Toxidade residual de Acetamiprido + Piriproxifem sobre Apis mellifera (Hymenoptera: Apidae).

Abstract

The honey bees (Apis mellifera) are essential pollinator for several crops, such as the melon (Cucumis melo L.). However, the excessive use of insecticides may harm several pollinators. Therefore, this work aims to evaluate the lethal and sublethal effect of the insecticide Acetamiprid + Pyriproxyfen on honey bees through residual contact on melon leaves as a function of different times after spraying the insecticide. The work was carried out at the Entomology Laboratory of CCTA/UFCG, Campus Pombal. The insecticide effect was investigated in a completely randomized design, in a 4 X 3 factorial scheme, two doses of the product: (1) the minimum dose of 200mL/ha (0.08 g a.i./L of Acetamiprid + 0.04 g a.i./L of Pyriproxyfen); (2) the maximum dose of 300mL/ha (0.12 g a.i./L of Acetamiprid + 0.06 g a.i./L of Pyriproxyfen) recommended for application in the melon crop; (3) thiamethoxam at the dose of 600 mL/ha (0.3 g a.i./L) as positive control; and (4) distilled water as absolute control; all submitted to three different exposure times (1, 2, and 3 hours after spraying). After exposure, bees’ mortality was recorded at 1, 2, 3, 4, 5, 6, 12, 24, and 48 hours after the start of insecticide exposure on leaves. Bees’ behavior (prostration, tremors, paralysis, etc.) were monitored at each assessment time. The flight abilities of the survivors were examined after 48 hours of contact with the products. The minimum dose within 1h after application and the maximum dose at 1h, 2h, and 3h showed mortality of 40%, 48%, 45%, and 39%, respectively. The minimum dose at 2h and 3h after application showed no significant difference, and caused the lowest percentage of mortality, 20%, which is considered moderately toxic to honey bees compared to a positive control. Regarding the behavior, it was verified that the bees clustered in the center of the arenas, regardless of the dose, and some individuals were more active with greater motor activity and flapping their wings without being able to climb the wall and reach the ceiling. Acetamiprid + Pyriproxyfen at the tested doses is moderately toxic to adult workers of honey bees in residual contact with melon leaves. Despite the low mortality compared to the positive control, it caused motor disorders and reduced light flight capacity.