Efficacy of Libidibia ferrea var. ferrea and Agave sisalana Extracts against Dactylopius opuntiae (Hemiptera: Coccoidea)

The carmine cochineal (Dactylopius opuntiae) is an insect-plague of Opuntia ficus-indica palm crops, causing losses in the production of the vegetable used as forage for the Brazilian semiarid animals. The objective of this work was to analyze the efficacy of plant extracts, insecticides and their combination in the control of D. opuntiae. Leaf and pod extracts of Libidibia ferrea var. ferrea, Agave sisalana leaf at concentrations 10, 25, 50, 100 and 200 mg/mL, and insecticides (chlorpyrifos, acetamiprid, thiamethoxam and lamba-cyhalothrin) at concentrations minimum, median and maximum; were applied on cladodes infested by D. opuntiae. After 10 days of treatment, the percentages of mortality and LC50 (concentration to kill 50% of cochineal) were obtained on the stages of nymphs II and adult females. The association between the LC50 of the plant extracts with the insecticides on the cochineal it was tested. The results showed that L. ferrea extracts were more effective against cochineal, causing the 81% of nymphal II mortality (LC50: 20 to 160 mg/mL) and 97% of adult females (LC50: 43 to 50 mg/mL), whereas the extracts of A. sisalana only controlled adult females, causing the mortality from 51 to 97% (LC50: 17 to 46 mg/mL). The insecticide chlorpyrifos was the most efficient on nymphs and adult females cochineal (LC50: 0,084 mL/L). The combination of this insecticide with the extracts promoted a percentage of mortality above 90%. The extracts presented insecticidal potential on D. opuntiae and can be tested isolated or in combination with insecticides in control of cochineal.