Performance of Cry1Ab‐susceptible and ‐heterozygous resistant populations of sugarcane borer in sequential feedings on non‐Bt and Bt maize plant tissue

Abstract

AbstractA seed mix strategy has been used to provide refuge to susceptible insects for resistance management in planting transgenic maize expressing Bacillus thuringiensis Berliner (Bt) proteins. To determine whether larval movement in a seed mix planting creates favorable conditions for resistant heterozygotes of a target pest, performance of Cry1Ab‐susceptible (SS) and ‐heterozygous resistant (RS) populations of the sugarcane borer, Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae), was evaluated in sequential feeding on non‐Bt and Cry1Ab (event MON 810) maize plant tissue. For each insect population, nine feeding sequences were employed. SS and RS feeding on non‐Bt plants for their entire larval stages survived well and >60% of the adult pairs produced viable eggs, with an average of 269 progeny per female, whereas none of the two populations on Bt maize plants survived to the pupal stage. SS larvae could not develop to adults if the larvae fed on non‐Bt plants for ≤15 days and then moved to Bt plants. In contrast, 4.2–29.2% of RS larvae that fed on non‐Bt plants for ≥9 days and then moved to Bt plants developed to adults, and 63.6% of pairs of these adults produced viable eggs, with an average of 185 progeny per female. For SS larvae that fed on Bt plants for 1 or 2 days and then moved to non‐Bt plants, few larvae developed to adults with varied emergence times, whereas 28.1 and 13.5% RS larvae feeding on Bt plants for 1 and 2 days, respectively, successfully developed to adults; 43.8% of pairs of these adults produced viable eggs, with an average of 220 progeny per female. For the case of the single Bt gene maize plants (event MON 810), the results suggest that RS insects may have advantages in survival and reproduction over SS if RS larvae hatch and feed on Bt plants during the first 1 or 2 days and then move to non‐Bt plants. This advantage is less for RS larvae that hatch and feed on non‐Bt plants first and then move to Bt plants, unless the larval movement occurs in the later stages (e.g., fourth or fifth instars).