Buckwheat strip crops increase parasitism of Apolygus lucorum in cotton

Cropping system diversification, including the in-field establishment of strip crops can improve the effectiveness of natural enemies and enhance biological control of pestiferous herbivores. In China, habitat management such as the in-field establishment of alfalfa strips is used for pest control in cotton. However, their effect on other economically important pests, such as the mirid bug Apolygus lucorum (Meyer-Dür), has not been evaluated. In this study, we first assessed parasitism of A. lucorum within plots of 13 different host plant species. Next, we established strips of one suitable plant species within a commercial cotton field and evaluated its effect on A. lucorum parasitism level. The results showed that two A. lucorum parasitoids, i.e., Peristenus spretus Chen et van Achterberg and Peristenus relictus Ruthe, responded differently to host plant species. In 2014, the parasitism levels of P. spretus were highest on buckwheat Fagopyrum esculentum Moench, while parasitism levels of P. relictus were generally low and did not differ between the various plants. Furthermore, A. lucorum attained low population levels on buckwheat. In 2016, A. lucorum parasitism levels in buckwheat plots were higher than in cotton. When (2 m wide) buckwheat strips were established in cotton fields, P. spretus parasitism of A. lucorum on cotton plants increased 2.4-fold in 2016 and 8.5-fold in 2017 compared to cotton monocrops. In conclusion, the establishment of buckwheat strips in commercial cotton fields enhances A. lucorum parasitism. By deploying these habitat management tactics, parasitoid-mediated biological control may complement existing management schemes for the polyphagous mirid bug in China and abroad.