Submitted to: Ostrinia International Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 10, 1997
Publication Date: N/A
Technical Abstract: Bacillus thuringiensis Berliner (Dipel ES, potency of 16.8 x 10**9 International Units (IU)/1) was applied to corn plants at 6.6 and 8.7 x 10**9 IU/ha. Plants were infested with O. nubilalis larvae on the same day as B. thuringiensis application and others 1, 2, 4, 8, and 12 d after application. Evaluations were made by counting the number of live larvae in the whorl of the plant, the number of B. thuringiensis spores in the whorl of the plant, the larval mortality from B. thuringiensis crystals taken from the whorl of the plant, and the cm of tunneling in the stalk 40 d after O. nubilalis larval infestation. B. thuringiensis reduced the number of live larvae per whorl by 63% and the cm of tunneling by 62%. The r values (regression analysis) were 0.65, 0.49, 0.47, 0.45, for tunneling vs. live larvae in the whorl, spores in the whorl vs. larval mortality, live larvae in the whorl vs. larval mortality, and tunneling vs. larval mortality, respectively. The r values for the relation were 0.97, 0.93, 0.97, 0.95, and 0.93, respectively, for the days after larval infestation. Counting live O. nubilalis larvae in the whorl of the plant 4-10 d after larval application is an accurate alternative to stalk splitting to determine effectiveness of B. thuringiensis in suppressing O. nubilalis larvae.