Entomology, Department of


Date of this Version



Published in Journal of Economic Entomology Volume 93, Issue 3 (June 2000) pp. 925–930. Copyright 2000 Entomological Society of America. Used by permission.


Two candidate diagnostic concentrations of the Cry1Ab and Cry1Ac toxins from Bacillus thuringiensis corresponding to the LC99 and EC99 (effective concentration that causes 99% growth inhibition) for European corn borer, Ostrinia nubilalis (Hubner), were determined based on previously obtained baseline data. Validation experiments using field-collected European corn borer populations from across North America showed that for Cry1Ab, a concentration corresponding to the upper limit of the 95% confidence interval of the LC99, produced mortality .99% for all populations tested. However, for Cry1Ac, adjustments and further validation are probably necessary. Development of B. thuringiensis resistance monitoring programs that rely on diagnostic techniques are discussed.

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