1998 ESA North Central Branch Meeting Abstract
67 UV PROTECTION OF BACILLUS THURINGIENSIS WITH LIGNIN BASED FORMULATIONS. R. W. Behle1, M. R. McGuire1, B. S. Shasha2, P. T. Tamez-Guerra3, and R. L. Pingel2. 1USDA-ARS, 1815 N. University, Peoria, IL 61604; 2Department of Biology, Olin Hall, Bradley University, Peoria, IL 61625; 3FCB-UANL, Monterrey, N. L., Mexico 6400
Ultraviolet (UV) light is considered major factor in the loss of activity when biological pesticides are applied in the field. Ingredients added to new formulations have the potential to improve the residual insecticidal activity of biopesticides by absorbing or reflecting damaging wavelengths of sunlight. Lignin is a natural aromatic organic polymer extracted from woody plants and is a suitable ingredient to prevent photo degradation. Preliminary measurements showed that dilute solutions (0.1% w/v) of lignin effectively blocked 98% of the light energy between 300 to 400 nm from a xenon light source. We developed experimental formulations of Bacillus thuringiensis (Bt) in an effort to improve the residual insecticidal activity of biopesticides. Loss of spore viability and insecticidal activity when exposed to the xenon light was determined for experimental formulations and unformulated Bt based on a paired design which compared exposed samples with unexposed samples. Unformulated Bt exposed for 40 minutes lost 99% spore viability determined by plating and 75% insecticidal activity determined by a droplet assay with European corn borer, Ostrinia nubilalis (Hübner). In the same experiment, Bt formulated with lignin in solution lost only 39% spore viability and 23% of its insecticidal activity. Spray drying lignin creates a sprayable-powder formulation with a close association between Bt and lignin. In laboratory assays, this formulation had more viable spores after exposure to xenon light than technical Bt or the commercial formulation Dipel 2X. The spray dried lignin formulation showed a similar loss of activity compared with Dipel 2X when applied to field grown cabbage and assayed with neonate cabbage looper, Trichoplusia ni (Hhbner), for residual insecticidal activity 0, 1, 4, and 7 days after application. Laboratory experiments demonstrated the benefits of lignin in preventing UV degradation of Bt, however, field experiments demonstrated little improvement over the commercial formulation.
This paper will be presented on Monday.
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