Beyond Focal Pests: Impact of a Neonicotinoid Seed Treatment and Resistant Soybean Lines on a Non-Target Arthropod

Abstract

Integrated pest management (IPM) tactics may effectively control focal pests, but it is also important to test the compatibility of different tactics, and consider non-target organisms. We investigated the effects of a neonicotinoid seed treatment and Rag resistance genes used for soybean aphid (Aphis glycines Matsumura) control on reproduction of a non-target herbivore (twospotted spider mite, Tetranychus urticae Koch) in short-term greenhouse experiments. We also examined interactions between spider mites and a specialist phytoseiid mite [Ambylseius fallacis (Garman)] and assessed the effects of a co-occurring opportunistic omnivore [Frankliniella occidentalis (Pergande)] by including thrips density as a covariate. There were no interactive or main effects of the presence of Rag genes on the densities of any of the arthropods. Overall, effects of the seed treatment on spider mite densities varied, with no difference when mites were confined in clip cages, and higher populations on seed-treated plants when on whole plants. Predatory mites had a consistent negative impact on spider mites, and densities of A. fallacis immatures were similar between seed treated and non-seed treated plants. However, the relationship between spider mite and thrips densities was different between these two plant types, but only in the clip cage experiment lacking predatory mites. This research highlights the importance of considering how IPM tactics might affect non-target organisms.

Environmental Impacts of Arthropods as Biological Control Agents

“…Thus, when choosing biological agents for pest control, we need to know its effectiveness. There are various reasons for not using ineffective natural enemies, including the possibility of undesirable impacts on non-target organisms and on the ecosystem in which these organisms occur (Van Lenteren et al 2003, Özsisli & Prischmann-Voldseth 2016.…”

“…Besides, there should be an economic evaluation for the benefit of such an introduction, and studies need to be conducted on the impact of the exotic species in the natural environment. The potential risks of the release of exotic natural enemies have only recently received attention in biological control (Van Lenteren et al 2003, Özsisli & Prischmann-Voldseth 2016.…”

“…Until recently, tests with native non-target species had rarely been done as part of evaluation programs of natural enemies of arthropods (Van Lenteren & Woets 1988, Waage 1997, Barratt et al 1999, Wolfenbarger et al 2008, Romeis et al 2011, Biondi et al 2012, Özsisli & Prischmann-Voldseth 2016, Riedel et al 2016. However, the number of tests has been increasing, as researches are paying attention to its importance.…”

“…In the case of arthropods, there are proposals for the methodology of risk evaluation of biological control agents as a basis for the regulation of the introduction and inundative releases of exotic natural enemies. This evaluation integrates information on the diverse potential and characteristics of the species, for example, ability to disperse, range of possible hosts, and possible direct and indirect effects on non-target species (Van Lenteren et al 2003, Özsisli & Prischmann-Voldseth 2016. These studies of risk evaluation can indicate whether the species has high or low risk indices for its introduction.…”