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Mississippi Agricultural and Forestry Bulletins Experiment Station (MAFES)

5-1-1969

The Southwestern corn borer and its control

C. A. Henderson

Frank M. Davis

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Recommended Citation Henderson, C. A. and Davis, Frank M., "The Southwestern corn borer and its control" (1969). Bulletins. 140. https://scholarsjunction.msstate.edu/mafes-bulletins/140

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BULLETIN 773 MAY 1969

The Southwestern Corn Borer

And fts Control

By C. A. HENDERSON and FRANK M DAVIS

Figure 1. Known distribution of the southwestern corn borer in the United States.

Mississippi State University AGRICULTURAL EXPERIMENT STATION JAMES MMvritci. MfcMORlAL j UBRARY STATE COLLEGE t MISSISSIPPI In Cooperation With The Entomology Research Division Agr. Res. Ser. U.S.D.A:

MISSISSIPPI STATE UNIVERSITY . )

TABLE OF CONTENTS

Page Page List of common and scientific Natural enemies 13 names of discussed 2 Larvae mistaken for the south- Description and habits 3 western corn borer 14 Damage __ 7 Corn earworm 14 Control -- 10 Fall armyworm 15 Adjusting planting dates 10 Southearn cornstalk borer 15

Chemical control on corn . 10 European corn borer 16 Equipment for applying insecticide/; 12 borer 16 Cultural practices for control 13 Summary 16

COMMON AND SCIENTIFIC NAMES OF INSECTS DISCUSSED

Common Name Scientific Name

A mite Caloglyphus sji. C>()rn earworm Heliothis (Hoddie) European corn borer Ostrinia nubilalis (Hbn.) Fall armyworm Spodoptera frugiperda (Smith) Southern cornstalk borer crambidoides ((^rote) Southwestern corn borer Diatraea grandiosella (Dyar) Sugarcane borer Diatraea saccharalis (F.

None Trichogramma minutum (Rile\ )

I

J- »

. it/-

Figure 2. Overwintering in the base of a cornstalk. THE SOUTHWESTERN CORN BORER AND ITS CONTROL

By C. A. HENDERSON and FRANK M. DAVIS

in.sect varies The southwestern corn borer is one with latitude but may be of the most dGstructive pests of corn also influenced by weather. In its nor- in the South and Southwest. Since first thern-most areas there are only two reported in the United States from generations per year. In southern areas three generations and partial Lakewood New Mexico in 1913 it has a fourth may spread eastward to Central Alabama and develop annually. Central Tennessee and northward to sou- Full-grown creamy-white larvae over- thern Kansas. All or portions of 14 states winter in the lowest part of the main stem of the host plant (Fig. are in tested (Fig". 1 ). 2). These larvae pupate in the base of the old All types of corn are the preferred stalks from April 15 to May 15 and hosts; however, .s, sugarcane, first generation adults (Fig. emerge broomcorn, Sudangrass and Johnsongrass 3) from May 1 to May 30. Figure 3A shows are hosts. the approximate length of generations Description and Habits and the time each occurs during the year. This may vary a week from year The southwestern corn borer has four t(j year. stages in its lile cycle: egg, larva or borer, , and adult. The eggs are commonly oviposited The number of generations of this sintilv m a cham or m a mass and

Figure 3. ; male on left, female on right. 4 MISSISSIPPI a(;ri(:ultural experiment station bulletin 773

D

B Bi

I I 1 1 1 I I_ SEPT. APRIL MAY JUNE JULY AUG. SEPT.

A-Overwintering Generation D-Third Generation B - First Generation Ai ,B,,C, - Flights C- Second Generation "-- Small Part Of Second And All Of Third Generation Overwinter

Figure 3-A. Length of generations and time each occurs.

Figure 4. Fresh oviposited egg mass. Figure 5. Egg mass with transverse orange-red bands. SOUTHWESTERN CORN ER AND ITS CONTROL 5

level during the summer, is milky-white with a brown head, and brownish- black dots on the body. The winter form (Fig. 7) occurs in the base of the. nlanr usually below ground level from October

to April, This form is a light creamy- yellow color or a little darker than the summer form, and the head less intense-

ly brown. The brownish - black dots of the summer form are missing in the winter form. When full grown the larva

is about 1 inch long. Many overwintering larvae girdle the stalk internally near or a few inches above ground level from

mid-August to mid - October causing

Figur* 6. Summer form of full*grown larva of southwestern corn borer.

overlap one another as shingles on a root (Fig. 4). The average number of eggs per mass is 2. They are very small and are usually found on the upper arkJ lower surface of the corn leaf, but some have been found on the stalk. When first oviposited the eggs are green- ish white. They gradually become lighter tor 24 to 36 hours gradually becoming cream colored with 3 parallel transverse orange-red lines dividing each egg into 4 more or less equal parts (Fig. 5). About 24 hours before hatching the egg becomes a light yellowish color and the head of the enclosed larva may be seen through the shell as a black spot.

