Mississippi State University Scholars Junction Mississippi Agricultural and Forestry Bulletins Experiment Station (MAFES) 5-1-1969 The Southwestern corn borer and its control C. A. Henderson Frank M. Davis Follow this and additional works at: https://scholarsjunction.msstate.edu/mafes-bulletins 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 This Text is brought to you for free and open access by the Mississippi Agricultural and Forestry Experiment Station (MAFES) at Scholars Junction. It has been accepted for inclusion in Bulletins by an authorized administrator of Scholars Junction. For more information, please contact [email protected]. -) ^ 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 insects 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 Sugarcane 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 zea (Hoddie) European corn borer Ostrinia nubilalis (Hbn.) Fall armyworm Spodoptera frugiperda (Smith) Southern cornstalk borer Diatraea crambidoides ((^rote) Southwestern corn borer Diatraea grandiosella (Dyar) Sugarcane borer Diatraea saccharalis (F. None Trichogramma minutum (Rile\ ) I J- » . it/- Figure 2. Overwintering larva 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, sorghum.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, pupa, and adult. The eggs are commonly oviposited The number of generations of this sintilv m a cham or m a mass and Figure 3. Moths; 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, -Moth 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 bears 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 rodents, 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.