McWhorter, Mike

Texas A&M University

L-1417
INSECT AND MITE PESTS OF FIELD CORN
G. Mike McWhorter
Extension Entomologist
The Texas A&M University System
Life Cycle
The southwestern corn borer overwinters as a
full-grown larvae and usually hibernates at or near
the base of the plant crown. The hibernation site
is in a "tunneled out" area wi thin the plant. The
upper part of the tunnel is clo ed with a tough
silken plug for protection. In the spring the borer
extends its tunnel to the outer wall of the crown,
leaving a thin covering which the moth can easily
push aside. Pupation then follow, and the moth
soon emerges from the tub of the stalk. Mating
occurs within a couple of days and eggs are glued
to the plant, usually on the top side of a leaf about
half way up the stalk. The eggs hatch within a
few days, depending on the temperature.
generally average four or five per group. The color
and appearance of the eggs change as the incuba-
tion period progresses. Three parallel rows of red-
dish-orange lines appear prior to hatching, and the
color changes to yellow, orange-yellow or reddish-
brown before hatching.
After the egg hatch, the small larvae closely
resemble the full grown "worm," which is from I
to I Y4 inches long and dull white or yellowi h-
white in color. The larvae also have a regular pat-
tern of dark brown polka dot which generally di -
appears in the creamy yellow overwintering form.
The mahogany brown pupae are slightly shorter
than the larvae. They are normally found within
the corn stalk during the summer, and in the crown
of the plant just below the oil surface in the
spnng.
The moths are from 3/5 to 3/4 inch long with
a wing spread of I Y4 inches. They are solid white
to pale yellow and fold the wings about the body
when at rest. A characteristic snout extends from
the head.
Corn acreage in Texa is increasing. Irrigated
corn acreage increa ed from 602,000 acres in 1966
to more than 1,100,000 acres in 1975. Therefore,
corn in ect pest control is becoming increasingly
important.
V\ ith the expansion of an agricultural crop,
insect and mite pests and their damage generally
also increa e. Al though use of pesticides cannot
be eliminated, every effort must be made to use
them in an economical and scientifically sound
manner. Along with u ing the lowest possible effec-
tive dosage of pe ticide, and using them only
when needed, other important control procedures
include variou cultural practices, biological con-
trol method and planting resistant varieties. The
development of re i tant or tolerant varieties may
hold the greate t promi e for corn insect control
in the future. In any case, an effective pest control
program is an integrated program based on cul-
tural and mechanical practices as well as the use
of pe ticide .
umerous arthropods (insects and mites), both
harmful and beneficial, are commonly found in
corn. But only the southwestern corn borer and
certain spider mites (primarily the Banks grass mite)
are of major concern at this time.
Southwestern Corn Borer
The southwestern corn borer was first found in
the United States in 1913. It spread north and east
from Mexico into the Texas Panhandle, and was
e tablished in Colorado, Kansas and Oklahoma by
1931. It has become the major pest in irrigated
corn growing regions of Texas, especially in the
High Plains.
Description
The egg are elliptical to oval, flattened, slightly
convex on the upper surface, and translucent white
when fir t laid. They are quite small and average
1.2 to 1.6 mm in length by 0.8 to I mm in width.
The borer lay its eggs in chains or groups that
overlap much like fi h scales or roof shingles. Eggs
may be found in groups of two to 50 or more, but
19.12
Stage
Egg
Larva
Pupa
Adult
Developmental Periods
Average no. of days
5
25
10
5
Texas Agricultural Extension Service • The Texas A&M University System • H. O. Kunkel, Acting Director • College Station
SEASONAL HISTORY
CORN BORER ON
OF THE SOUTHWESTERN
TEXAS HIGH PLAINS
INDICATES TIME FIELDS
SHOULD BE SCOUTED TO
DETERMINE NEED TO CONTROL
SOUTHWESTERN CORN BORER.
APRIL
15
MAY
15
DIAPAUSING
JUNE
15
JULY
15
AUGUST
·,'1' ." .: .. ·· .. :,:'15:::::;:
"":.
SEPTEMBER
15
OCT-MARCH
Control
Cultural practices play a critical role in man-
aging the southwestern corn borer. Fall or winter
stalk destruction through double disking, chiseling
and deep breaking destroys the plant crown and
increases overwintering larval mortality.
