Abstract
This study investigated the direct effect of the insecticides deltamethrin and spinosad on three egg parasitoids species: Trichogramma oleae, T. cacoeciae and T. bourarachae. The parasitoid pupae were exposed to pesticide residues on fresh olive tree leaves at recommended concentrations (RC) at different time intervals: 3, 10, 17, 24 and 31 days after pesticide applications. Parasitism viability (% emergence from parasitized eggs) and adult emergence time (developmental time from pupa to adult emergence) were evaluated. Regarding to the International Organization of Biological Control (IOBC) guidelines, results of toxicity effects of insecticides show that: Deltamethrin was moderately harmful to all Trichogramma species at RC (Decis® 100 milliliters·ha−1), however, spinosad was harmless to moderately harmful at RC (Tracer® 20 milliliters·ha−1). Trichogramma species revealed differences with regard to adult emergence time and exhibited significant changes in parasitism viability with increasing time after pesticide treatment. While deltamethrin residues affected parasitism viability 31 days after the product application, spinosad displayed similar viability for almost species 24 days after the application. The usefulness of Trichogramma parasitoids used as biological control agents, in olive tree ecosystem, was discussed in integrated pest management programs for Prays oleae control when parasitoid species were exposed during pupal stage to the insecticide residue.
Highlights
Integrated Pest Management (IPM) is an effective and environmentally approach to pest management that relies on a combination of chemical and biological control methods
The effect of the insecticides was established by comparing the controls with the treatments using the following formula: E (%) = (1−Vt / Vc)×100 where E is the insecticide effect in parasitism viability compared to the control; Vt is parasitism viability observed for each insecticide treatment and Vc is the parasitism viability observed in the control ones
The present study was designed to evaluate three Trichogramma species: T. oleae, T. cacoeciae and T. bourarachae for their susceptibility to deltamethrin and spinosad when exposed at pupal stage of development
Summary
Integrated Pest Management (IPM) is an effective and environmentally approach to pest management that relies on a combination of chemical and biological control methods. Contact with pesticides at the less susceptible life stage (parasitoids within hosts) can cause prolonged development time of immature stages and reduced emergence from parasitized eggs [9]. This is important to determine the compatibility of parasitoids with pesticides for IPM programs. The present study was designed to determine the side-effects of two insecticides deltamethrin (Decis®) and spinosad (Tracer 240®) on three native Trichogramma species T. oleae, T. cacoeciae and T. bourarachae [24] and to discuss their possible use in control programs against the second generation of P. oleae in olive grove areas where biological control has limited use
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