Apivectoring of entomopathogen, Beauveria bassiana strain GHA for suppression of thrips on commercial greenhouse strawberries: a real life study

The cultivation of strawberries within greenhouse environments is an increasingly common area of agricultural productivity, affording consistent fruit production of an otherwise highly seasonal crop. However, due to its relative novelty, few management tools have been identified, assessed or registered to date for control of the many known pests of greenhouse grown strawberry crops. This includes evaluation of biocontrol strategies such as apivectoring, whereby microbial agents known to suppress crop pests are dispersed by commercially available pollinating bumblebees, Bombus impatiens (Cresson 1863) (Hymenoptera: Apidae). Towards addressing the need for such tools, this study evaluated the impacts of three periods of apivectoring in a commercial greenhouse strawberry production facility to determine how well the conidia of entomopathogen, Beauveria bassiana (Bals.-Criv. Vuill 1912), would be disseminated for control of crop pests such as the western flower thrips, Frankliniella occidentalis (Pergrande) (Thysanoptera: Thripidae). Our results indicate that bumblebees effectively dispersed a formulation of B. bassiana throughout the greenhouse crop, with the entomopathogen being detected on multiple flowers, leaves, and fruit. Furthermore, the impact of this tool on the quality of fruit produced, as well as possible adverse effects of the entomopathogen on carrier bumblebees were also evaluated. The B. bassiana formulation had minimal impacts on bumblebee populations, with under 16% mortality attributed to infection by B. bassiana . Through population monitoring, we found that naturally occurring thrips were being suppressed by the apivectoring biocontrol strategy, with up to 75% of Frankliniella occidentalis collected from some treatment zones testing positive for infection by B. bassiana.