10 days or

DDT within 5 days before harvest.

For control in small greenhouses, see

page 8.

Cutworms

Many species of cutworms (fig. 13)

attack a wide variety of plants, including

lettuce, cucumbers, and tomatoes, especially in the seedling stage. They cut off

the plants near the soil surface. Some

species, known as climbing cutworms,

climb older plants and feed on leaves,

buds, or fruits. The most common cutworms attacking greenhouse crops are

the variegated cutworm and the dingy

cutworm (fig. 14). The larvae are j to 2

inches long and greenish or dull gray

with darker markings. They hide in the

soil or mulch during the day and damage

foliage or fruit at night. The larvae develop into night-flying moths. Several

generations may occur in the greenhouse

during a year.

Control: Parathion or malathion aerosols will control cutworms in greenhouses,

particularly when the larvae are small.

A 3-percent DDT dust applied to the soil

surface is also effective. Follow the precautions on page 2 to avoid excessive

residues on each crop.

12
Ë^.

TC-7174 and TC-5456

Figure 12.—Left, corn earworm larva feeding in tomato; right, fruit brealcing down from secondary

rot in damaged area.

on the surface of tender young cucumber

fruits. The latter are deformed as they

expand and are made unattractive by the

scarified areas (fig. 15). The insects hide

by day in the soil, mulch, or dense foliage

of cucumbers and are active by night.

Control: Dust with 5-percent chlordane

to destroy earwigs near the outside of the

greenhouse, but do not apply this material to food crops. Parathion or malathion aerosols will destroy earwigs in the

greenhouse. To avoid excessive residues,

follow the precautions on page 2 for

treating each crop.

Fungus Gnats

Larvae of several species of fungus

gnats (fig. 16) feed on decaying organic

matter in greenhouse soils. They may

injure tomato seedlings growing in flats.

The tiny white larvae, less than '/4 inch

long and with black heads, may feed on

roots or bore into the base of the stem.

The dusky black 2-winged adults,

about Ye, inch long, are observed in flight

or resting on the plants. They do not

feed; only the larvae injure the plants.

Control: Light applications of a 3-percent DDT dust on the plants will control

the adults. To kill the larvae, drench the

soil with I pint per square foot of a solufigure 13.—Larva and adult of the black

cutworm.

TC-3708

Figure 14.—Dingy cutworm larva.

Earwig

The ring-legged earwig, a reddishbrown insect about % inch long with

prominent forceps at the tip of the abdomen, is widely distributed and occasionally damages greenhouse crops. It

feeds on the tender roots of radishes and

13
Figure 15.—Cucumbers iniured by the ringlegged earwig.

TC-4951 and TC-4953

Figure 7 6.—Larva and adult of the fungus gnat.

tion containing i teaspoon of nicotine

sulfate per gallon of water. Do not apply

DDT to tomatoes within 5 days or nicotine within 3 days before harvest.

Garden Fleahopper

The garden fleahopper (fig. 17) sometimes attacks the foliage of greenhouse

tomatoes. This black insect, which is

about %2 inch long, jumps or quickly

moves to the underside of the leaf when

disturbed. It sucks the sap and chlorophyll from the leaves. The feeding punctures appear as small whitish or stippled

areas (fig. 18). When these insects are

abundant, the feeding areas are rather

continuous and the leaves appear gray.

Feeding injury may stunt the growth.

Control: Parathion aerosols control

garden fleahoppers. Nicotine sulfate at

the rate of i teaspoon per gallon of

water, rotenone sprays, or i-percent

rotenone dusts are effective. Do not apTC-7300

Figure 17.—Garden fleahopper adult.

1^

)

''- :'-'7A..

f __

^

>(

figure 18.- —Typical injury by the garden fleahopper on clover leaf.

14
ply parathion to tomatoes within lo days

or nicotine within 3 days before harvest.

Garden Symphylid

The garden symphylid is slender, soft

bodied, and white. It is about J4 inch

long and has 12 pairs of legs and prominent antennae (fig. 19). Although very

frail, it lives for 2 years or more. From

2 to 3 months is required to develop from

egg to adult. The population varies

considerably with the season and with the

temperature and moisture of the soil.

