Insecticidal effect of halofenozide and methoxyfenozide in different stages of Lymantria dispar, an important cork oak defoliator

Abstract

The gypsy moth Lymantria dispar (Lepidoptera, Lymantriidae) is one of the most notorious pests of hardwood trees. It appears in cyclic way and provokes serious defoliations of the cork oak. In Algeria, L. dispar is reported since 1925 and the control of this defoliator consists of chemical insecticides and/or biological control tools. In this project we evaluated halofenozide and methoxyfenozide against larvae of L. dispar. These two molecules are member of a new generation of insect growth regulators that mimic the natural insect moulting hormones or ecdysteroids. Halofenozide is active against Lepidoptera and Coleoptera, while methoxyfenozide is more specific for Lepidoptera. We determined the toxicity and mode of action of these two insecticides by treatment of the larvae of L.dispar. In intoxicated larvae typical morphological aberrations during moulting/ metamorphosis were observed leading to death. In addition, we noted in the surviving adults a strong negative effect on the fecundity and fertility. The results are discussed in relation to the susceptibility of the different stages of L. dispar.

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