Sublethal and lethal effects of different residues of spinosad on Pardosa spiders.

Spinosad is one of the world's most widely applied natural bioinsecticides and its use has been growing rapidly in the past decade. Biologically based plant protection products can also have unexpected effects on beneficial arthropods. Previous studies examining the lethal and sublethal effects of spinosad on different groups of spiders have shown widely diverging results. This work aims at an extension of knowledge related to the effects of spinosad on the generalist predator of genus Pardosa. We focused on the effects of fresh wet, fresh dry, and dry 3-day-old residues of the commercial plant protection product Spintor®. We examined changes in predatory activity at different prey densities after contacts with those residues and also on the mortality of spiders. For the density of six prey (flies), we found differences in spiders' predatory activity in the short term and the long term after their 1 hr contact with fresh wet residue. The fresh wet residues significantly decrease the number of killed flies. There was no significant effect of treatment on the mortality of spiders over short periods. Over long periods, the fresh wet residues caused a significant increase in spider mortality while dry residue had no effects.