Bioactivity of Piper aduncum and Piper marginatum essential oils on Planococcus citri (RISSO, 1813) (Hemiptera: Pseudococcidae)

The mealybug Planococcus citri (Risso, 1813) is an important pest of several crops. However, control is difficult because of the waxy layer that protects the body, so farmers resort to systemic insecticides, which increases production costs. This study aimed to evaluate the activity of P. aduncum and P. marginatum essential oils on P. citri, through bioassays of topical toxicity in migratory nymphs; residual toxicity in migratory, second instar nymphs and adult females; and repellency. Azamax^® was used to compare the results. The LC’s50 values estimated through the concentration-response curve for P. aduncum oil were 2.85 μl/mL for the topical test in migratory nymphs, and 1.83 and 1.50 μl/mL for the residual test in nymphs migratory and second instar, respectively. The LC’s50 for P. marginatum oil were 2.36 μl/mL for the topical test on migratory nymphs, and 2.28 and 3.81 μl/mL for the residual test on migratory and second instar nymphs, respectively. CL’s30 and 50 (topical test on first instar nymphs) tested on females caused low mortality and the results were similar between treatments. However, low concentrations of the oils had effects on the waxy layer of the pest. In the repellency test it was possible to verify that the LC10 of P. aduncum was more repellent than the LC10 of P. marginatum. The oils were promising for P. citri, and more studies are needed.