Toxicity of the active fraction of Pergularia tomentosa and the aggregation pheromone phenylacetonitrile on Schistocerca gregaria fourth-instar nymph: effects on behavior and acetylcholinesterase activity

Abstract

Chemical insecticides remain the most used approach in locust control although they present a serious menace to human health and the environment. The search for alternative control methods, efficient and environmentally friendly, has become indispensable. The aim of this work is to study the effect of the aggregation pheromone, phenylacetonitrile, alone or in combination with the active fraction of Pergularia tomentosa on Schistocerca gregaria fourth-instar nymph. Toxicity bioassays showed that the combination of phenylacetonitrile with the active fraction of P. tomentosa significantly increased nymph mortality. Results also showed that the aggregation pheromone caused significant mortality especially after 6 hours of exposure. The pheromone also caused neurotoxic effects on S. gregaria nymph due to the disturbance of the acetylcholinesterase activity. We also noted the presence of cannibalism phenomenon. Phenylacetonitrile seems to have an effect on phase ployphenism of S. gregaria imagos that exhibit specific traits to the solitarious phase.

Keywords

• Behavior
• botanical insecticide
• desert locust
• enzyme
• pheromone