Integrated control of brown rot blossom blight by combining approved chemical control options with Aureobasidium pullulans in organic cherry production

In a 3-year study, the effectiveness of copper hydroxide, lime sulphur, and their combinations with Aureobasidium pullulans were investigated for blossom blight control in organic sour cherry production. The effect of treatments on phytotoxicity on spur-leaf clusters and yield was also determined. A major aim was to evaluate the integrated control approach of the combined A. pullulans treatments to reduce allowed chemical damage on spur-leaf clusters. Among fungicide treatments suitable for organic production, copper hydroxide and lime sulphur alone were most effective for blossom blight control when applied three times (at closed blossom, full bloom, and petal fall) during bloom. Both treatments were not as effective as the conventional standard, caused more damage on spur-leaf clusters, but significantly increased crop yield compared to the untreated control. A. pullulans treatments, applied three times during bloom (at closed blossom, full bloom, and petal fall), resulted in significantly higher blossom blight incidence but lower phytotoxicity compared to copper hydroxide or lime sulphur treatments applied alone. All A. pullulans treatments controlled blossom blight significantly better in all years and increased crop yield in two out of three years compared to the untreated plots. The need for an integrated approach to improve blossom blight management in organic sour cherry production is discussed. This is the first in-depth study on the multiyear effects of A. pullulans applications on blossom blight control in comparison with organically approved plant protection compounds of copper or lime sulphur for organic sour cherry production.