When stalks are grazed out, some type of culti-
vation is still necessary. The earlier this is done
in the winter, the more adverse effect it will have
on overwintering borer populations. Tilling as
late as February on the High Plains will greatly
reduce overwintering populations. To obtain max-
imum benefits, however, tilling should be done on
an areawide basis to reduce the total population in
an area and to counteract infestations resulting
from moth migration. Corn planted early is less
susceptible to plant lodging caused by the corn
borer, and often escapes heavy borer populations.
A reasonable plant population (22,000 to 24,000/
acre) to ensure large,. healthy stalks, along with
proper fertilization and adequate irrigation, will
help prevent lodging of borer-infested stalks.
Crop rotation, the use of early-maturing varie-
ties, and early harvest with equipment designed
to pick up lodged stalks are the most effective
practices in avoiding yield losses from the borer.
In fields which suffer fairly heavy infestations,
lodging and yield loss can be avoided by early
harvest. Most lodging occurs when harvest is de-
layed until late in the fall and infested plants are
subjected to wind and rain that eventually cause
the stalks to break.
Several beneficial insects, including predators
and parasites, play an important part in control-
ling southwestern corn borer populations. Some of
the more common predators include both the lar-
val and adult stages of the lady beetle, the larvae
of the green and brown lacewing, the flower bug,
several members of the assassin bug group and a
large number of spiders. Little information is
available on the various important parasites, al-
though one of the Trichogramma wasps does attack
corn borer eggs. Dipterous "scavenger" larvae fre-
quently have been found in conjunction with over-
wintering corn borer larvae.
Much data have been collected in Texas during
the past several years on chemical control of the
southwestern corn borer. Tests conducted in the
Texas Panhandle generally have given sporadic re-
sults, and treatments applied before mid-July 01"
after mid-August have generally proved ineffective.
Timing of insecticide applications is extremely crit-
ical, since little control will be obtained after the
borers have entered the plant. Chemical applica-
tion generally is not needed until egg masses and
larvae of first generation moths appear in mid-
July and early August. The need for treatment
should be based on the presence and abundance of
egg masses or young larvae, as determined during
field inspections.
Insecticides should not be applied even in July
on the High Plains until at least 35 percent of the
stalks are infested wi th egg masses or young larvae.
On late-planted corn, treatment should be initiated
at a lower infestation level. If the decision is made
to treat, a maximum of two applications applied
at a 10- to l4-day interval should give the most
economic control. Base the need for a second treat-
ment on plant infestation levels. If borers have
already entered the stalk, it is doubtful that any
economic gain will be obtained by treatment.
Plea e refer to Table 1 for chemicals which are
regi tered for corn borer con trol.
Level of infestations can be determined by care-
fully checking each field. A minimum of ten plants
should be examined at each location, and at least
five locations hould be checked in each field of
50 acres or les. On larger fields, additional checks
are ugge ted. Carefully observe the leaves, top and
bottom, at about ear height. Some of the plants
should be checked thoroughly. Refer to the section
on "Description" for information on identifying
egg rna ses and young larvae.
Spider Mite Complex
Several species of mites readily attack corn. The
Banks grass mite is the predominate species, and
was first reported in the Texas Panhandle in 1954
on wheat and grain sorghum. Serious damage to
corn was first observed in 1967. Since that time
frequent outbreaks have occurred on both grain
sorghum and corn. Although mites are observed
earlier in the growing season, population increases
generally occur after the tassel stage of plant
growth. Initial infestations appear on the lower
leaves. If the infestation is heavy the lower leaves
may be killed and the mites will move up the
plant.
Description and Life Cycle
Eggs of the Banks grass mi te are laid on the
leaf in webbing which the mites produce. The
egg are spherical and about ~ the size of the
adult, or about half the size of a period in ordinary
new print. They are transparent to pearly white
when first laid, but gradually change to a straw
yellow. The eggs hatch in 3 to 4 days under opti-
mum conditions, but several weeks may be required
when cool, moist conditions exist.
