Formulação emulsionável de sementes de Annona muricata L. (Annonaceae) sobre Planococcus citri (RISSO, 1813) (Hemiptera: Pseudococcidae) e seletividade a coccinelídeos

Abstract

Planococcus citri is an exotic, cosmopolitan and polyphagous pest. This mealybug is widespread in almost all Brazilian states, causing direct and indirect damage to economically important crops such as citrus, grapevine and coffee. There are no insecticides registered to control this pest. In this sense, there is a need to seek alternative methods to control these. The plants of the Annonaceae family are promising in the control of agricultural pests, as studies show that in addition to being efficient in the control of agricultural pests, they are selective to natural enemies. Another advantage of the control with botanical extracts is being able to associate it with other methods, especially the biological control. Predatory ladybugs are voracious natural enemies of mealybugs. Cryptolaemus montrouzieri and Zagreus bimaculosus are ladybug predatory ladybugs in all stages of life. In this context, the objective of this work was to formulate an emulsion based on ethanolic extract of soursop seed, to test its lethality to third instar nymphs and adults of P. citri and to verify its selectivity to third instar larvae and adults of ladybugs C. montrouzieri and Z. bimaculosus. For the formulation of the emulsifiable extract, different amounts of Span® and Tween®, distilled water and ethanolic soursop extract were used. Third-instar nymphs and adults of P. citri were used for the bioassays.Tests were performed by contact, with residue and with systemic action of the emulsifiable extract. To verify the selectivity, bioassays were carried out with third instar larvae and adults of the two species of ladybugs, where tests were carried out by contact, residue and ingestion of food treated with the lethal concentrations stipulated for the mealybugs. When applied by contact on scale insects, it was possible to estimate the lethal concentrations LC50 and CL99 for nymphs (0.73% and 5.55%) and for adults (9.46% and 26.04%). Systemic action was observed when the extract was added to the soil, with increased mortality of nymphs and adults as the concentrations increased. The extracts proved to be selective to the larvae and adults of the two ladybug species in all application methods. It is concluded that the emulsifiable extract of soursop has both contact and systemic action, by application via soil. On the other hand, it has no systemic effect via leaf, nor residual effect for mealybugs. The extract proved to be selective for the two ladybug species.