When the soil temperature is low, this

pest is less abundant. When the soil is

moist, it is found near the surface, but

when it is dry, it descends to lower levels,

often below the zone of effective soil

sterilization. It quickly disappears after

exposure when the soil is turned.

The garden symphylid is present in the

loose soil, high in organic matter, that is

found in most greenhouses. When

numerous enough, it seriously damages

Figure 7 9.—Garden symphylid adult. (Courtesy

of Pennsylvania Agricultural Experiment

Station.)

both vegetables and flowers, feeding on

the roots. The damage is most serious on

newly set plants, which seldom die but

fail to grow (fig. 20). Roots of established older plants are also attacked, but

the stunting effect on the later plant

growth is less evident.

Control: To obtain good control in the

greenhouse, water the soil so that the

symphylids come to the surface. Soil

sterilization by the buried-tile method is

the most effective treatment. (See p. 5.)

Survivors below the zone of sterilization

or symphylids coming from outdoors may

TC-3741

Figure 20.—Left, normal lettuce plant; right, injury caused by the garden symphylid.

15
injure the plants after they are set. Lindane can then be used by treating individual plants if only a few are affected or the

entire greenhouse if the infestation is

general. Follow the instructions under

Lindane on page 3.

Greenhouse Leaf Tier

The greenhouse leaf tier larva is pale

green and about % inch long. The adult

is a light-brown moth about the same

length and has wedge-shaped flat wings

when at rest. It lays its eggs on foliage at

night. It may be flushed from dense

foliage during the day. This insect is an

occasional pest on tomato plants, where

each larva ties several leaves together.

Infestations may originate on nearby

chrysanthemums, snapdragons, and related plants. In the South this insect is a

pest of outdoor crops, but in the North it

survives the winter only in the greenhouse. It has become rare in northern

greenhouses where parathion or DDT is

used regularly.

Control: Destroy leaf tier larvae and

adults with two applications of a parathion aerosol or a DDT aerosol or dust.

Do not apply parathion to tomatoes within 10 days or DDT within 5 days before

harvest.

For control in small greenhouses, see

page 8.

Greenhouse Whitefly

The triangular adults of the greenhouse

whitefly (fig. 21) are about %g inch long

and have powdery white wings. They

appear as snowflakes when flushed from

infested plants. Their cone-shaped eggs

hatch in 5 to 6 days, and the stationary

yellowish-green young feed for about 5

weeks before becoming adults. The

adults begin laying eggs about 5 days

after emergence. Their life history must

be considered in carrying out a successful

control program.

Figure 21.—Nymphs and adults of the greenhouse whitefly.

Greeson-70,126

(Enlarged.)

16
The greenhouse whitefly is a common

pest on greenhouse cucumbers and tomatoes and is less common on lettuce.

It also infests many ornamental plants

throughout the country, both in the greenhouse and outdoors. The insect breeds

on vegetables in the field, including

squash, potatoes, and tomatoes, during

the summer and often reinfests greenhouse crops in the fall. It does not survive the winter outdoors in cold climates.

Whiteflies suck the juices from the

underside of the leaf (fig. 22). Foliage

of infested plants becomes yellowish

Figure 22.—Greenhouse whiteflies and blacit parasites on tomato leaf.

17
green, and the plants are stunted. Foliage

and fruits are often blackened by the

sooty fungus that grows on the honeydew

excreted by the insects. Whitefîies are

reduced but usually not satisfactorily controlled by parasites.

Control: Use an aerosol containing

parathion, TEPP, or malathion. Apply

the parathion aerosol 2 or 3 times at intervals of 2 weeks until the infestation is

destroyed. Use the TEPP aerosol every

5 days for 4 to 5 weeks to destroy the

newly emerged adults before they start

laying eggs. Eggs and nymphs are not

affected by TEPP. Use 4 weekly applications of the malathion aerosol to destroy

the adults. It will kill some of the larvae,

but it is most effective against the adults.

