A review of control measures for blackberry downy mildew

Why the need for a review?

Recent losses of effective spray products, particularly close to harvest, have made it increasingly difficult for growers to gain control of downy mildew in blackberry. AHDB commissioned a desk study to review novel and alternative approaches, which might be relied on in future.

Key findings

All forms of protected cropping will reduce leaf wetness and minimise infection.
Before establishing a new crop, choose a site that avoids natural sources of infection, maximises light interception and maintains good air movement.
Reduce relative humidity in protected crops to below 85%. This can be achieved by reducing weed growth, maintaining adequate venting and where necessary, using air fans in glasshouse crops to improve air movement.
Manage nitrogen and other nutrition carefully to avoid excessive vegetative growth.
Photoselective polythene to alter the wavelength of light reaching the crop could affect the infection rate, but this requires further study.