Tailoring apple scab control strategies to the properties of the fungicides utilized

Description

Apple growers apply fungicide treatments every year to suppress apple scab caused by the fungus Venturia inaequalis. These treatments must be repeated depending on the infection risk, the appearance of new leaves since the previous treatment, and wash off due to rainfall. Treatments are generally carried out before a rainfall (protection). However, during periods of high growth or periods of prolonged rainfall, treatment strategies during (spore germination) and after (post-infection) rainfall may be needed to prevent high-risk infections. More than 20 different products to control scab, belonging to a dozen distinct categories, are registered in Canada. Choosing the right product to apply can be tricky because there is no chart comparing their actual performance for each application strategy. Furthermore, most labels do not clearly indicate the dosage required as a function of tree size or type of equipment used. To overcome these shortcomings, this project aims to develop a new scab control strategy based on selecting the lowest-risk products that best fit the circumstances at hand, and tailoring the doses accordingly. Together with a project already underway examining wash off, this project will provide growers with a complete picture of the available control tools, and a comprehensive comparison of fungicides with respect to their resistance to washout, their efficacy on growing leaves, and their effectiveness with regard to protection, germination, and post-infection. This project is also part of an applied research program on spraying that will enable growers to adjust the dose of a selected product, if necessary, according to their orchard type and the performance of their sprayer.

Objective(s)

• Characterize the fungicides used to control primary scab infections so growers can select the lowest-risk product that provides the best results for the circumstances at the time of treatment.
• Develop a comparison chart for 20 products, including the most popular products and low-risk products.