Follow the precautions on page 2 when

using these insecticides.

For control in small greenhouses, see

page 8.

Mealybugs

Localized infestations of the citrus (fig.

23) or grape mealybug on cucumbers and

tomatoes become serious late in the

season. They can usually be traced to

infested ornamental plants brought into

the greenhouse as boarders. Grape

mealybugs are found on roots of shrubs

and trees. They may crawl into the

greenhouse or may be brought in by ants.

Mealybug infestations are recognized by

the cottony masses on the stems and leaves

and by the black sooty mold that grows

on the honeydew excreted by these pests

(fig. 24).

Control: When the infestation is confined to a few plants, remove and destroy

the affected plants. When the infestation

is more general, apply a parathion, malathion, or TEPP aerosol three or more

^^^L^ ,^^^^^^^^^^^^V ^^^^^k

Figure 23.—Citrus mealybugs.

Figure 24.—Cucumber fruit and stem infested

with the citrus mealybug.

times at lo- to 14-day intervals. To avoid

excessive residues on each crop, follow the

precautions on page 2.

For control in small greenhouses, see

page 8.

Mites

Broad Mite

The broad mite, seen only with a microscope, is an outdoor pest of many plants

in the warmer areas of the United States.

It is brought into northern greenhouses

on ornamental plants from the South,

where it breeds throughout the year and

damages many kinds of ornamentals and

vegetables, including tomatoes and cucumbers. The tiny caramel-colored mites

feed on the lower surface of young leaves.

Injured leaves become stiff and brittle,

are cupped downward, and develop a

mottled and glazed appearance that resembles a virus disease.

Control: To destroy broad mites, use a

parathion aerosol or two light applications, a week apart, of a dust containing

25 percent or more of sulfur. Do not

apply parathion to tomatoes within 10

days or to cucumbers within 15 days before harvest.

For control in small greenhouses, see

page 8.

18
Mushroom Mite

The mushroom mite is a slow-moving

species about %o ^^^^ ^^^§ ^^^ has a

white rounded body and long bristles. It

is frequently found on rotting compost

and may be brought into the greenhouse

with the manure mulch. As the mulch

dries, these mites move to nearby plants

and gouge out small pits in the stems and

leaves of cucumbers. Tender young

plants are more susceptible to attack than

older plants. The period of damage is

usually short, because the mites do not

normally subsist on living plant tissue.

Control: When damage is observed,

promptly apply a parathion or TEPP

aerosol. Do not apply parathion to cucumbers within 15 days or TEPP within

3 days before harvest.

Tomato Russet Mîte

This slow-moving mite, visible only

under high magnification, is milky white,

cylindrical, and wedge shaped, tapering

toward the posterior end. It is an outdoor

pest of tomatoes in warmer sections of the

country and is sometimes brought to

northern areas on young plants. Once

established in a greenhouse this mite may

be taken to the field with infested plants,

where it damages the crop, and it may

reenter the greenhouse on the fall crop.

This microscopic mite may complete a

generation within a week, and consequently its damage increases rapidly. In

feeding, it causes the main stem to become rusty brown, and the foliage becomes papery and dies. Infested fruits

also are russeted and sometimes cracked.

Control: A parathion aerosol or a 25-

percent sulfur dust applied at 2-week

intervals is effective in controlling the

tomato russet mite. Do not apply parathion to tomatoes within 10 days before

harvest.

For control in small greenhouses, see

page 8.

Two-Spotted Spider Mite

The two-spotted spider mite (fig. 25)

is the most troublesome pest of greenhouse tomatoes and cucumbers. It may

also attack radishes, lettuce, and other

crops.

These mites are found on outdoor

weeds or other plants. They crawl or are

carried by the wind or by workers on

their clothing or tools to the indoor crops.

Outdoors the adults hibernate on lowgrowing vegetation, but in the greenhouse they reproduce continuously. Under a hand lens the adults appear green

or reddish with a dark spot on each side

and are about %o ii^^h in length. They

deposit shining globular eggs on the

underside of the leaf, and the young

hatch in a few days. Since a generation

may develop in 9 days in a warm greenhouse, a mite population builds up rapidly. At lower temperatures the development is much slower.

