Improved grey mould management on blueberries using the iLeaf-Botrytis-Blueberry-Model decision support system

Grey mould (Botrytis cinerea) on blueberries causes significant pre- and postharvest yield loss for commercial producers. Controlling grey mould is complicated by the crop’s overlapping blossom and fruit stages throughout the season. There is also a limited number of chemical control options registered for use once harvest begins. Decision support systems (DSS) or models for grey mould control on blueberry have been developed. A Chilean model was tested in South African conditions but rendered inaccurate results. A model-specific for South African conditions using hourly weather data was developed. The model was tested in 2020 in the Western Cape on two blueberry farms by comparing it to a standard calendar spray schedule and unsprayed control treatment in terms of the number of sprays scheduled per season and grey mould incidence on inflorescences of Eureka blueberry plants. The plants sprayed according to the iLeaf model needed similar or fewer sprays during the season than calendar sprays (9 vs. 6 sprays at farm A for calendar vs. DSS sprays, respectively, and 5 sprays at farm B for both treatments) and had similar or less Botrytis incidence on plants (1.25 vs. 1.26% incidence at farm A, and 1.53 vs. 1.19% incidence for calendar vs. DSS sprays at farm B, respectively). This study showed that spraying according to the DSS led to similar or better control of grey mould with a similar or lesser amount of fungicide applications per season.