Aphids on tobacco : how to control them

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a JUNG = 1960” y

4 &. S. DEPARTMENT OF Acme ORME

LEAFLET NO. 405

UNITED STATES DEPARTMENT OF AGRICULTURE

By F. R. Lawson and F.S. CoamBertiin, Entomology Research Division,
Agricultural Research Service

Aphids are pests of tobacco
wherever the crop is grown in the
United States. They injure the
growing tobacco leaves and may
spread tobacco virus diseases.

The aphid that attacks tobacco
is the green peach aphid.t Among
tobacco growers it 1s commonly
known as the tobacco aphid or
tobacco louse. It is a soft-bodied,
sucking insect about the size of a
cabbage seed. It can be controlled
by applying insecticides or, in
some areas, by cultural practices.

LIFE CYCLE OF APHIDS

in Southern States

In the Southern States the
aphids are nearly all females. The
adults deposit their young, which

BN-2163

Green peach aphid, wingless form: Nymph,
almost grown.

are called nymphs, on various
host plants. Most of the nymphs
develop into green, wingless
adults, which in turn produce
another generation of wingless

1Myzus persicae (Sulz.).

females. The adults and nymphs
of the wingless form look alike.
The other nymphs develop into
blackish, winged adults.
Successive generations of fe-
males, mainly wingless, are pro-

BN-2165

BN-2164

Green peach aphid, winged form: Above, adult;
below, nymph.

duced throughout the year. This
pattern of development is preva-
lent as far north as Tennessee
and Maryland.

The host plants in the fall,
winter, and early spring are cab-
bage, collard, turnip, wild mus-
tards, and dock. In the spring,
winged aphids fly to tobacco.

in Colder Climates

In the colder climates, a gen-
eration of males and egg-laying
females develops in the fall. The
eggs are laid mostly on peach,
wild plum, and wild cherry trees;

BN-2077

Foreground, shade-grown tobacco stunted by aphid feeding; background, tobacco protected by
insecticides.

they are green at first but soon
turn shiny black. It is only in the
egg stage that the aphids survive
subzero temperatures. The eggs
hatch in the spring. Usually, the
second or third spring genera-
tion infests tobacco.

DAMAGE TO TOBACCO

Aphids damage the _ tobacco
plant by sucking the juices from
the leaves. When aphids are
abundant the plants become
stunted. Leaves from these plants
are thin and lifeless when cured.
A severely damaged leaf may die
or may ripen prematurely.

Aphids contaminate tobacco by
depositing cast skins and an ex-
cretion, known as honeydew, on
the leaves. Honeydew causes the
leaves to stick together, and it
cannot be removed from the har-
vested leaves without damaging
them. It mildews in wet weather
and gives the leaves a blackish
appearance.

Aphid damage quickly ruins a
cigar-wrapper tobacco crop, be-
cause imperfect leaves cannot be
used as wrappers. Other types of
tobacco usually are not ruined,
but their quality and yield are
reduced. On types of tobacco that
are harvested by cutting the

whole plant, such as Maryland,
the yield and quality may be re-
duced by premature ripening of
the lower leaves.

INFESTATIONS
How They Start

Aphid infestations in tobacco
may start in the plant bed or in
the field, depending on the condi-
tion of the winter and spring host
plants.

In the Connecticut River Valley
area, aphids normally spend the
winter in the egg stage. During
the spring season winged forms
are produced and fly to other food
plants. They may infest tobacco
plant beds and fields.

In Tennessee and Kentucky, few
aphids survive the winter. Plant
beds of burley and dark fire-cured
tobaccos usually are not infested
by aphids from the local winter
host plants, but they may be in-
fested lightly in May by winged
aphids from other areas. Field
infestations early in the season
are light also, and the aphids do
little damage before the plants
are topped.

In central and northern North
Carolina and in southern Virginia,
most of the aphids spend the fall
and winter on garden patches of
collards and turnips. A plant bed
near these patches usually will be
infested. Under the cover, where
it is warm, the aphids multiply
rapidly. They are carried to the
tobacco field on the seedlings.
Most of the heavy infestations in
the field are started in this way.

In South Carolina and southern
North Carolina, aphids winter on
garden patches, as they do in cen-
tral and northern North Carolina
and in southern Virginia, and
they start some plant bed infesta-
tions. In these areas, however,
most of the aphids that infest
tobacco come from extensive

growths of wild mustard in grain
and clover fields and in pastures.
Large numbers of aphids feed on
the mustard in late winter and
spring. The mustard matures
about the time that tobacco is set
and many tobacco fields are in-
fested by aphids flying from the
mustard, especially when tobacco
is planted near mustard.