The small, ix-legged larvae are light colored
when first hatched but become dark green as they
feed. After everal days they molt (shed outer skin)
to the eight-legged nymphal stage and feeding con-
tinues. After two additional molts, the mites
emerge as adults. The males are smaller than the
females. Mating occurs soon after the females
emerge. Both males and females mate more than
once. The females lay an average of one egg per
day for approximately 48 days, although egg laying
may last as long as 80 days.
Minimum developmental time from egg to
adult is 8 to 10 days with favorable (hot, dry) con-
ditions. In addition to corn and sorghum, these
mites are found on small grains and numerous
grasses. Wheat is the main overwintering host in
the Texas Panhandle.
Control
umerous beneficial insects feed on both mites
and mite eggs, and while they do not always hold
mite populations in check, under favorable condi-
tions they can greatly reduce the populations. The
most common predators include predacious thrip ,
predacious mites, lady beetles (larvae and adults),
lacewing larvae and Orius or flower bugs. Weather
is the most effective control. Hard, driving rain
or a period of cool, wet weather will greatly reduce
mi te populations.
The use of pesticides for corn borer control may
significantly reduce beneficial insect populations
and "release" damaging mite populations. Some
pesticides appear to stimulate mite reproduction
and cause population increases. If damaging mite
populations do occur chemical control may be nec-
essary. Precise economic thresholds for mite dam-
age have not been established. When mites and
webbing are easily found in the middle third of the
plant, with visible damage (silver mottling) on the
leaves, controls should be initiated. However,
after corn reaches the hard dough stage there i
little economic advantage to be gained from using
pesticides. And in some areas mites have become
resistant to pesticides. For more information on
chemical control, refer to MP-339, Suggestions for
Controlling Insects and Mites on Corn J Sorghum
and Small Grains (Texas Agricultural Extension
Service), or refer to the insecticide summary in
Table 1.
Other Pests
Certain other insects do attack corn in Texas.
The corn earworm and the fall armyworm are
responsible for both leaf ragging and grain damage.
The corn earworm is well known to corn grow-
ers when found in the ear. However, when found
on other parts of the plant it may be mistaken for
another insect larva because of color variations.
Corn earworm moths deposi t eggs on the leaves,
tassels or silks, and the newly hatched larvae begin
to feed almost immediately. 't\Thorl feeding often
occurs, but larvae seldom reach the growing tip of
the plant. Chemical control of this pest is difficult
and not recommended. Numerous predators and
parasites commonly attack the corn earworm.
The fall armyworm is often mistaken for the
corn earworm. Grain and forage yields generally
have not been increased by the use of insecticides
against this pest. Early plantings of corn have
fewer corn earworms and fall armyworms than late
plantings.
There are three species of rootworms that dam-
age corn in the United States, and all three species
are known to occur in Texas. Economic damage
has been limited to the northern Panhandle, and
has been primarily caused by the western corn
rootworm. At the present time only isolated areas
have had rootworm problems, but with the con-
tinual increase in corn acreage severe problems may
eventually develop. Crop rotation will help reduce
this problem if it develops.
stands during certain years. White grubs are a
problem in some areas. The corn leaf aphid is
present every year but no economic losses have been
known to occur in Texas.
Grasshoppen occasionally cause leaf damage.
The seed-corn beetle} as well as wireworms of vari-
ous pecies, often damage newly planted seed.
umerou armyworms and cutworms may thin
FIELD CORN
Insecticides
(listed alphabetically)
Days from
last
application to Remarks
Pest
Toxicants per
gallon or pound
Concentrate
per acre
Har-
vest
Graz-
ing
Topical application. Broadcast by air or
direct granules or spray into whorl and/
or leaf sheath area with ground equip-
ment. Apply when second generation
eggs begin to hatch. See page 2 to
determine need for and timing of applica-
tions.
Carbaryl - Application to the tassel
area of the plants during the pollen shed
period will seriously reduce bee popula-
tions.
Carbofuran - Do not make foliage ap-
plication if more than 1.0 lb. actual
carbofuran was applied at planting. Do
not make more than two foliage applica-
tions per season.
Diazinon - Temporary spotting of foliage
may occur following application.
Size and maturity of plants will dictate
the need for application. Rese,arch has
shown no yield increase or reduced
lodging following treatments in the hard
dough or later stages of plant growth.
