Insecticidal Activities of Atriplex halimus L., Salvia rosmarinus Spenn. and Cuminum cyminum L. against Dactylopius opuntiae (Cockerell) under Laboratory and Greenhouse Conditions

Abstract

Simple SummaryThe wild scale insect Dactylopius opuntiae is one of the major insect pests of prickly pear Opuntia ficus-indica (L.) in Morocco. The present study investigated the insecticidal potential of the aqueous and hydroalcoholic extracts of Atriplex halimus (leaves), Salvia rosmarinus (leaves), and Cuminum cyminum (seeds) to control nymphs and adult females of D. opuntiae under laboratory and greenhouse conditions. Among the tested samples, the aqueous extract of A. halimus showed the highest activity on nymphs and adult females of D. opuntiae in the laboratory and when combined with black soap under greenhouse conditions. The difference in toxicity of the plant species in the study was correlated with their saponin content. These results provide evidence that the aqueous extract of A. halimus leaves could be incorporated into the management of the wild scale insect as an alternative to chemical insecticides.The wild cochineal Dactylopius opuntiae (Hemiptera: Dactylopiidae) is one of the major insect pests of the prickly pear Opuntia ficus-indica (L.) in Morocco, a well-known fruit and vegetable crop of arid and semi-arid regions around the world. The present study investigated the insecticidal potential of six extracts (three aqueous and three hydroalcoholic (MeOH/H2O, 20/80 (v/v)) from Atriplex halimus (leaves), Salvia rosmarinus (leaves) and Cuminum cyminum (seeds) to control nymphs and adult females of D. opuntiae under laboratory and greenhouse conditions. Out of the tested samples, A. halimus aqueous extract showed the highest activity, inducing mortality rates of 67.04% (after 4 days) and 85% (after 8 days) on nymphs and adult females of D. opuntiae, respectively, at a concentration of 5% under laboratory conditions. It also showed the highest mortality rate of nymphs with 100% (4 days after application) and 83.75% of adult females (7 days after the second application) at a concentration of 5% when combined with black soap at 10 g/L under greenhouse conditions. The difference in the toxicity of plant species of the study was correlated with their saponin content. A total of 36 of these triterpene glucosides were suggested after a comprehensive LC-MSn profiling of the most active extract, A. halimus, in addition to phytoecdysones and glycosylated phenolic acids and flavonoids. These findings provided evidence that the aqueous leaf extract of A. halimus could be incorporated in the management of the wild cochineal as an alternative to chemical insecticides.