With wet weather about, growers should be prepared to act quickly to protect scars left on trees post-harvest, from infection.
Rob Saunders, Hutchinson’s Agronomist and Chair of the AHDB Tree Fruit Panel, provides his insight into managing Nectria canker disease risk in apples and pears.
Rob explains that trees are at most risk from infection during leaf fall, when thousands of scars leave entry points for spores to penetrate.
Canker infection is slow to develop, but once it is established, removal by pruning is the only way to eradicate it. Putting control measures in place now will be important to prevent shoot die back and fruit rot.
He says wet weather during leaf fall allows leaf scar infections to become established. Although autumn weather has been relatively kind so far, when it does rain heavily, the use of a protectant fungicide, such as Cuprokylt, is recommended.
Growers should remember that leaf scars are a difficult target and increasing water volume, with the addition of a wetting agent, is integral to achieving good protection.
Rob says another challenge is that leaf fall occurs over a period of time, and pruning is an ongoing job, but there are only a limited amount of chemical controls that can be applied.
The emergency derogation for Cuprokylt in apples and pears, for use at two key times of the season, will come as a welcome addition to the armoury, explains Selchuk Kurtev, Certis’ IPM Manager.
It comes at an important time for growers, as the EAMU is available now for treatment at leaf fall until 30 November 2018, and again between early February and 30 April 2019, or at the latest phenological stage bud burst, when trees are most susceptible to the disease.
Selchuk says appropriate application timings are crucial to manage disease risk. A maximum of 8kg/ha of Cuprokylt can be applied per year, split into four doses. He recommends two applications of 2kg/ha, two weeks apart at leaf fall, and two further applications at bud burst, unless growers have utilised previous derogations for scab control in the same orchard.