Erratic control with all recommended ma-
terials has been experienced in some
areas of Texas. Thorough plant' cover-
age is required.
Carbophenothion and phorate - Apply
only once per season.
o
o
10
o
o
o10 Ibs.
1 '/2 qts.
7-14 Ibs.
B. Carbofuran
(Furadan® lOG)
A. Carbaryl
(Sevimol-4®)
A. Carbophenothion pt. 21 21
(Trithion® 4 Ibs.) See remarks
B. Diazinon® (4 Ibs.) pt. 0 0
C. Disulfoton
(Di-Syston®)
(6 Ibs.) 2/3 pt. 28 28
(15%G) 3 1/ 2 -4 Ibs. 40 40
D. Ethion® (4 Ibs.) pt. 50 See
remarks
E. Parathion (4 Ibs.) 1/2 -1 pt. 12 12
F. Phorate 5-6 Ibs. 30 30
(Thimet® 15%G)
G. Sulfur 30-35 Ibs. 0 0
(50% dust)
C. Diazinon®
(14.3%G)
Disulfoton - Do not apply more than
twice per season regardless of method
of application. Use granular formulation
as whorl application only. Rates based
on 40-inch rows.
Ethion - Do not apply more than once
after ears form. Do not feed treated for-
age to livestock. Has been effective only
in South Texas and Gulf Coast areas.
Parathion - Two or more applications
may be required.
Phorate - One application per season.
Do not apply under prolonged drought
cond itions.
Sulfur - This is the only material which
has been partially effective in the Trans-
Pecos area of Texas. Thorough plant
coverage is required.
The original manuscript for this publication was prepared by B. C. Clymer, former area Extension
entomologist, Amarillo; and Norris Daniels, associate professor, Texas Agricultural Experiment Station,
Bushland, The Texas A&M University System.
The information given herein is for educational purposes only. Reference to commercial products or trade names is made
with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Se1lJice is implied.
Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socio-economic
levels, race, color, sex, religion or national origin.
Southwestern
corn borer
Spider mite
complex
Cooperative Extension Work in Agriculture and Home Economics, The Texas A&M University System and the United States
Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, 1914, as amended, and
June 30, 1914.
10M-2-76, New AGR 1


Insect and Mite Pests of Field Corn.

OAKTrust Digital Repository (Texas A&M Univ)

L-1417INSECT AND MITE PESTS OF FIELD CORNG. Mike McWhorterExtension EntomologistThe Texas A&M University SystemLife CycleThe southwestern corn borer overwinters as afull-grown larvae and usually hibernates at or nearthe base of the plant crown. The hibernation siteis in a "tunneled out" area wi thin the plant. Theupper part of the tunnel is clo ed with a toughsilken plug for protection. In the spring the borerextends its tunnel to the outer wall of the crown,leaving a thin covering which the moth can easilypush aside. Pupation then follow, and the mothsoon emerges from the tub of the stalk. Matingoccurs within a couple of days and eggs are gluedto the plant, usually on the top side of a leaf abouthalf way up the stalk. The eggs hatch within afew days, depending on the temperature.generally average four or five per group. The colorand appearance of the eggs change as the incuba-tion period progresses. Three parallel rows of red-dish-orange lines appear prior to hatching, and thecolor changes to yellow, orange-yellow or reddish-brown before hatching.After the egg hatch, the small larvae closelyresemble the full grown "worm," which is from Ito I Y4 inches long and dull white or yellowi h-white in color. The larvae also have a regular pat-tern of dark brown polka dot which generally di -appears in the creamy yellow overwintering form.The mahogany brown pupae are slightly shorterthan the larvae. They are normally found withinthe corn stalk during the summer, and in the crownof the plant just below the oil surface in thespnng.The moths are from 3/5 to 3/4 inch long witha wing spread of I Y4 inches. They are solid whiteto pale yellow and fold the wings about the bodywhen at rest. A characteristic snout extends fromthe head.Corn acreage in Texa is increasing. Irrigatedcorn acreage increa ed from 602,000 acres in 1966to more than 1,100,000 acres in 1975. Therefore,corn in ect pest control is becoming increasinglyimportant.V\ ith the expansion of an agricultural crop,insect and mite pests and their damage generallyalso increa e. Al though use of pesticides cannotbe eliminated, every effort must be made to usethem in an economical and scientifically soundmanner. Along with u ing the lowest possible effec-tive dosage of pe ticide, and using them onlywhen needed, other important control proceduresinclude variou cultural