THE SOUTHWESTERN CORN BORER IN ARKANSAS By L. H. Rolston AGRICULTURAL EXPERIMENT STATION College of Agriculture and Home Economics University of Arkansas, Fayetteville June, 1955 Bulletin 553 CONTENTS Page In tro d u c tio n ________________________________________________________________ 3 Review of Literature____ __________________________________________________ 3 L ife and Seasonal H is to ry _____________________________________________ —... 6 Description of Injury_________________________ ____________________________ ... 10 A d ut l _______________:________________________ _________________________________ 12 Egg------- 20 L a rva _______________________________________________________________________ 21 P re pu p a _____________________________________________________________________ 31 P upa________________________________________________________________________ 31 H osts Other Than Corn____________ ____________________ , __________________ 32 N a tural Enemies___________________________________________________________ 35 C o nrol t Methods____ .'.______________________________________________________ 36 S u m ma ry ____________________________________________________________________ 39 L ite ra tu re C ite d --------------------------------------------------------------------------------------------- 40 COVER PICTURE The two plants in the foreground are affected by “dead heart”. Notice the dead, blanched central leaves, excessive tillering, and stunting. The plant in the right background is of normal height. This bulletin covers the m aterial used in a thesis presented as partial fulfillm ent of the requirements for the degree of Doctor of Philosophy at Ohio State University. Agricultural Experiment Station, University of Arkansas College of Agriculture and Home Eco­ nomics. Lippert S. Ellis, director; John W. White, associate director. Main Station, University; with Cotton Branch Station, Lee County; Rice Branch Station, Arkansas County; Fruit and Truck Branch Station, Hempstead County; and Livestock and Forestry Branch Station, Independence County. PPC3M655 The Southwestern Corn Borer in Arkansas By L. H. Rolston Department of Entomology In the brief interval following the entrance into Arkansas of the southwestern cornDiatraea borer, grandiosella Dyar, it has become a corn pest of great importance. A thorough investigation of its biology and possible control measures was necessitated by the rapidity with which the borer has spread and the resulting crop damage. R eduction of yield arises in several ways. Young plants may be killed or dwarfed by borer activity in the stem; the yield may be reduced by extensive tunneling in the stalk; and mature grain may be lost as a result of fall girdling activity. Heavy infestations in sweet corn ears, although infrequent, are disastrous to the grower when they occur. Relatively little has been published about the southwestern corn borer in spite of its economic importance and of its having been in the United States for many years. The first comprehen­ sive investigation was that of Davis and his co-workers in New Mexico and Arizona (2). More recent bulletins have been issued by Kansas (15) and Oklahoma where particular attention has been paid to the development of cultural control practices (14). Since Arkansas differs considerably in climate and topography from the locales of previous investigations, there was no assurance that the seasonal history of the borer would parallel that in neigh­ boring states nor that cultural practices recommended there would be effective under Arkansas conditions. The biology of the borer has been given particular attention during this investigation. The habits of both the larva and adult have been studied to ascertain the possibilities they offer for control as well as the limitations they impose. Previously sug­ gested cultural control measures have been evaluated under local climatic conditions. REVIEW OF LITERATURE Diatraea Species in the United States The genus Diatraea contains a large number of species but nearly all are confined to tropical and subtropical regions. Sev­ eral species are im portant pests as borers in cultivated grasses, particularly sugar cane and corn. DiatraeaOf the speciessix known from the United States, three are apparently rare and of no economic importance:D. evanescens Dyar, D. lisetta (D yar), andD. venosalis (D yar). 