The incubation period is from 4 to 7 days.

The larvae of the southwestern corn borer present a summer and a winter form. The summer form (Fig. 6) Figure 7. Winter form of full-grown lar- occurs in the corn plant above ground va of southwestern corn borer.

SOUTHWESTERN CORN BORER AND ITS CONTROL 7

Figure 10. A girdled cornstalk. the plants to fall over. .Not all of the Bud injury to young corn by the larvae larvae girdle the stalks. is often serious. This destruction of the leaves of the young plant is On completing its development the larva central heart," and transforms into the pupa or resting commonly called "dead die or to become stage (Fig. 8). The newly formed pupa causes the plant to stunted, and unproductive is ahout the same color as the larva. deformed, to the plant can be It gradually a.ssumes a dark-hrown color. (Fig. ^). Injury

several ways: ( I young plants The pupa ranges hetwcn one-half and caused in ) borer activity one inch in length. The average weight are killed or dwarfed by in the stalk; yield is reduced by ot the pupae is females 257 mg, males (2) 124 mg. extensive tunneling in the stalks; and (3) grain is l(jst as a result of stalk T he adult is a dull white colored moth. girdling ( I'ig. 10) in the fall. Females have a wing span of ^0 to 40 mm and males have a wing span of Stalk girdling is the result of over- 20 to ^0 mm. When at rest the wings wintering larvae cutting a V - shaped are loldetl close over the hody. The grtxne around the inside of the stalk males arc slightly smaller than the near, or a few inches abcne, ground lemales and a little darker in color level, (iirdling activity (jccurs generally (hig. 5). h'cmales oviposit an average from mid-August until harvest. Some ol about ^SO eggs. 'I'he average longevity infested stalk.s escape girdling entirely, lor all generations was 4.4 days for and others are n(jt girdled sufficiently temales and 4.1 days for males. to cause breakage, but many girdled

stalks I all of their (nvn weight or are Damage blown (j\er by wind (hig. 1 1 ). The loss

Injury to the plant is causec] exclusively caused by , rot, and mcjld oc- bv the larva. Practically all parts of the casioned by this activity may be great, corn [)lant are damaged t(j some tlegrec, depending (jn weather conditions, pre- although the most severe in- valence ol rodents, and other factors.. jury results trom feeding on the growing Where mechanical harvesters arc used point or "hud," and the stalk profKrr. the lodged corn is picked. Salvage 8 MISSISSIPPI AGRICULTURAL EXPERIMENT STATION BULLETIN 773

Figure 11. Corn ttalks broken and lodged due to girdling by the larvae. SOUTHWESTERN CORN BORER AND ITS CONTROL 9

YIELD(1962) YIELD(1963)

120-

80-

40-

3/22 ^/lO ^/l ^^20 ^^22 "^^10 ^^1 ^^20 ^^10 Planting Dates

INFESTATION NFESTATION

60-

40-

20-

I ^ i i i

^^22 "^/lO ^/l ^^20 ^/22 "^/lO 5/l ^/20 ^^10

Planting Dates Girdling Girdling

"0 _a> -D 20- k. O

(/> c 10- _g o. d Z

5/ "^^10 3/22 "^/lO 5/l 20 3/22 5/l 5/20 ^^10 Planting Dates

Fig. 12. Yield, borer infestation and stalk girdling by planting dates in 1962-63. These data taken from a published report in Journ. Econ. Entomol. Vol. 60, No. 3, pp. 709-711, June 1967. STATION BULLETIN 773 10 MISSISSIPPI ACJRICULTURAL EXPERIMENT

cold, wet weather and early enough so the corn escapes some of the hot, dry weather that usually occurs late in the growing sea.son. In tests at State College and Stoneville, Miss, over a 2-year period, corn planted

by May 1 yielded significantly more and had significantly fewer plants infested and girdled than corn planted on May 20

and )une 10 (See Fig. 12). Therefore it is advisable to plant corn as early as practicable.