practices, biological con-trol method and planting resistant varieties. Thedevelopment of re i tant or tolerant varieties mayhold the greate t promi e for corn insect controlin the future. In any case, an effective pest controlprogram is an integrated program based on cul-tural and mechanical practices as well as the useof pe ticide .umerous arthropods (insects and mites), bothharmful and beneficial, are commonly found incorn. But only the southwestern corn borer andcertain spider mites (primarily the Banks grass mite)are of major concern at this time.Southwestern Corn BorerThe southwestern corn borer was first found inthe United States in 1913. It spread north and eastfrom Mexico into the Texas Panhandle, and wase tablished in Colorado, Kansas and Oklahoma by1931. It has become the major pest in irrigatedcorn growing regions of Texas, especially in theHigh Plains.DescriptionThe egg are elliptical to oval, flattened, slightlyconvex on the upper surface, and translucent whitewhen fir t laid. They are quite small and average1.2 to 1.6 mm in length by 0.8 to I mm in width.The borer lay its eggs in chains or groups thatoverlap much like fi h scales or roof shingles. Eggsmay be found in groups of two to 50 or more, but19.12StageEggLarvaPupaAdultDevelopmental PeriodsAverage no. of days525105Texas Agricultural Extension Service • The Texas A&M University System • H. O. Kunkel, Acting Director • College StationSEASONAL HISTORYCORN BORER ONOF THE SOUTHWESTERNTEXAS HIGH PLAINSINDICATES TIME FIELDSSHOULD BE SCOUTED TODETERMINE NEED TO CONTROLSOUTHWESTERN CORN BORER.APRIL15MAY15DIAPAUSINGJUNE15JULY15AUGUST·,'1' ." .: .. ·· .. :,:'15:::::;:"":.SEPTEMBER15OCT-MARCHControlCultural practices play a critical role in man-aging the southwestern corn borer. Fall or winterstalk destruction through double disking, chiselingand deep breaking destroys the plant crown andincreases overwintering larval mortality.When stalks are grazed out, some type of culti-vation is still necessary. The earlier this is donein the winter, the more adverse effect it will haveon overwintering borer populations. Tilling aslate as February on the High Plains will greatlyreduce overwintering populations. To obtain max-imum benefits, however, tilling should be done onan areawide basis to reduce the total population inan area and to counteract infestations resultingfrom moth migration. Corn planted early is lesssusceptible to plant lodging caused by the cornborer, and often escapes heavy borer populations.A reasonable plant population (22,000 to 24,000/acre) to ensure large,. healthy stalks, along withproper fertilization and adequate irrigation, willhelp prevent lodging of borer-infested stalks.Crop rotation, the use of early-maturing varie-ties, and early harvest with equipment designedto pick up lodged stalks are the most effectivepractices in avoiding yield losses from the borer.In fields which suffer fairly heavy infestations,lodging and yield loss can be avoided by earlyharvest. Most lodging occurs when harvest is de-layed until late in the fall and infested plants aresubjected to wind and rain that eventually causethe stalks to break.Several beneficial insects, including predatorsand parasites, play an important part in control-ling southwestern corn borer populations. Some ofthe more common predators include both the lar-val and adult stages of the lady beetle, the larvaeof the green and brown lacewing, the flower bug,several members of the assassin bug group and alarge number of spiders. Little information isavailable on the various important parasites, al-though one of the Trichogramma wasps does attackcorn borer eggs. Dipterous "scavenger" larvae fre-quently have been found in conjunction with over-wintering corn borer larvae.Much data have been collected in Texas duringthe past several years on chemical control of thesouthwestern corn borer. Tests conducted in theTexas Panhandle generally have given sporadic re-sults, and treatments applied before mid-July 01"after mid-August have generally proved ineffective.Timing of insecticide applications is extremely crit-ical, since little control will be obtained after theborers have entered the plant. Chemical applica-tion generally is not needed until egg masses andlarvae of first generation moths appear in mid-July and early August. The need for treatmentshould be based on the presence and abundance ofegg masses or young larvae, as determined duringfield inspections.Insecticides should not be applied even in Julyon the High Plains