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Title: EXTREME SUSCEPTIBILITY OF HIBANA FUTILIS SPIDERLINGS TO SELECTED INSECTICIDES IN A LABORATORY BIOASSAY.

Author
item Elzen, Gary
item Pfannenstiel, Robert

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2009
Publication Date: 3/1/2009
Citation: Elzen, G.W., Pfannenstiel, R.S. 2009. Extreme susceptibility of Hibana futilis spiderlings to selected insecticides in a laboratory bioassay. Southwest. Entomol. 34(1):103-106.

Interpretive Summary: Pesticides may affect beneficial arthropods in many ways and remain an important component of integrated pest management systems. A search of the relevant literature on the susceptibility of spiders to pesticides showed that few studies have been done. We decided to examine the toxicity of 5 commonly used insecticides to one particularly abundant spider, Hibana futilis Banks, which was easily collected in large numbers. We used a standard bioassay to determine concentration-mortality relationships among insecticides representative of organophosphates, pyrethroids, carbamates, chloronicotinyls, and spinosyns. Test organisms were obtained by collecting egg sacs of H. futilis in the field. Results showed that we could not find a dose of any insecticide that did not produce 100% mortality of the spiders. Our methods showed that H.futilis was intolerant to doses of insecticides that were one thousand times less than that shown in the literature. Caution should be used when attempting to preserve beneficial spiders in agriculture.

Technical Abstract: Hiburna futilis Banks spiderlings were used to determine the toxicity of commonly used insecticides. We used a standard insecticide residue bioassay to determine concentration-mortality relationships among the insecticides malathion, cyfluthrin, methomyl, imidacloprid, and spinosad. Test organisms were obtained by collecting egg sacs in the field. These were taken to the laboratory and allowed to emerge. Spiderlings were subjected to the bioassay for 24 h. We found that all concentrations used caused 100% mortality of the spiderlings. Concentrations as low as 5 x 10-74 micrograms caused 100% mortality to all insecticides. We concluded that H. futilis was extremely sensitive to insecticides and this should be considered in integrated pest management programs.