Early planting ot corn is the most prac- tical and economical method of control- ling the southwestern corn borer in Mis- sissippi. Chemical Control on Corn; C'hemical treatment may be desirable on highly

productive land or where the crop is of special value, such as corn groun fur seed production. Treatment of early-

planted corn generally is ot little or no

value. When it is necessary to plant corn

late, after May 10, it is usually beneficial to chemically control the borer, especi- ally in the north halt ot Mississip[)i. The timing ot applications ot chemicals

is critical tor control ot the southwestern corn borer. A black light trap (Fig, 13) located near the test field was used tor this purpose alter l^>64. One week alter the tirst .southwestern corn Figure 13. Black light insect trap. borer moth, ot a generation, was trapjxrd the first application ot insecticide was necessitates gleaning, an cx^xfnsive o[>era- made tor control ot that generation ol tion, unles.s lields are equipped so livestock borers. This usually cKcurs the last da\s can utilize the downed corn. ot june tor secontl generation borers, and the last tlavs ol |ulv or the tirst [>art ol Control August tor third generation borers at State College, Mississippi. 1' .u h m ner.i- C'ontrol of the southwestern corn borer l\ou ol borers occurs about 7 or M ila\s may be achievetl to some dci^ree by: later in the \ icimtv ol 1 loll\ Sjirings. Mis- early planting, cultural practices antl use sissif>[^i. and timing of insecticides.

Research is being conducted to develop Research to de\elop cluinical control hybrids that are tolerant or resistant to methods tor the southwestern corn borer this insect. in .\lississip[)i w as started in I "^^M , Ke- Adjusting planting dates: In Mississip- sults With the \arious insecticides were pi, maximum corn yiekls are obtained by obtained in experimental [)lots and shouKl selecting planting dales late enough so not be considered recommendations. In

seedling vigor will not be retluced by the first test 0.5 los. endrin, 1.5 lbs. car- AAAA A

SOUTHWESTERN CORN BORER AND ITS CONTROL H

were made at weekly intervals after the baryl and 2.0 lb/acre DDT in 30 gallons first. of water were applied into the whorls of Endrin was significantly more eftective the plants. Three applications at 1 week than carbaryl or diazinon in reducing the intervals were made beginning when the degree of infestation and the number of first larvae were observed on the plants. girdled stalks (Table 1). All treatments In 1962, 1963 and 1964 tests were con- were significantly better than the un- ducted at State College, Holly Springs, treated check. and Stoneville, Mississippi using granu- lar formulations of endrin 0.5 lb., and Tn 1966 and 1967 a four-treatment ap- carbaryl 1.5 lb/acre. Diazinon granules plication schedule was followed. Two ap- 1.25 lb/acre were tested in 1964, and car- plications a week apart were made for bofuran granules at a rate of 1.0 lb/acre control of second generation borers and were included in the 1964 tests. The first two applications a week apart for con- of three applications of the chemicals trol of the third generation borers. The was made when approximately 25°{, of granular insecticides were applied into the plants showed leaf-feeding by th e the whorl of the corn plants for second young borers. The other two applications generation borer control, or to the ear

Table 1. Tests of control of the southwestern com borer with 3 applications of insecticides in 1964

Treatment % stalks % s*alks Yield infested girdled (Bu/A)

Holy Springs, Miss.

Endrin gran. 0.5 lb/ 24.2a 8.5a 45.7a Diazinon gran. 1.25 lb/ 63.8b 30.5b 44.8a Carbaryl gran. 1.5 lb/ 73.9c 36.8c 40.5a Check (untreated) 87.8d 45. Od 39.4a Stojieville, Miss.

Endrin gran. 0.5 lb/ 51.1a 16.4a 53.1a Diazinon gran. 1.25 lb/ 73.4b 24.0b 50.0a Carbaryl gran. 1.5 lb/ 82.2c 27.8bc 50.9a Check (untreated) 95.9d 31.4c 35.1b

These data are taken from published report in Journ. Econ. Entomal. Vol. 60, No. 3 pp 629 - 634, June 1967.

Table 2. Tests of control of the southwestern com borer with 4 applications of insecticides in 1967.

Treatment % stalks % stalks Yield infested girdled (Bu/A)

Holy Springs, Miss.

Carbofuran gran., 0.5 lb/ 13.0a 2.0a 77.1a Endrin gran., 0.5 lb/A 14.4a 5.0a 71.5a Endosulfan gran., 0.5 lb/ 19.0a 7.0a 68.7a Check (untreated) 71.0b 42.0b 59.4a State College, Miss.