until at least 35 percent of thestalks are infested wi th egg masses or young larvae.On late-planted corn, treatment should be initiatedat a lower infestation level. If the decision is madeto treat, a maximum of two applications appliedat a 10- to l4-day interval should give the mosteconomic control. Base the need for a second treat-ment on plant infestation levels. If borers havealready entered the stalk, it is doubtful that anyeconomic gain will be obtained by treatment.Plea e refer to Table 1 for chemicals which areregi tered for corn borer con trol.Level of infestations can be determined by care-fully checking each field. A minimum of ten plantsshould be examined at each location, and at leastfive locations hould be checked in each field of50 acres or les. On larger fields, additional checksare ugge ted. Carefully observe the leaves, top andbottom, at about ear height. Some of the plantsshould be checked thoroughly. Refer to the sectionon "Description" for information on identifyingegg rna ses and young larvae.Spider Mite ComplexSeveral species of mites readily attack corn. TheBanks grass mite is the predominate species, andwas first reported in the Texas Panhandle in 1954on wheat and grain sorghum. Serious damage tocorn was first observed in 1967. Since that timefrequent outbreaks have occurred on both grainsorghum and corn. Although mites are observedearlier in the growing season, population increasesgenerally occur after the tassel stage of plantgrowth. Initial infestations appear on the lowerleaves. If the infestation is heavy the lower leavesmay be killed and the mites will move up theplant.Description and Life CycleEggs of the Banks grass mi te are laid on theleaf in webbing which the mites produce. Theegg are spherical and about ~ the size of theadult, or about half the size of a period in ordinarynew print. They are transparent to pearly whitewhen first laid, but gradually change to a strawyellow. The eggs hatch in 3 to 4 days under opti-mum conditions, but several weeks may be requiredwhen cool, moist conditions exist.The small, ix-legged larvae are light coloredwhen first hatched but become dark green as theyfeed. After everal days they molt (shed outer skin)to the eight-legged nymphal stage and feeding con-tinues. After two additional molts, the mitesemerge as adults. The males are smaller than thefemales. Mating occurs soon after the femalesemerge. Both males and females mate more thanonce. The females lay an average of one egg perday for approximately 48 days, although egg layingmay last as long as 80 days.Minimum developmental time from egg toadult is 8 to 10 days with favorable (hot, dry) con-ditions. In addition to corn and sorghum, thesemites are found on small grains and numerousgrasses. Wheat is the main overwintering host inthe Texas Panhandle.Controlumerous beneficial insects feed on both mitesand mite eggs, and while they do not always holdmite populations in check, under favorable condi-tions they can greatly reduce the populations. Themost common predators include predacious thrip ,predacious mites, lady beetles (larvae and adults),lacewing larvae and Orius or flower bugs. Weatheris the most effective control. Hard, driving rainor a period of cool, wet weather will greatly reducemi te populations.The use of pesticides for corn borer control maysignificantly reduce beneficial insect populationsand "release" damaging mite populations. Somepesticides appear to stimulate mite reproductionand cause population increases. If damaging mitepopulations do occur chemical control may be nec-essary. Precise economic thresholds for mite dam-age have not been established. When mites andwebbing are easily found in the middle third of theplant, with visible damage (silver mottling) on theleaves, controls should be initiated. However,after corn reaches the hard dough stage there ilittle economic advantage to be gained from usingpesticides. And in some areas mites have becomeresistant to pesticides. For more information onchemical control, refer to MP-339, Suggestions forControlling Insects and Mites on Corn J Sorghumand Small Grains (Texas Agricultural ExtensionService), or refer to the insecticide summary inTable 1.Other PestsCertain other insects do attack corn in Texas.The corn earworm and the fall armyworm areresponsible for both leaf ragging and grain damage.The corn earworm is well known to corn grow-ers when found in the ear. However, when foundon other parts of the plant it may be mistaken foranother insect larva because of color variations.Corn earworm moths deposi t eggs on the leaves,tassels or silks, and the newly hatched larvae beginto feed almost immediately. 