Effectiveness of fungicide treatments following the Strawberry Advisory System for control of Botrytis fruit rot in Florida

Florida strawberry production is highly affected by plant diseases. Botrytis fruit rot (BFR) is an important disease that can cause more than 50% yield losses if not well-managed. The disease is traditionally managed in Florida by preventative fungicide applications using a multi-site fungicide in early season when environmental conditions are less conducive for disease development and single-site fungicides during bloom when the environment is more conducive. More recently, many Florida growers have been following the Strawberry Advisory System (StAS), a web-based disease forecast system, to improve timing and reduce the number of fungicide applications. In this study, we evaluated the effectiveness of different fungicides used after StAS spray alerts compared to Calendar-based applications with the objective of implementing specific fungicide recommendations for Botrytis control into StAS. Two field trials were conducted, one in 2013-2014, and the second in 2014-2015 season. During periods that predicted high risk of disease incidence, BFR was best managed by StAS-triggered applications of fludioxonil + cyprodinil, or fluopyram. Yields were increased by StAS-triggered treatments that included fludioxonil + cyprodinil, thiram and the SDHI fungicides fluopyram, penthiopyrad, and fluxapyroxad, and the Calendar-based treatment in one season. However, the StAS-triggered treatments had about half the number of applications of the Calendar-based program. Our results show that timing and the choice of the fungicide to be sprayed when weather conditions are highly favorable for disease development are key to effective management of BFR.