Location: Pest Management ResearchTitle: Joint action of Beauveria bassiana and the insect growth regulators diflubenzuron and novaluron, on the migratory locust, Locusta migratoria) Author
Submitted to: Journal of Pest Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/24/2012
Publication Date: 2/15/2013
Publication URL: handle.nal.usda.gov/10113/58597
Citation: Bitshadze, N., Jaronski, S., Khasdan, V., Abashidze, E., Abashidze, M., Latchininsky, A., Samasdashvili, D., Sokhadze, I., Rippa, M., Ishaaya, I., Horowitz, R. 2013. Joint action of Beauveria bassiana and the insect growth regulators diflubenzuron and novaluron, on the migratory locust, Locusta migratoria. Journal of Pest Science. 86(2):293–300. DOI: 10.1007/s10340-012-0476-4. Interpretive Summary: While insect pathogenic fungi have been developed for the control of grasshoppers and locusts, these pathogens are subject to the criticism that they act too slowly and require too high rates to be practical. One measure for improving efficacy is to combine fungi with sublethal amounts of a chemical pesticide, which would act as a stressor increasing an insect’s susceptibility to the pathogen. A prime candidate pesticide are the insect growth regulators that inhibit chitin formation after immature insects molt to the next stage – diflubenzuron and novaluron. These compounds are registered for use against grasshoppers. Past literature on the subject has been inconclusive, however, about their ability to synergize an fungal pathogen. In the present study several low rates of both compounds were applied either simultaneously or sequentially with a low dose of the commercial fungus Beauveria bassiana Strain GHA, which is registered for use against grasshoppers in the U.S., but is normally too expensive to use by itself at recommended rates. Existence of synergistic, additive, or antagonistic interactions of these combinations was assessed with a simple statistical analysis. Most interactions were merely additive, with one combination actually antagonistic for the fungus.
Technical Abstract: Beauveria bassiana (Balsamo) Vuillemin and sublethal concentrations of the insect growth regulators (IGR) diflubenzuron and novaluron were applied simultaneously and sequentially to second instar Locusta migratoria migratorioides (Sauss.) to determine the interaction between these materials and an entomopathogenic fungus. Nymphs were fed on corn leaf discs treated with several concentrations of each IGR, and a constant dose of B. bassiana was applied topically. Additive interaction was demonstrated in all instances when second instar nymphs were exposed to diflubenzuron or novaluron simultaneously with B. bassiana treatment, and when the fungus was applied first and either IGR applied after 48 h. Additive interaction was also exhibited when novaluron was applied first and B. bassiana was applied after 48 h. Antagonism was demonstrated when nymphs were fed diflubenzuron-treated corn leaves treated with diflubenzuron and after 48 h were treated with B. bassiana 48 hr later.