't\Thorl feeding oftenoccurs, but larvae seldom reach the growing tip ofthe plant. Chemical control of this pest is difficultand not recommended. Numerous predators andparasites commonly attack the corn earworm.The fall armyworm is often mistaken for thecorn earworm. Grain and forage yields generallyhave not been increased by the use of insecticidesagainst this pest. Early plantings of corn havefewer corn earworms and fall armyworms than lateplantings.There are three species of rootworms that dam-age corn in the United States, and all three speciesare known to occur in Texas. Economic damagehas been limited to the northern Panhandle, andhas been primarily caused by the western cornrootworm. At the present time only isolated areashave had rootworm problems, but with the con-tinual increase in corn acreage severe problems mayeventually develop. Crop rotation will help reducethis problem if it develops.stands during certain years. White grubs are aproblem in some areas. The corn leaf aphid ispresent every year but no economic losses have beenknown to occur in Texas.Grasshoppen occasionally cause leaf damage.The seed-corn beetle} as well as wireworms of vari-ous pecies, often damage newly planted seed.umerou armyworms and cutworms may thinFIELD CORNInsecticides(listed alphabetically)Days fromlastapplication to RemarksPestToxicants pergallon or poundConcentrateper acreHar-vestGraz-ingTopical application. Broadcast by air ordirect granules or spray into whorl and/or leaf sheath area with ground equip-ment. Apply when second generationeggs begin to hatch. See page 2 todetermine need for and timing of applica-tions.Carbaryl - Application to the tasselarea of the plants during the pollen shedperiod will seriously reduce bee popula-tions.Carbofuran - Do not make foliage ap-plication if more than 1.0 lb. actualcarbofuran was applied at planting. Donot make more than two foliage applica-tions per season.Diazinon - Temporary spotting of foliagemay occur following application.Size and maturity of plants will dictatethe need for application. Rese,arch hasshown no yield increase or reducedlodging following treatments in the harddough or later stages of plant growth.Erratic control with all recommended ma-terials has been experienced in someareas of Texas. Thorough plant' cover-age is required.Carbophenothion and phorate - Applyonly once per season.oo10ooo10 Ibs.1 '/2 qts.7-14 Ibs.B. Carbofuran(Furadan® lOG)A. Carbaryl(Sevimol-4®)A. Carbophenothion pt. 21 21(Trithion® 4 Ibs.) See remarksB. Diazinon® (4 Ibs.) pt. 0 0C. Disulfoton(Di-Syston®)(6 Ibs.) 2/3 pt. 28 28(15%G) 3 1/ 2 -4 Ibs. 40 40D. Ethion® (4 Ibs.) pt. 50 SeeremarksE. Parathion (4 Ibs.) 1/2 -1 pt. 12 12F. Phorate 5-6 Ibs. 30 30(Thimet® 15%G)G. Sulfur 30-35 Ibs. 0 0(50% dust)C. Diazinon®(14.3%G)Disulfoton - Do not apply more thantwice per season regardless of methodof application. Use granular formulationas whorl application only. Rates basedon 40-inch rows.Ethion - Do not apply more than onceafter ears form. Do not feed treated for-age to livestock. Has been effective onlyin South Texas and Gulf Coast areas.Parathion - Two or more applicationsmay be required.Phorate - One application per season.Do not apply under prolonged droughtcond itions.Sulfur - This is the only material whichhas been partially effective in the Trans-Pecos area of Texas. Thorough plantcoverage is required.The original manuscript for this publication was prepared by B. C. Clymer, former area Extensionentomologist, Amarillo; and Norris Daniels, associate professor, Texas Agricultural Experiment Station,Bushland, The Texas A&M University System.The information given herein is for educational purposes only. Reference to commercial products or trade names is madewith the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Se1lJice is implied.Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socio-economiclevels, race, color, sex, religion or national origin.Southwesterncorn borerSpider mitecomplexCooperative Extension Work in Agriculture and Home Economics, The Texas A&M University System and the United StatesDepartment of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, 1914, as amended, andJune 30, 1914.10M-2-76, New AGR 1

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Insect and Mite Pests of Field Corn.

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