Endrin gran. 0.5 lb/ 15.8a 5.5a 40.2a Carbofuran gran. 0.5 lb/A 13.5a 5.8a 39.0a Endosulfan gran. 0.5 lb/A 11.2a 6.8a 38.0a Check (untreated) 75.5b 29.8b 30.7a

All means followed by the same letter are not significantly different at the 5% level, as determined by Duncan's New Multiple Range Test. 12 MISSISSIPPI AGRICULTURAL EXPERIMENT STATION BULLETIN 773

'7

Figure 14. Hahn Hl-Boy machine used to apply insecticides.

plants tor third zone area ot the genera- some promise as a systemic in-secticide tion borer control. when 3 applications were made at plant- Endrin, endosulfan and carbofuran ing time, mid-June and mid-July.

each applied at a rate of 0.5 lb. active Equipment for Applying Insecticides: ingredient per acre per application gave A Hahn Hi-Boy machine was used to a{> significantly better borer control than ply the insecticides. However, most any the untreated check (Table 2). No sig- high-cleannice machine is or can be nificant differences borer in control were made adequate for insecticide applica- noted chemicals. among tions. Equipment for attaching to a high- clearance for the application of Azodrin emul.sifiable concentrate at a machine granular insecticides is available com- rate of 1.0 lb. in 16 gallons of water per acre per application using two applica- mercially. Kow-crop dusters are not sat- tions for control of second generation isfactory I'lr applying granules. borers applications for third and two A two row (landy hopper attached to generation borers gave significantly bet- a Hahn Hi hov machine was adjusted to ter borer control than the untreated distribut' tlie pro[xr amount of insecti- check in 1966 and 1967. cide in i.esrs at State College and Holly Springs, i^is (I'lg. 14). A small hydrau- Carbofuran granules (3°o) applied to lic adiacent to the hopper the soil at a rate of one pound actual ma- motor mounted (Fig. i4; was used to operate the hop- terial per acre, f)er application showed SOUTHWESTERN CORN BORER AND ITS CONTROL 13

Figure IS. peck hole in cornstalk.

pcr's agitator, thus insurioix a steady Figure 16. Corn earworm (Photo by

I low ot grannies. Southern Grain Insects Research Labor- atory, Tifton, Ga.) Cultural Practices for Control: The Overwmtering borers ctfeci (jt tall plowing and disking on borer are' susceptible t(j winter temperatures surxival was determined. Over a 3-year when not protect- ed by soil around period, each tall corn stalks were either the stubble. Fall disk- ing ot corn stubble double disked with a tandem di.sk or will kill some b(jrers and many die thrown out ot the row with a middle trom e.xpcjsure \o weather and natural enemies. buster plow in three ditlerent areas ot' a tield. The following April ot each year Natural Enemies

100 rantlomly selected stalks in each ot Trichogramma minutum (Kiley) is a the three areas were split and the south- parasite the southwestern c(jrn borer. western corn borer mortality was calcu This minute, yellow, hvmenoptercjus in- lattd. The results show that tall iliskiui:'^ sect, which scarcely can be seen with the

\\\\\ reduce ovcrwintcrm;4 populations (j1 unaided eye, (jvip(jsits in the eggs ot the the b(jrcr about V8 percent. hlowe\er, li borer. Parasitized borer eggs become

iliskmu is ot in black I ail to to be value reducing l^^M^' and hatch. The degree ot ulations ol the southwestern corn borer. has been light in Mississippi.

It iinist be [)raciiced o\er ;i large i>eo A mite, Caloglyphus sp., has been ob- gra[)hical area. The adult insects aie served clinging lo die (a erwintering lar- strong llicrs and caii migrate Xnnvi un- vae m iIk- base <;! the stem ot the corn-

