Using model-based fungicide programing to effectively control Botrytis and Anthracnose fruit rots in Mid-Atlantic strawberry fields and co-manage strawberry sap beetle (Stelidota geminate)

Abstract

Effective fruit rot management is essential for profitable strawberry production in the Mid-Atlantic. With recent fungicide resistance development in two high-impact fruit rot pathogens, Botrytis cinerea [the cause of Botrytis fruit rot (BFR)] and Colletotrichum acutatum [the cause of Anthracnose fruit rot (AFR)], there is increasing interest in using disease forecasting to reduce fungicide applications and thus preserve existing chemistries. We conducted field trials in the Mid-Atlantic over two years to evaluate use of a model-based fungicide program [the Strawberry Advisory System (StAS)] for: (1) efficacy in reducing fungicide applications, (2) ability to achieve fruit rot control similar to the existing calendar-based program, and (3) effects on non-target diseases and pests. Across the two years, fungicide applications were reduced by an average of 50% for BFR control and 58% for AFR control. The model and calendar-based programs resulted in similar yields in both years, based on both percent of marketable fruit and marketable fruit yields (P > 0.05). Confirming fungicide treatment efficacy, yields were significantly lower in the non-treated control (NTC) in 2016 (incidence: P = 0.024; fruit biomass: P = 0.012). Yields were uniform in 2017, with 94–96% of fruit marketable, and there was no treatment effect. AFR incidence in the calendar and model-based programs were similar in both years (P > 0.05). AFR incidence in the NTC was significantly greater than both fungicide treatments in 2016 (P = 0.004) but not in 2017 (P = 0.63), likely due to low AFR levels (<2% of fruit with AFR across treatments). BFR incidence in the model-based program was likewise similar in model and calendar programs in both year (P > 0.05). Neither program differed from the NTC in 2016 (P = 0.84), likely due to low BFR levels (>4% of fruit with BFR); in 2017 BFR incidence in the NTC was significantly greater than calendar program (P = 0.032). This study also revealed a 55% reduction strawberry sap beetle (Stelidota geminate) incidence in the model-based fungicide program compared to the NTC (P = 0.027) in 2016 due to reduction in fruit rots. Model-based spray programming therefore has the potential to mitigate fungicide resistance development in the Mid-Atlantic strawberry production while providing effective fruit rot control. Potential to co-manage strawberry sap beetle should be further examined and would greatly enhance industry profitability.