Document Type

Article

Publication Date

1-1-1999

Abstract

The relative susceptibility of different instars of the European corn borer, Ostrinia nubilalis (Hubner), to a commercial formulation of Bacillus thuringiensis Berliner subsp. kurstaki, Dipel ES, was determined using diet incorporation. European corn borers exposed to Dipel during the 1st instar were much more susceptible than were older larvae. No significant differences in susceptibility were found among 3rd, 4th, and 5th instars at doses of 0.03-0.81 ml of Dipel per kilogram of diet. At high concentrations (2.43 ml/km of diet), 5th instars had significantly lower mortality than did 3rd or 4th instars. The LC50 and LC90 of the 5th instars were 98.1- and >168.2-fold higher, respectively, than those of 1st instars. These findings should be accounted for during the development of a resistance management strategy for the use of B. thuringiensis toxin as a microbial insecticide and possibly, for Bt-expressing transgenic corn. Differential susceptibility of different instars of European corn borer to B. thuringiensis suggests that the 'ultra high-dose' or 'high-dose' resistance management strategy should be defined in terms of the largest and the least susceptible stage, because larvae may have opportunities to grow and develop on non-Bt-corn or alternate hosts before they attack the Bt-corn plants.

Publication Source (Journal or Book title)

Journal of Economic Entomology

First Page

547

Last Page

550

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