ARS | Publication request: Control of mosquitoes in catch basins in Connecticut with Bacillus thuringiensis israelensis, Bacillus sphearicus, and Spinosad

Submitted to: Journal of the American Mosquito Control Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 2, 2010
Publication Date: March 1, 2011
Citation: Anderson, J.F., Ferrandino, F.J., Dingman, D.W., Main, A.J., Andreadis, T.G., Becnel, J.J. 2011. Control of mosquitoes in catch basins in Connecticut with Bacillus thuringiensis israelensis, Bacillus sphearicus, and Spinosad. Journal of the American Mosquito Control Association. 27(1):45-55.

Interpretive Summary: Mosquitoes are important vectors of diseases to man and animals and new control strategies are being investigated. In this collaborative research project between ARS scientists at the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL, and researchers at the Connecticut Agricultural Experiment Station, New Haven, CT, the effectiveness of several commercial products in controlling juvenile mosquitoes developing in catch basins in Stratford, CT during the summers of 2008 and 2009 were evaluated. It was determined that even with relatively large numbers of larvae hatching almost every day two applications of VectoMax may be relatively effective in suppressing Culex adults and reducing human risk of exposure to West Nile virus. In addition, a single application of Natular XRT tablet containing 6.25% spinosad showed that larvae were significantly reduced for five weeks in catch basins. This study suggests that spinosad may be useful in controlling mosquitoes in catch basins, but further study is needed to evaluate frequency of application during summer, efficacy of different formulations, and the most effective application rates.

Technical Abstract: Catch basins are a major source of Culex pipiens pipiens, Cx. restuans, and Aedes japonicus in northeastern U.S. VectoBac CG®, VectoLex CG®, and VectoBac 12AS® applied at maximum label rates to catch basins in Stratford, CT on June 30 and July 28, 2008 significantly reduced numbers of larvae for one week. When applied at three times the maximum label rate on August 18, VectoLex CG®, VectoBac 12AS®, and VectoBac CG® significantly reduced numbers of larvae for 5, 4, and 2 weeks, respectively, compared to the untreated controls. A single application of VectoMaxTM WSP on August 1, 2008 significantly reduced numbers of 3rd and 4th instar larvae and healthy pupae through August 21, but numbers of large instars in treated catch basins at 21 days post-treatment had increased to 40% of the numbers in untreated controls. A second treatment applied on August 22 reduced numbers of large instars and healthy pupae to near zero into mid September. In 2009, VectoMaxTM WSP applied on July 1 significantly reduced numbers of large instars and healthy pupae for two weeks, but thereafter, although mean numbers of larvae and healthy pupae remained lower throughout the summer, differences between the treated catch basins and untreated ones were sometimes non-significant. Numbers of large instars and pupae were significantly reduced following the second application of VectoMax on August 18 and remained so throughout the end of September. A second application of VectoMax to catch basins is likely needed during summer to keep numbers of Culex and Ae. japonicus significantly reduced to lower risk of human exposure to WNV. The application of one Natular XRT tablet to individual catch basins on July 22, 2009 significantly reduced total numbers of larvae for five weeks through August 24.