Field resistance of Bt maize to southwestern corn borer and sugarcane borer in two irrigation regimes

Document Type

Article

Publication Date

9-1-2006

Abstract

A lepidopterous pest complex of southwestern corn borer, Diatraea grandiosella Dyar, and sugarcane borer, Diatraea saccharalis (F.), causes economic damage to field maize, Zea mays L., in the southern United States. Management of natural infestations was evaluated in irrigated and non-irrigated plots of Bacillus thuringiensis (Bt) transgenic maize hybrid expressing the insecticidal Cry1A(b) protein associated with the MON810 transformation event. Bt maize significantly (P ≤ 0.05) reduced the number of adult borer exit holes per plant, frequency of plants with adult exit holes in stalks, and frequency of plants with ear shank and cob tunneling compared to non-Bt maize regardless of irrigation regime. Ear length and grain yields were not significantly (P > 0.05) improved in the Bt hybrid compared to those in the non-Bt hybrid but were either similar or significantly (P ≤ 0.05) greater in irrigated than in non-irrigated maize. As stalk borer infestation persisted, a significant (P ≤ 0.05) increase was observed in the number of adult borer exit holes per stalk and in the number of plants affected with exit holes, ear shank tunneling, and cob tunneling in the irrigated non-Bt maize than in the non-irrigated, non-Bt maize. This suggests that irrigated non-Bt maize fields may offer a favorable environment for increased maize stalk borer infestation and survival. During the two-year study, sugarcane borer abundance increased compared to southwestern corn borer. Larvae removed from plants near crop maturity revealed a three to one predominance of sugarcane borer over southwestern corn borer. This might signal greater selection pressure on sugarcane borer in Bt maize in the southern United States. Current Insecticide Resistance Management (IRM) plans need to consider stalk borer species composition in an area and the differences in Bt susceptibility between sugarcane borer and other maize stalk-borer species to meet the high-dose IRM strategy.

Publication Source (Journal or Book title)

Southwestern Entomologist

First Page

211

Last Page

222

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