Side effects of four insecticides on Harmonia axyridis eggs (Coleoptera: Coccinellidae)

MIRANDE, LUCIANA; HARAMBOURE, MARINA; SMAGGHE, GUY; REINOSO MFA; DESNEUX, NICOLAS; SCHNEIDER, MARCELA INÉS

Gante

Simposio; 66 International Symposium on Crop Protection; 2014

Argentine in 1996 for control of Myzus persicae Schultz (Hemiptera: Aphididae). This exotic species has caused negative effects to native coccinellids (e.g. displacement) and other aphidophagous predators in most countries where it has been introduced. We hypothesized that, in addition to its capacity to compete and to exhibit strong intraguild predation on natural enemies, a lower susceptibility to insecticides in H. axyridis may also contribute to the displacement of other native natural enemies. The objective of this work was to assess the toxicity of four insecticides, commonly used in vegetal crops of Argentina, on eggs of H. axyridis. Commercial compounds were tested at their maximum registered concentration for field use: Mospilan® (acetamiprid, 200 mg/l), Epingle® (pyriproxyfen, 75 mg/l), Neem‐Azal® (azadirachtin, 40 mg/l) and Glextrin® (cypermetrhin, 100 mg/l). Groups of 20‐50 48h‐old H. axyridis eggs were dipped for 10s in aqueous insecticides solutions. Three replicates were used per insecticide and all bioassays were carried out in the laboratory under controlled conditions (25±0.5°C, 75±5% RH, 16:8 L:D). Egg hatching rate, immature development time, adult emergence, fecundity and fertility of survived females were evaluated as endpoints. Pyriproxyfen and cypermethrin showed a strong toxicity on the predator: no egg hatching was observed. On the other hand, larvae emerged in the acetamiprid treatment but 100% mortality was observed during the first 24 h. Although some larvae from azadirachtin treatment survived and reached the adult stage, a reduction in the accumulated survival (from egg to adult stage) was observed. In addition, the length of first and second larvae instars was reduced by the botanical insecticide. In contrast, it increased the length of the third and fourth larvae instars. Females? fecundity was not affected but the fertility was drastically reduced. In summary, acetamiprid, pyriprixyfen and cypermethrin showed a strong toxicity on H. axyridis eggs and embryos. Despite that some individuals from azadirachtin‐treated eggs successfully reached adulthood, their offspring was significantly lower than the control. More studies including other developmental stages of the predator would be needed to characterize the toxicology profile of these four insecticides for H. axyridis.