Effects of some chemical and biological insecticides on beet armyworm (Spodoptera exigua Hubner (Lepidoptera: Noctuidae)) and natural enemies in sugar beet fields

Beet armyworm Spodoptera exigua (Lepidoptera: Noctuidae), is an important pest that feeds on various crops worldwide. It has many natural enemies including Chrysoperla carnea Stephens and Coccinella undecimpunctata L. (Coleoptera: Coccinellidae). The chemical control of this pest causes environmental pollution, destruction of natural enemies and threatens human health. Therefore, selection and use of non-destructive and safe pesticide is essential. In the present study, the efficacy of four pesticides i.e. spinosad with concentration 200 ml ha(-1), emamectin benzoate 200 g ha(-1), SeMNPV 5x10(8) OB mL(-1) and Btk 1 kg ha(-1) in controlling larval stages of S. exigua at 1, 3, 7, 14 and 21 days after treatment in a sugar beet field were evaluated. The mortality of larval and adult stages of two predators, C. undecimpunctata and C. carnea, were also assessed. The highest efficacy in controlling the larval stage of S. exigua was observed in the emamectin treatment. The lowest efficacies were observed in the Btk and SeMNPV treatments, while spinosad had a moderate efficacy. The mortality of larvae and adults of both the predator species were highest in the emamectin treatment. Btk and SeMNPV had the least negative effects on the population of the predators, these two treatments were not significantly different. Spinosad caused a moderate mortality in population of the predators. In the damage assessment on plants, the highest and lowest percentages of damage were observed in the SeMNPV virus treatment and emamectin. Spinosad and emamectin, are recommended as the most effective compounds to control larvae of S. exigua, while SeMNPV and Btk are recommended for integrated pest management and are safe to the natural enemies.