Insecticidal activity of some plant essential oils against the Opuntia cochineal scale insect, Dactylopius opuntiae Cockerell (Hemiptera: Dactylopiidae)

Opuntia ficus-indica (L.) is largely cultivated in Morocco because of its remarkable adaptation to arid and semi-arid climates and significant economic importance. However, in recent years, a severe invasion of these species plantations by Dactylopius opuntiae has been detected in many regions in Morocco. The present study evaluates under laboratory conditions the toxicity of some Moroccan plant essential oils (EOs) against the mobile stages (adult males and crawlers) of D. opuntiae in direct contact and fumigation bioassays. All EOs tested were found to be toxic to adult males and crawlers of D. opuntiae , but with variable degrees . Thymus vulgaris EO exhibited the highest activity against adult males in both contact and fumigation assays. EOs obtained from Mentha suaveolens subsp. timija , Chenopodium ambrosioides , Mentha piperita , Myrtus communis and Laurus nobilis expressed a moderate activity. Rosmarinus officinalis displayed relatively the weakest insecticidal effect. The results suggest that these EOs, particularly those obtained from T. vulgaris and C. ambrosioides , could present potential plant-based insecticidal agents against this prickly pear cactus pest.