Protecting Your Apple Fruit From Secondary Apple Scab

This 2020 growing season thus far is proving to be nearly as bad for apple scab as the 2019 season was.  We have received only 7.92" of rain since April 1, which is half the amount we received in 2019 for the same time period.  And, as of today, June 8, we have had  have had 8  apple scab infection periods as compared to 9 in 2019. But, with several of those infection periods lasting for more than 20 hours and one of them lasting more than 62 hours, which kept us from being able to get a cover spray on, resulting in over 3" of rain that washed off the previous spray, it has been pretty much impossible to control primary scab outbreaks.  With that being the case, we are at a point of now having to protect fruit from secondary scab.

Fig. 1

Season-long control is very difficult if primary infections develop, like those in Fig. 1, which produce secondary inoculum placing fruit at risk for secondary, conidial infections.   With primary ascospores possibly depleted, we will have to continue to monitor scab infection events and maintain spray coverage accordingly for at least two more weeks, if not longer, since we have found primary lesions,  like those in Fig. 2 on McIntosh and McIntosh hybrids like Cortland and Empire.  If you have seen lesions like those in Fig. 2, on your trees, then you will now need to protect your fruit from secondary lesions.

Fig. 2

The best product for protecting your fruit is Captan, a contact protectant. And that means that your trees will need to be sprayed with Captan at the full labelled rate prior to any rain event to protect your fruit.  If there are no rain events between sprays, a single contact protectant spray will last at least 10 days but not more than 14 days, based on the product's labeled information.  You will need to make sure that your trees and fruit are protected prior to any rain event  when using only a protectant. But, a protectant can lose its effectivness after 2" of rain, so you also want to reapply as soon as you can before the next rain event.   If no protection is available during the wetting event, then the liklihood of your fruit getting infected dramatically increases.

As always, be sure to follow the label directions on any spray product you may use.   For further information on control of apple scab, refer to:

 http://royaloakfarmorchard.blogspot.com/2018/04/apple-scab-season-approaches.html

Reference in this publication to any specific commercial product, process, or service, or the use of any trade, firm, or corporation name is for general informational purposes only and does not constitute an endorsement or certification of any kind by Royal Oak Farm.  People using spray products assume responsibility for their use in accordance with current label directions of the manufacturer for that product.