Are Pesticides Used to Control Thrips Harmonious with Soil-Dwelling Predatory Mite Cosmolaelaps sabelis (Mesostigmata: Laelapidae)?

Abstract

Edaphic predatory mites could be introduced in pest management programs of pests that live, or spend part of their life cycle, in the soil. Some mesostigmatic mites have been widely used for the management of different species of thrips (Thysanoptera), especially in protected cultivation. The edaphic predator Cosmolaelaps sabelis (Mesostigmata: Laelapidae) was a model species in this study, being exposed to the most applied insecticides for the control of thrips in Brazil. After lethal, sublethal and transgenerational effects were evaluated. The pesticides acephate, acetamiprid + etofenprox, azadirachtin, spinetoram, formetanate hydrochloride, and imidacloprid were classified according to the IOBC/WPRS (International Organization for Biological Control-West Paleartic Regional Section) recommendation, considering the acute toxicity and the effects on adult females’ reproduction, in the maternal and first generation. The pesticides acetamiprid + etofenprox and azadirachtin were classified as slightly harmful (Class 2), while spinetoram was classified as moderately harmful (Class 3). Acephate and formetanate hydrochloride were classified as harmful (Class 4). Only imidacloprid didn’t cause negative effects on the females. Regarding effects on the first generation, acetamiprid + etofenprox, azadirachtin, and spinetoram caused reduction in the oviposition rates. Therefore, we suggest that complimentary bioassays should be done under semi-field and field conditions using the pesticides that were considered harmful in this study, to assess their effects on this predator in other environments prior to recommending not to use them in integrated programs to manage soil-based pests using chemical and biological tools.

Predator-Unfriendly Pesticides Harm the Beneficial Mite Neoseiulus idaeus Denmark & Muma (Acari: Phytoseiidae)

“…Silva et al [62] described a similar effect on two Brazilian populations of E. concordis. In addition to phytoseiid predators, acephate was also classified as harmful to Cosmolaelaps sabelisi (Laelapidae) [63]. Mixtures of neonicotinoids and pyrethroids may have a higher risk of toxicity to natural enemies because of the possible synergistic effect [64,65].…”

“…In contrast, the spinosyn-based insecticides can also be neurotoxic, acting by contact or ingestion [83], and harmful effects on natural enemies are more evident when they are ingested [84]. For example, higher mortality rates were observed in females of C. sabelisi (Laelapidae) when they ingested a mixture of Rabidtella axey (Nematoda) contaminated with spinosyn residues at a dose recommended for controlling thrips [63]. Driesche et al [85] found similar effects on Neoseiulus cucumeris (Oudemans) and Iphiseius degenerans (Berlese) (Phytoseiidae).…”