Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 2008
Publication Date: December 31, 2008
Citation: Williams, W.P., Buckley, P.M. 2008. Fall Armyworm (Lepidoptera: Noctuidae) and Southwestern Corn Borer (Lepidoptera: Noctuidae)Leaf Feeding Damage and Its Effect on Larval Growth on Diets Prepared from Lyophilized Corn. Journal of Agricultural and Urban Entomology. 25:1-11. Interpretive Summary: Fall armyworm and southwestern corn borer are major pests of corn in the southern United States. These insects attack corn plants in both the vegetative and reproductive stages of growth, and their feeding can result in substantial losses. Transgenic BT hybrids have been successfully used to reduce damage to these insects. Corn hybrids with naturally occurring resistance can be used as an alternative to transgenic BT hybrids or to complement them in pest management strategies. USDA-ARS scientists have developed and released corn germplasm with resistance to fall armyworm, southwestern corn borer, and other Lepidoptera. To most effectively use this germplasm in developing corn hybrids, it is necessary to understand the interaction between the plant and the insect. Bioassays were conducted to determine the effects of larval feeding on plants in the field on larval growth on freeze dried tissue in the laboratory. Both fall armyworm and southwestern corn borer larvae weighed more when fed on freeze dried tissue of susceptible plants than resistant plants. Larvae reared on tissue that had been fed on in the field were smaller than those reared on tissue from non-infested plants. Larval feeding apparently induces defensive measures in corn plants. This information will aid in identifying genes that affect larval feeding which will help in development of insect resistant corn hybrids.
Technical Abstract: Fall armyworm, Spodoptera frugiperda (J. E. Smith), and Southwestern corn borer, Diatraea grandiosella Dyar, are economically important pests of maize (Zea mays L.) in the southeastern United States. These insects attack plants in both the vegetative and reproductive stages of growth. Plant resistance is widely considered a desirable means for reducing losses to both insects, and corn germplasm lines with resistance to leaf feeding damage have been developed and released. Fall armyworm and southwestern corn borer larvae feeding on resistant genotypes grow more slowly than those feeding on susceptible genotypes. The objectives of the investigation were to evaluate 20 single cross maize hybrids for leaf feeding damage by southwestern corn borer and fall armyworm, to compare larval growth on laboratory diets prepared from lyophilized leaf tissue of single cross hybrids with different levels of resistance to leaf feeding, and to determine whether larval growth differed between diets prepared from leaf tissue collected from plants previously infested with southwestern corn borer or fall armyworm and non-infested plants. Both fall armyworm and southwestern corn borer larvae weighed significantly less when fed on laboratory diets prepared from lyophilized leaf tissue of resistant single cross hybrids than susceptible hybrids. When tissue from either resistant or susceptible plants that had been infested with either insect in the field was used in bioassays, larval weights were further reduced. It appears that both constitutive and induced defensive mechanisms may be operating.