Side Effects of Organic Products on Telenomus podisi (Hymenoptera: Platygastridae)

Abstract

Telenomus podisi Ashmead, 1893 is an important biocontrol agent, both in conventional and organic production systems. It can be used in association with other control strategies, such as natural botanical products and biological insecticides. Studies of selectivity and side effects are fundamental for proper management of insect control strategies because the interaction between different control strategies may negatively affect T. podisi. In this context, the present study evaluated the side effects of commercial natural products on T. podisi under laboratory conditions. Five natural products (insecticide, fungicide, and leaf fertilizer) allowed in organic farming were evaluated at concentrations recommended by the manufacturer in three bioassays. First bioassay (free-choice test), the preference of T. podisi parasitism between treated and non-treated E. heros eggs was assessed. In the second and third bioassay (no-choice tests) the treatments were applied to E. heros eggs, repectively before and after T. podisi parasitism (pre- and post-parasitism) and parasitism, emergence, offspring sex ratio, developmental time, and adult longevity were assessed. The products formulated with Metarhizium anisopliae (Metsch.) Sorok. (Hypocreales), Beauveria bassiana (Bals.) Vuill. (Hypocreales), orange oil fertilizer, and the fungicide copper oxychloride did not have side effects on T. podisi because they did not affect most of the evaluated characteristics. In contrast, azadirachtin A/B had a sublethal effect due to the reduced parasitism in all tests performed and, although it did not affect other aspects, this could compromise the performance of the parasitoid.

Selectivity of Metarhizium anisopliae and Beauveria bassiana to adults of Telenomus podisi (Hymenoptera: Scelionidae)

“…The longevity (L) and the egg-adult period (Po) were calculated using a weighted average as per Battisti et al (2020):…”

“…According to Potrich et al, (2009) parasitism is considered the main factor for the efficiency of parasitoids in the field. Battisti et al (2020) also observed that when the parental females of T. podisi are exposed to Metarril® and Boveril® products, applied on the host eggs, the percentage of parasitism and the percentage of offspring emergence are not affected. It is important to point out that these extreme conditions of contact will hardly occur in the field, as the parasitoid can fly and seek other environments and/or its host's eggs.…”

“…Parasitism was calculated considering the number of eggs per card (25) as 100%. The emergence percentage (Pe) and the sex ratio (R) were calculated by the following equations according to Battisti et al (2020):…”