The mites feed on the undersurface of

the leaf. Injured leaves have a white

stippled appearance, which is due to a

loss of chlorophyll. More serious injury

results in a yellowed or bronzed appearance, and the leaves tend to curl and dry

out. Such infested plants become covered

with webs and are stunted or even killed.

Usually the injury is most severe during

the fruiting period, when the fruits may

be reduced in size and the harvest period

shortened considerably (fig. 26).

Control: A parathion aerosol is effective

in controlling the two-spotted spider mite.

Use it as a preventive measure in the

plant house and also apply it two or more

times in the growing house before harvest.

Figure 25.—Adult female of the two-spotted

spider mite.

19
TC-5452A and TC-5452B

Figure 26.—Left, normal tomato fruit and leaf; right, injury caused by tlie two-spotted spider mite.

Control an established infestation with

2 or 3 applications at 7- to lo-day intervals.

During the fruiting period when a

parathion aerosol might leave an undesirable residue, apply a TEPP aerosol at

5-day intervals until the mites are controlled, but do not apply it within 3 days

before harvest. A malathion aerosol may

also be used at 5- to lo-day intervals on

tomatoes. Do not apply it to tomatoes

within 15 hours, to cucumbers within i

day, or to leafy vegetables within 10 days

before harvest.

Parathion-resistant strains of spider

mites have not appeared in vegetable

greenhouses as they have on greenhouse

roses, chrysanthemums, and other ornamental crops. To prevent their development on vegetable crops, clean out the

greenhouse and destroy all plant materials

remaining after harvest, especially ornamentals. Destroy all outdoor crops or

20
weeds that might serve as reservoirs of

mite infestations for the succeeding greenhouse crop.

For control in small greenhouses, see

page 8.

White Mold Mite

The white mold mite is similar in

structure and size to the tomato russet

mite, but it causes an abnormally heavy

growth of white hairs on the stems and

leaves of tomato plants. It has been

found occasionally in northern greenhouses and was doubtlessly introduced

from the warmer regions of the country.

Control: A thorough cleanup of crop

remnants and applications of a 25-percent

sulfur dust or a parathion aerosol will

control the white mold mite. Do not

apply parathion to tomatoes within 10

days before harvest.

For control in small greenhouses, see

page 8.

Slugs and Snails

The presence of slugs (fig. 27) and

snails is revealed by their track of slime

as well as their feeding injury. The

foliage of lettuce and watercress is damaged at any stage of growth. The tomato

fruit (fig. 28) is most likely to be injured

when the plants are lowered on the suj)-

porting strings and a cluster of fruit

touches the mulch. These pests hide by

day in damp places beneath the rim of

pots, in bench or wall cracks, benchboards,

or flats beneath the bench. They tend to

come out when the humidity is high.

Slugs may not feed every night but may

hide for several nights between feedings.

For this reason a single application of bait

may be ineffective.

Control: Slugs and snails enter the

greenhouse through cracks in the walls

and through the side ventilators that remain open. Much can be done to eliminate outdoor sources. Reduce the dampness near the greenhouse as much as possible. Keep the grass and weeds cut to

reduce the hiding places of these pests.

Do not leave piles of manure, soil, or

compost near the greenhouse. Do not

store pots, flats, pipe, or other equipment

TC-238

Figure 27.—Spotted garden slug.

rC-5448

Figure 28.—Tomato injured by slugs.

in damp places near the greenhouse or

under the benches. Sterilize the soil and

potting mixtures before they are brought

into the greenhouse. Where conditions

favoring the existence of the slugs and

snails cannot be eliminated, use baits

periodically.

Effective granulated and pelleted metaldehyde baits are available commercially.

Sometimes they contain 2 percent of calcium arsenate or 5 percent of chlordane.

Sprinkle the bait between the plants or

place about a teaspoonful in a pile ar

intervals of 3 or 4 feet.