In Florida and Georgia, both
plant beds and fields may be
heavily infested by aphids flying
from fields of wild mustard or
cultivated greens.

How They Develop

Aphids reproduce quickly on
young tobacco in the field, espe-
cially in the shade. They are most
numerous on the underside of the
lower leaves of tobacco plants, but
a great many may be found also
on the youngest leaves near the
tip of the plant. When they are
abundant, they cover almost all
the leaves.

In Virginia, the Carolinas, Geor-
gia, and Florida, they increase
rapidly for a month or more in
the field, but they do not thrive
after hot weather begins. When
the temperature reaches 90° F.
3 or 4 days in succession, large
numbers of aphids die and turn
black. Some may remain in shady
spots, but few are seen elsewhere
unless the weather becomes cool.
When aphids infest the plant beds
early or where large numbers of
aphids fly into tobacco from mus-
tard fields, they may become
abundant enough to injure the
plants before hot weather begins.
Unshaded fields that are lightly
infested early in the season are
not likely to be injured unless
weather conditions are especially
favorable for aphid development.
On cigar-wrapper tobacco, which
is grown in the shade, aphids in-
crease so rapidly that damage
may occur at any time.

A leaf of flue-cured tobacco damaged by aphids.

BN-2076

Part of the leaf is black from mildew growing

on the honeydew excretion.

In Tennessee, Maryland, and
the Northern States, the aphids
may increase all summer, and
most of the damage occurs late in
the season. In warm weather they
may reproduce so rapidly on the

lower leaves that severe damage
occurs before the grower notices
them. When the temperature is
higher than 95° F. for several
days, many aphids die, and danger
of severe injury is reduced.

CULTURAL PRACTICES

Many of the worst aphid infes-
tations on tobacco are started in
the plant beds by aphids moving
from nearby patches of collard,
turnip, mustard, or dock. Beds
should be located a safe distance
from such sources of aphids, or
the winter host plants should be
destroyed before the tobacco ger-
minates. If this is not done the
beds may be reinfested even if
they are treated with insecticides.
The removal of winter hosts is an
effective way to prevent heavy
infestations in the field.

The tobacco field should be free
of weeds before the plants are set.

INSECTICIDE TREATMENT

Malathion, thiodan and parathi-
on are effective insecticides for
controlling aphids. Malathion and
thiodan are less hazardous to ap-
ply. The insecticides can be used
as dusts or sprays.

Selection
DUSTS

If “you “preter Sdusts.. buy. 2
ready-to-use dust containing 4
percent of malathion or thiodan or
1 percent of parathion.

SPRAYS

For hand equipment, which is
used in plant beds, and high-
gallonage (50 to 100 gallons per
acre) equipment, which is used
in the field, buy an emulsifiable
concentrate or a wettable powder
that contains malathion or para-
thion. The amount to mix with 100
gallons of water is shown below.

MALATHION—2 pints of 50-
percent emulsifiable concentrate
or 4 pounds of 25-percent wet-
table powder.

PARATHION—1 pint of 25-per-
cent emulsifiable concentrate or
1 pound of 15-percent wettable
powder.

For aircraft sprayers or other
low-gallonage (1 to 5 gallons per
acre) equipment, buy an emul-
sifiable concentrate that contains
malathion or parathion. Wettable
powders are not suitable; they
tend to clog the nozzles. Mix the
emulsifiable concentrate with 1 to
5 gallons of water. (The amount
of water to use depends on the
capacity of the equipment.) Use
an amount of the concentrate that
will give 15 pound of parathion
(actual) or 1 pound of malathion
(actual) per acre.

Application

The insecticide should be ap-
plied to the plants thoroughly but
lightly. The dosage depends on
the size of the plants. Quantities
larger than those recommended
increase the cost of treatment and
the hazard of excess residues on
the tobacco.

If you use a spray, apply it im-
mediately after it has been mixed.

IN PLANT BEDS

All cigar-wrapper tobacco plant
beds should be treated several
times with an insecticide, whether
or not aphids are found. Other
tobacco plant beds should be in-
spected from time to time and
treated as needed. It is also a good
plan to treat any infested beds a
few days before the plants are
transplanted to the field.

