Potential use of biofungicides and conventional fungicide for the management of Botrytis blossom blight in lowbush blueberries

Abstract

Botrytis blight is an economically important disease of lowbush blueberry that causes significant yield loss annually. In this study, the biofungicides, Diplomat 5SC&#174; (polyoxin D), Timorex Gold&#174; (tea tree oil), Fracture&#174; (BLAD) and Serenade MAX&#174; (<i>Bacillus subtilis</i>) were evaluated for their disease suppression potential against <i>B. cinerea</i> individually and in rotation with Switch&#174; (cyprodinil and fludioxonil) under field conditions. Three applications of each biofungicide were made for the stand-alone treatments at 7–10 day intervals, with Switch&#174; replacing the biofungicides during the second applications in the combined treatment. Results indicated that the products have the potential for use as a biofungicide in lowbush blueberries. All the stand-alone and rotational applications brought about a significant reduction in disease development, especially in 2019. The application of Diplomat 5SC&#174; and Fracture&#174;-Switch&#174; rotation decreased disease development by over 63% in 2018. In 2019, all stand-alone treatments reduced disease development by more than 42%, whereas their rotation with Switch&#174; reduced disease by over 69% at one site and at least 30% at another site. Stand-alone Diplomat 5SC&#174; and Timorex Gold&#174; along with Fracture&#174;, Timorex Gold&#174; and Serenade MAX&#174; rotation resulted in over 20% more berries. This study suggests that the biofungicides and their integration with chemical fungicides have the potential as an alternative management strategy against Botrytis blossom blight to reduce the use of conventional fungicides and produce fruit with no detectable fungicide residues.