A 10- to 15-percent metaldehyde dust

is generally effective, but it is more costly

than baits. Apply it to the soil at the rate

of I pound per 1,000 square feet. A dust

may also be spread in a band over which

slugs must cross to reach their feeding

area; thereby less material is required

than when the entire area is treated.

The effectiveness of metaldehyde baits

and dusts varies under different conditions. Metaldehyde causes temporary

paralysis of slugs and snails. Under

warm, dry conditions these affected in21
dividuals rapidly dehydrate and die.

Under cool, moist conditions they may

recover from the paralyzing efiect, especially if they have eaten too little to be

killed, and continue the infestation. The

calcium arsenate increases the efiectiveness of the bait against paralyzed slugs,

particularly under unfavorable conditions. Follow a regular schedule of bait

applications until the pests are eradicated.

Avoid getting the bait on the foliage.

Do not apply metaldehyde dusts to vegetables after the parts of the plant to be

eaten or marketed appear.

Sowbugs

Two species of sowbugs are commonly

found in greenhouses. They usually feed

on decaying organic matter, but they may

also attack seedling plants and damage

the main stem of tomato plants at the soil

surface.

Sowbugs (fig. 29) are about K inch

long and gray and have transverse overlapping plates covering their backs.

When disturbed, one species rolls into a

ball with the plates outside. It is sometimes called a pillbug. Sowbugs and pillbugs feed at night or on cloudy days and

hide during the day in damp places under

pots, boards, or trash.

Control: A 3-percent DDT dust or a

parathion aerosol is effective in controlling

sowbugs. Make two applications of a

parathion aerosol at lo-day intervals, or

use it until the pest is eradicated. Avoid

excessive residues by following the precautions on page 2.

Thrips

Greenhouse Thrips

The adults of this species are about

%Q inch long and dark brown and have

a lighter median band (ñg, 30). The

larvae are milky white and carry an accumulation of dark excrement on their

backs. Both the adults and larvae cause

a coarse stippling of the foliage. This

species is usually brought into vegetable

greenhouses on house plants or other

ornamentals. It does not survive outdoors

in the Northern States.

Figure 29,—Sowbug adult.

TC-S659

Figure 30,—Greenhouse thrips adult.

Onion Thrips

A common pest of greenhouse cucumbers and tomatoes is the onion thrips.

The highest populations occur on cucumbers; as many as 300 larvae and adults

have been collected from one plant. This

insect is slender, light brown, and about

1^5 inch long. The larvae are milky

white when young but pale green to

lemon yellow when nearly mature. Both

larvae and adults feed by rasping the leaf

surface and lapping up the exuding

juices. White stippled areas appear on

the upper leaf surface (fig. 31), and the

lower surface becomes shiny. When die

injury is severe, the leaves turn brown and

die and the plants become dwarfed or die.

The onion thrips transmits the virus

that causes spotted wilt to greenhouse

tomatoes from outdoor dahlias and other

infected host plants. In the fall the in22
Figure 3 J.—Feeding injury by the onion thrips

on cucumber foliage.

sects move into the greenhouse bringing

with them the virus, which, if uncontrolled, may infect a large percentage of

the plants.

^ !t( « )|C «

Control: A parathion, malathion, or

DDT aerosol or a 3-percent DDT dust

will control these two species of thrips.

Make 2 or 3 applications at lo-day intervals to destroy an infestation. After

onion thrips are controlled with DDT,

spotted wilt stops spreading. Prevent

excessive residues by following the precautions on page 2.

For control in small greenhouses, see

page 8.

Tomato Pinworm

The grayish-purple larvae of the

tomato pinworm (fig. 32) are about '/4

inch long. They bore into the stems, mine

the leaves (fig. 33), and tunnel in the

fruits near the stems (fig. 34). Pinworms

originating from greenhouse infestations

may persist during the summer on tomatoes, potatoes, eggplants, and horsenettle in the field and return to the fall

crop of tomatoes in the greenhouse.

