Repellency and insecticidal activities of <i>Thapsia garganica</i> crude extract against some important pests

Abstract

Repellency and insecticidal activities of Thapsia garganica leaf methanolic extract were investigated against Tribolium castaneum, Myzus persicae, Phthorimaea operculella, and Spodoptera littoralis. Repellency and toxic activities (by ingestion and topical application) were evaluated on T. castaneum nymphs and adults. Topical application treatment caused total larval growth inhibition at 10%, until mortality after 7 days. The highest mortality was recorded with 94% at the same concentration. Methanolic extracts incorporation into T. castaneum larvae artificial diet at 10% caused 100% mortality after 3 days. The extract at 1% cause high repellent effect on T. castaneum after 60 min of exposure, while M. persicae was less sensitive. P. operculella female’s showed sensitivity by a repellent effect at oviposition. Egg’s number laid on treated tubers at 1% and 2% decreased significantly to 32% and 72%, respectively. In addition, methanolic extracts had a preventive effect on P. operculella larval penetration. In fact, the number of larvae was reduced by 30.46% and 76.12% in the treated tubers at 1% and 2%, respectively. For S. littoralis, a low antifeeding effect was recorded. However, the relative growth rate (RGR), conversion of ingested and digested food to biomass, were decreased. The approximate digestibility increased. Moreover, a delay in larval development was observed. This study suggests that the leaf extract of T. garganica could be applied as bio-insecticide.