- disked tiekls . Deep plowing has nul stalks m tile lall and winter. No more en satistaciorv control. than 3 mites |)er live larva have been ob- 14 MISSISSIPPI y\C;RICULTURAL EXPERIMENT STATION BULLETIN 773

served in the field. Several ot these lar- va were brou<^ht into the laboratory and 66.0% to 0% in M) examined fields, it ap- isolated until they died or pupated. Alter ^>eared to be greatest in fields adjacent the death of a larva the mites multiplied to or near the wcMnied areas. rapidly. Mites have also been found on southwestern corn borer pupae. These Larvae Mistaken for the Southwestern mites are scarce ni the held and ot Corn Borer doubtful importance. A bird, the flicker, (Colaptes auratus) Se\eral lar\ae tountl in corn, rithcr has lieen observed in the act of teedin^^ similar in appearance or type of dam;iue, on the overwintering larval sta^e ot the are otten mistaken lor the southwestern borer. This w^oodpecker has been seen corn borer. peckini^ holes in cornstalks (Fig. 15) us- Corn Earworm. The corn earworni ually from 1 to 3 inches above ground (Fig. 16) often feeds on the leaves in the level, and with his long, barbed tongue, whorl of the corn plant and causes dam- taking overwintering larvae from the age similar to that of the southwestern base of the stalk. Predation ranged from corn borer. Larval color ot the corn car- SOUTHWESTERN CORN BORER AND ITS CONTROL 15

Figure 19. European corn borer (Photo by Corn Borer Research Laboratory, An- keny, Iowa)

worm varies from tints of j^reen, pink, Figure 20. Sugarcane borer (Photo by yellow, and brown to almost black. When Sugarcane Borer Research Laboratory, fully grown, they are about l-'/^ inches Houma, La., and Abner Hammond, En- long, whereas the southwestern corn bor- tomologist, L. S. U.)

er is only about 1 inch in length. In ma- turing corn, the corn earworm feeds ex- tensively on the cars, whereas the south- They devour every leaf, leaving only the western corn borer occasionally damages toughest parts of the plant stems. the ear. Southern Cornstalk Borer: The larvae Fall Armyworm: Fall armyworm lar- of this insect Ujoks very much like the vae (Fig. 17) frecjuently feed on the larvae of the southwestern corn borer leaves and in the stalk and ear shank, (Fig. 18). They are about the same size and damage the ear bv feeding on the and their color combinations are very

grain. The young larvae .skeletcmize the similar. Damage to corn plants is almost leaves, leaving con.spicuous whitish pat- identical to that ot the .southwestern, ex- ches when seen against the green parts cept the southern cornstalk borer does ot the leaf. When fully grown the lar- not girdle the stalk. Also, the southern vae are stri[^>ed, nearly naked, and al- corn stalk borer larvae have a summer most 1-/2 inches in length. Their color form and a winter form, each closely re- ranges from light green to almost black. sembling those of the southwestern. 16 MISSISSIPPI AC.RICULTURAL EXPl IMENT STATION BULLETIN 773

European Corn Borer: Full-grown lar- long when full-grown. It is yellowish va overwinter inside a tunnel in the corn white with brown spots. In the winter stalk, stubble or ear of corn, or in weeds these spots are often absent and the

or other plant material. Almost 1 inch color becomes a deeper yellow. Injury

long with a dark brown or black head, to the plant is caused only by the larvae. and a gray to light brown or flesh-colored It tunnels inside the stalks, stunting body, the larva has rows of brown sp>ots the growth and sometimes killing young and several brown or pink lines extending plants. lengthwide (Fig. 19). The sugarcane borer overwinters as European corn borer damage is caused a larva within a tunnel it has made by the larvae feeding in and on various in its host plant. parts of the corn plant. Leaf feeding that Figure 21 shows 4 of the above lar- results in the destruction of the leaf sur- vae with the southwestern corn borer face, sheath girdling, and breakage of larva on a common background for com- the mid-ribs causes reduced yields. parison of size and color patterns. Stalk tunneling is similar to that of Summary the southwestern corn borer, except that The southwestern corn borer his been it seldom tunnels down into the bottom found in 14 states with Central Alabama of the stalk as is the case of the late and Central Tennessee the most eastern season southwestern larvae. At time of points known to be infested. tasseling European larvae tunneling in This pest attacks all types of corn, the tassel stems often causes the tas- -, sugarcane, broomcorn, Sud- sels to break over. angrass and [ohnsongrass. Injury to the Sugarcane Borer: Although this borer plant is caused exclusively by the lar- is primarily a pest of sugarcane, it va. readily attacks corn. The sugercane bor- Control of the southwestern corn bor- er is similar to the southwestern corn er mav be achieved to some degree borer and occurs along the gulf coast by earlv planting, cultural prartice^ from Florida to the Mexican border. anif l)v use and timing of insecticides.

E.Hi!^ jjlaniing is best. The larva (Fig, 20) is about 1 inch

Figure 21. Corn earworm, fall armyworm, European corn borer, sugarcane borer, and southwestern corn borer (left to right).