Although this insect does not survive outdoors in the North, occasionally it becomes established on tomatoes in northern greenhouses. It is common in California.

Control: Omitting the fall crop of

greenhouse tomatoes will eliminate the

Figure 32.—Larvae and adult of the tomato

pinworm.

Figure 33.—Leaf-mining injury by the tomato

pinworm.

infestation. A parathion aerosol or a

3-percent DDT dust applied at 2-week

intervals has eliminated serious infestations in northern greenhouses. Do not

23
fested soil that is brought in from the

field and not sterilized.

Control: Steam sterilization of soil before planting will destroy any wireworms

present. If the soil is not sterilized, mix

8 ounces of 50-percent chlordane wettable

powder in 50 gallons of water and apply

'/4 pint in the holes when the plants are

set, or apply the mixture to the entire area

to be planted at the rate of 300 gallons

per acre and work into the soil. Do not

apply chlordane to plants after the edible

parts appear.

Figure 34.—Tomato damaged by the tomato

pinworm.

apply parathion to tomatoes within 10

days or DDT within 5 days before harvest.

For control in small greenhouses, see

page 8.

Wireworms

Wireworms are the larvae of several

species of click beetles. They are shiny,

slender, and cylindrical. Their yellowish-brown hard bodies are '/i to i !4 inches

long. Wireworms feed on the underground parts of many crops. They devour seeds in the soil, cut off small roots,

and bore into larger roots and stems

(fig. 35), causing severe crop losses.

Wireworms may damage greenhouse

vegetables when they are grown in inFigure 35.—Left, lettuce stems and roots injured

by the wireworm; right, wireworm larva.

24
COMMON AND SCIENTIFIC NAMES OF INSECT PESTS

OF GREENHOUSE VEGETABLES

Common name Scientific name

- ^ Armyworm Pseudaletia unipuncta (Haw.)

-- • Black cutworm Agrotis ypsilon (Rott.)

Broad mite Hemitarsonemus latus (Banks)

" / Cabbage looper Trichoplusia ni (Hbn.)

- * Citrus mealybug Pseudococcus citri (Risso)

-^ Vu Corn earworm Heliothis zea (Boddie)

- ' Dingy cutworm Feltia subgothica (Haw.)

_ ^ Foxglove aphid Myzus solani (Kltb.)

s<- - * Fungus gnat Lycoria inconstans (Fitch)

- * Garden fleahopper Haïtiens bracteatus (Say)

^"^ Garden symphylid Scutigerella immaculata (Newp.)

^ Grape mealybug Pseudococcus maritimus (Ehrh.)

^ Green peach aphid Myzus persicae (Sulz.)

^ Greenhouse leaf tier JJdea rubigalis (Guen.)

— " Greenhouse thrips Heliothrips haemorrhoidalis (Bouché)

" * Greenhouse whitefly Trialeurodes vaporariorum (Westw.)

< * Melon aphid Aphis gossypii Glov.

~ Mushroom mite Tyrophagus lintneri (Osb.)

^ * Onion thrips Thrips tabaci Lind.

~ Potato aphid Macrosiphum solanifolii (Ashm.)

^ * Potato flea beetle Epitrix cucumeris (Harr.)

- < Ring-legged earwig Euborellia annulipes (Lucas)

-"X * Sowbug or pillbug Armadillidium vulgäre (Latr.)

-- ^ Spotted cucumber beetle Diabrotica undecimpunctata howardi

Barber

— - Spotted garden slug Umax maximus L.

^ ' Striped cucumber beetle Acalymma vittata (F.)

-- ^ Tomato pinworm Keijeria lycopersicella (Busck)

— Tomato russet mite Vasates lycopersici (Massée)

- ^Two-spotted spider mite Tetranychus telarius (L.)

-- Variegated cutworm Peridroma margaritosa (Haw.)

-- X White mold mite Eriophyes cladophthirus Nalepa

- y " Wireworms Melanotus spp.

._. Yellow-striped armyworm Prodenia ornithogalli Guen.

IS

U. S. GOVERNMENT PRINTING OFFICE: I9S9