Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2002
Publication Date: 3/1/2003
Citation: DOWD, P.F., WHITE, D.G. CORN EARWORM, HELICOVERPA ZEA (LEPIDOPTERA: NOCTUIDAE) AND OTHER INSECT ASSOCIATED RESISTANCE IN MAIZE INBRED TEX6. JOURNAL OF ECONOMIC ENTOMOLOGY. 2003. v. 95(3). p. 628-634. Interpretive Summary: Insects cause hundreds of millions of dollars of damage to crops in the United States each year. Insect damage in corn, cotton, and peanuts frequently increases the levels of ear mold toxins, which limits acceptability of the products both within the United States and for export. Often combinations of different insect control strategies can provide the most effective, economical, and environmentally acceptable insect management in different crops. However, the compatibility of these control measures, especially with those that include biotechnologically improved crop varieties, has received only limited study. Our laboratory studies demonstrated that the efficacy of corn earworm biological control by a naturally occurring insect disease was not adversely affected by the enhanced production of a protein (peroxidase) introduced by biotechnological means in tobacco and tomato plants that reduced insect damage. These studies indicate two diverse biological control techniques can be effectively combined to produce more effective insect management that is potentially economical and environmentally compatible. Potential benefits include greater profits for farmers and improved food quality for consumers.
Technical Abstract: A two-year field and laboratory study investigated insect resistance of the maize (Zea mays Lo) inbred Tex6, which has previously demonstrated resistance to Aspergillus ear rot and aflatoxin production, relative to susceptible inbred B73. Field studies indicated significantly greater resistance to insect feeding of V4-V6 growth stage Tex6 plants compared to B73 plants in both years, primarily to flea beetles (Chaetonema spp.). Field studies of natural (1999) and artificial (2000) infestations of corn earworms [Helicoverpa zea (Boddie)] indicated much lower levels of kernel damage at milk stage (ca. 3-fold) and smaller surviving larvae (ca. 3-fold) in Tex6 compared to B73 ears. At harvest, similar trends in reduction of numbers of damaged kernels per ear, as well as incidence and numbers of kernels per ear symptomatically infected by Fusarium spp. were noted. Laboratory studies indicated little difference in mortality or survivor weight of caterpillars or sap beetle adults caged with milk stage kernels of the two inbreds. However, assays with silks indicated significantly greater mortality of H. zea in both 1999 and 2000, and European corn borer (Ostrinia nubilalis Hubner) in 1999 (only year tested) when fed Tex6 silks compared to B73 silks. Pollinated Tex6 silks were generally darker colored and more toxic than unpollinated silks. Thus, it is possible that commercially usable inbreds with resistance to insects, which also contribute to the mycotoxin problem through vectoring and damage, could be produced using Tex6 as a source.