Management of flowering plants to promote functional agrobiodiversity in strawberry whilst minimising damage caused by Lygus spp.

Abstract: Sowing flowering plants provides an alternative food source (pollen, nectar, and
alternative prey) which attracts and increases beneficial arthropod populations in (soft) fruit
crops. It is a promising tactic for enhancing the biological control of key pests like aphids and
thrips in strawberry. However, polyphagous Lygus spp. populations (Hemiptera: Miridae) can increase as well, resulting in higher numbers of deformed strawberry fruits, also referred to as ‘cat-facing’ fruit). In this study, plots of flowering plants sown next to flowering everbearers (cv. Verity) underwent different management strategies to suppress Lygus spp. populations, in particularly the European tarnished plant bug Lygus rugulipennis (Poppius). The different management options included strategic mowing of the flowering plants, either twice (just before egg hatch of the first and second generation harmful bugs) or only once (before egg hatch of the second generation). Timing of mowing was determined by a temperature based phenological prediction model for L. rugulipennis. In addition, treatments using both entomopathogenic fungus (Botanigard®, ai Beauveria bassiana GHA strain) and synthetic insecticide (Decis®, ai deltamethrin) were tested. The timing of both products was also based on predicted Lygus spp. phenology, with either one application targeting adults of the second generation, or two applications targeting adults in both the second generation adults as well as the active overwintering adults for the synthetic and biological treatments, respectively. Finally, the effect of hexyl butyrate dispensers on repelling L. rugulipennis bugs was also evaluated. All tested management options showed a trend towards reduced Lygus bug deformed fruits. Two strategic mowings (before egg hatching G1/G2) as well as the repellent hexyl butyrate dispensers resulted in similar reductions (~ 50 %) in bug damage as the synthetic deltamethrin reference treatment.