Efficacy of Single and Dual Gene Cotton Gossypium Hirsutum Events on Neonate and Third Instar Fall Armyworm, Spodoptera Frugiperda Development Based on Tissue and Meridic Diet Assays

J. Scott Armstrong, John J. Adamczyk, Jr., Shoil M. Greenberg


We evaluated mortality and developmental parameters of fall armyworms, Spodoptera frugiperda (J. E. Smith), to the single Bacillus thuringiensis (Bt) cotton trait, Bollgard® and dual Bt cotton traits (Bollgard II® and WideStrike™) by using a cotton leaf-tissue assay and by incorporating lyophilized cotton tissue into a meridic diet. Bioassays were conducted for both neonate and 3rd instars. Leaf tissue bioassays indicated that Bollgard II® and WideStrike™ are highly effective against fall armyworm neonates by causing mortality and by retarding development parameters such as larval weight, pupal duration, and time to adulthood. Bollgard® was not significantly different from non-transgenic cotton in terms of mortality or feeding, with the exception of the non-Bt (PhytoGen 425RF), which had an inherent form of resistance that is not associated with a transgenic event. Third instars evaluated with lyophilized diet bioassays were not as affected by the Bt traits to the same degree as neonates; however, larval weights were lower, and developmental parameters such as time to pupation and time to adulthood were longer. The duration of pupal development was significantly longer for 3rd instars that survived the highest dose of 5,000 µg of WideStrike™ cotton tissue. Sublethal doses for Bollgard II® and WideStrike™ were generally observed at 500 to 5,000 µg of lyophilized cotton tissue per mg of meridic diet, depending upon the variable (time to pupation, pupal duration, time to adult emergence) measured.

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