Residual activity of abamectin and spinosad against the predatory bug Orius laevigatus

The residual effect of two biopesticides, abamectin and spinosad, on the predatory bug Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) was tested using a laboratory and an extended laboratory method. Experiments were conducted in the spring and summer 2000. The LD(50)s on the 2nd and 5th nymphal instar and the adult stage, were lower for abamectin than for spinosad. The toxicity of each product,on the 2nd instar and adults was significantly greater than on the 5th nymphal instar. Abamectin was much more persistent in spring than in summer. Spray deposits (at the recommended rate of 10 ppm a.i. for leaftniner control) were toxic for 1 month in spring, whereas in summer they were no longer toxic after 2 weeks. Spinosad summer spray deposits (recommended rate of 250 ppm a.i. for leafminer and caterpillar control) were not toxic after 5 residual days.