The effect of UVB-blocking plastics on the efficacy of Beauveria bassiana and a conventional product against Lygus lineolaris on low tunnel strawberry.

Abstract

Effective, safe and practical biocontrol options are greatly needed for combating Lygus lineolaris on protected culture strawberry. This study demonstrated how ultaviolet (UV)-selective plastics can improve the efficacy of the fungal biocontrol agent Beauveria bassiana (Mycotrol) compared to the conventional insecticide acetamiprid (Assail) against L. lineolaris on low tunnel strawberry. We found that UVB-blocking treatments improved B. bassiana spore viability in both in vitro and in vivo laboratory experiments. In the field, survival of Mycotrol-treated sentinel L. lineolaris was lowest under UVB-blocking low tunnels, but this did not translate into significant differences among covering treatments in local L. lineolaris density or fruit damage. In contrast, applying the product Assail resulted in the lowest L. lineolaris density and highest quality yield compared to Mycotrol sprays. This was especially pronounced under low tunnels of any UV-limiting plastic. This study indicates that growing under low tunnels is a useful tool to improve the efficacy of conventional products and biopesticides containing microbial biocontrol agents. The efficacy of both products was improved under low tunnels, and specifically under UVB-blocking plastics for Mycotrol containing B. bassiana. However, there was little evidence that UVB plastics resulted in lower L. lineolaris densities and proportion of damaged fruit for either product in the field. Therefore we conclude that growing under any plastic covering is likely to benefit growers, but the economic value of growing under UVB tunnels is unclear. © 2022 Society of Chemical Industry.