Potential insecticidal activity of extracts from 18 species of medicinal plants on larvae of Spodoptera littoralis - Short Communication

Insecticidal activity of methanol extracts from 18 species of medicinal plants was tested on 3rd instar larvae of the Egyptian cottonworm (Spodoptera littoralis). All extracts were toxic to larvae. Extracts from Ocimum basilicum, Origanum majorana, Picea excelsa and Salvia officinalis were highly toxic (LC50 - 1.7, 3.6, 4.1 and 4.7 µg/ml, respectively). Extracts from Melilotus officinalis, Pinus silvestris, Taraxacum officinalis and Achillea ptarmica were moderately toxic (LC50 - 5.6, 7.3, 8.4 and 9.1µg/ml, respectively). The relative growth rate, consumption of food and conversion efficiency of the digested food were calculated. Clear correlations were found between weight increase, quantity of ingested food, and the quantity of excrements produced during the whole assay period. These results indicate an antifeedant property of the tested extracts.