The rate of application for dust
is 1 pound per 100 square yards;
for spray, 5 gallons per 100 square
yards. You can apply dust with-
out removing the plant bed cover,
provided the cover is dry and is
not touching the plants.

IN THE FIELD

Cigar-wrapper tobacco plants
should be treated in the field once
a week for the first 6 weeks. As
the tobacco matures, it should be
searched often for aphids. Small

Horse-drawn traction sprayer equipped with a protective shield.

yl

(== a= /= —-=_——e 4

BN-2078

Operator must wear a mask

and protective clothing when applying parathion.

outbreaks may be spot treated
with a hand duster. During the
last part of the growing season
this tobacco should be treated by
aircratt.

The plants of other tobaccos
should be inspected carefully be-
fore they are a foot high. If only
scattered aphids are found, treat-
ment may not be necessary. If
the smallest leaves of numerous
plants are infested, an insecticide
should be applied. Plants growing
in the shade may need treatment
when those in the sun do not. The
timely use of insecticides in the
plant bed and on young plants in
the field will reduce the chances of
severe infestations later in the
season.

If ground equipment is used,
the rates of application are as
follows:

Dust—8 to 15 pounds per acre
on small plants; 20 to 30 pounds
per acre on large plants.

SPRAY—50 to 60 gallons per
acre on small plants; 75 to 100
gallons per acre on large plants.

If aircraft is used, the rates of
application are as follows:

DusT—20 to 380 pounds per
acre.

SPRAY—1 to 5 gallons per acre.
c)

Control of Other Insects
Occurring With Aphids

The tobacco hornworm, the
tomato hornworm, budworms, flea
beetles, and climbing cutworms
may occur with aphids in the

same tobacco field. It is not pos-
sible to control all these insects
with any single insecticide, but
two or more insecticides may be
included in the same dust or spray.
TDE, DDT, or endrin will control
budworms and climbing cut-
worms. TDE or endrin will also
control hornworms,
endrin will control flea beetles.

SPRAYS

Combination sprays can bé pre-
pared by adding to the parathion
or malathion sprays described on
page 6 a sufficient amount of an
emulsifiable concentrate of TDE,
DDT, or endrin to make 1 pound
of TDE, 14 pound of DDT, or 14
pound of endrin per acre.

DUSTS

Effective combination dusts
should contain—

1 percent of parathion or 4 per-
cent of malathion or thiodan; and

10 percent of TDE or 10 per-
cent of: DDT.

If a combination dust is applied
to the buds of the plants, it should
be used lightly because a heavy
dosage is likely to cause plant
damage, especially if the plants
are wet.

©

PRECAUTIONS

The insecticides mentioned in
this leaflet are poisons. Store
them where children and animals
cannot reach them. Handle them
with care. Follow the directions
and heed all precautions on the
container label. Use the recom-

Washington, D.C.

and DDT:or

mended protective equipment to
avoid personal exposure.

Do not apply malathion within 3
days or thiodan within 5 days be-
fore a priming or cutting.

Parathion and endrin are espe-

~clally dangerous, and may cause

death .when- inhaled, absorbed
through’ the skin, or swallowed.
They should be used only by
trained operators who will assume
full responsibility for safe use and

comply with all the precautions

prescribed by the manufacturer.
Do not apply parathion or endrin
within 5 days before priming or
15 days before cutting.

Avoid getting parathion or en-
drin on the skin. Keep them away
from the eyes, nose, and mouth.
Wear a respirator of a type that
has been tested by the U.S. De-
partment of Agriculture and
found to be satisfactory for pro-
tection against the particular in-
secticides you are using. Wear
rubber gloves and_ protective
clothing. When using a hand dust-
er, arrange the discharge tube so
that it extends backward behind
you. Watch the wind direction and
stay out of the dust cloud. If you
use a walking traction sprayer,
use one that is equipped with a
protective shield. Wash your
hands and face thoroughly before
eating or smoking. Bathe after
working with these materials and
wash your clothing before wear-
ing it again.

if you must transplant or other-
wise handle plants within 5 days
after treatment with endrin or
parathion, protect your skin by
wearing clean, dry, cotton gloves
or a good grade of rubber gloves
and tightly woven clothing.

Issued January 1957
Slightly revised April 1960

U.S. GOVERNMENT PRINTING OFFICE: 1960

For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington 25, D.C. - Price 5 cents

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