4 A rkansas E xperiment Station, B ulletin 553 The sugar cane borer,saccharalis D. (Fabr.), is well known as a pest of both sugar cane and corn. It is found along the Gulf Coast of Texas, Louisiana, and Mississippi and in the southern half of Florida. Thesouthern corn stalk borer,D. crambidoides (Grote), is capable of damaging corn severely but is not consistently a major pest. Its range extends from Maryland to Florida and apparently westward into Kansas, but heavy populations are confined to the southeast. This species is widely known under D.the synonym zeacolella Dyar. Thesouthwestern corn D.borer grandiosella Dyar concludes the list of knownDiatraea species from the United States. The damage caused by this insect and its range are discussed in detail under appropriate sections. Y e t another species,D. lineolata (Walker) has been errone­ ously reported from the southwest. U n til 1911 D. saccharalis (Fabr.) was believed to be the sole representative of the genus in the United States and all papers and records on the southern corn stalk borer and southwestern corn borer, as well as the sugar cane borer, were published under this name. In that year Dyar published a revisionDiatraea of the based on the color and external morphology of the adult (5), but the characters used have proved insufficient to consistently sep­ arate all the species. The main impact of this paper on economic literature was the establishment of the southern corn stalk borer, underD. zeacolella D yar, as a species d istin ct fro m the sugar cane borer of southern Florida and the Gulf coast. Holloway later gave a method for separating the larval forms of these two species by means of the setal pattern (7). In Dyar’s revision, the southwest­ ern corn borer was described as a new species fromD. Mexico and lineolata (Walker) was redescribed from specimens from Mexico and a single specimen from Arizona. This latter specimen was un­ doubtedly D.not lineolata (Walk.) but the southwestern corn borer, for the northern D.lim lineolata it for (Walk.) is now known to be central Mexico (1). Therevision of Dyar and Heinrich in 1927 has done much to clear up the confusion concerning theDiatraea identity species of (6). As a result of these authors’ detailed study of the genitalia for diagnostic purposes there was a complete change in species concepts, many names being reduced to synonymy and others rec­ ognized as valid. References toDiatraea species prior to 1927, and particularly those before 1911, must be regarded critically. Sometimes the T he Southwestern Corn B orer in Arkansas 5 identity of the species involved can be deduced from the locality. Adequate descriptions of habits, damage, and eggs are of great help. Of the three commonDiatraea the sugar cane borer is the only species not habitually overwintering in the stalk base below soil level. The eggs of the southwestern corn borer are distinctive, having three red bars that the eggs of the other two species lack, and the larva’s habit of girdling the stalk near ground level in the fall is unique. F or a technical description of AmericanDiatraea, along with excellent drawings of the genitalia, the reader is referred to Dyar and Heinrich (6). In this paperD. lisetta (Dyar) is described and figured under the synonymlesta lisetta D yar andD. crambidoides (Grote) underD. zeacolella D yar. Thesynonymy of American species and new species, as well as photomicrographs of genitalia, are given by Box (1). History of Distribution What may be the first reference to the southwestern corn borer occurs in a note appended to a paper by L. O. Howard in 1891, stating that larvae of the sugar cane borer had been found infesting corn in two localities in New Mexico (8). These larvae were probably the southwestern corn borer, since it is the only Diatraea species normally found in this area. The distribution in 1931, as given by Davis et al, included southeastern Arizona, the southeastern two-thirds of New Mexico, most of the Panhandle and Big Bend of Texas, most of the Oklahoma Panhandle, and a few counties of southeastern Colorado and southwestern Kansas (2). No appreciable extension of this range occurred until 1941, when the borer resumed its easterly advance across Oklahoma and north­ erly advance across Kansas. The borer spread across Kansas quite rapidly, reaching a few counties in south central Nebraska in 1945 (15). A survey in the fall of 1950 showed the northern lim it of the borer’s range to have receded from Nebraska and the northern third of Kansas but the eastern lim it to have advanced across Okla- homa into west central Arkansas and the southwestern corner of Missouri (13). In 1954 the borer was again present in all but five northwest­ ern and two northeastern counties of Kansas (9). In Missouri, 10 southwestern counties were infested in 1953 and 25 counties in 1954 (12). There are apparently two principal areas of infestation in Texas; one in the northeast corner involving 15 counties and probably as many as 25, and the other in the Panhandle covering 13 counties and probably 28 (4). It is apparent that the distribu­ tion of the borer has been fluid, with a considerable easterly