Dormant Copper Sprays and Sanitation for Disease Management
Kari A. Peter | 3/12/2019 | Penn State University
Below is an excerpt from Kari A. Peter at Penn State article on use of dormant applications of copper to manage fungal and bacterial diseases in apple, pears and peaches. Sanitation is critical for limiting fruit rots in the orchard.
Dormant sprays to manage fungal and bacterial diseases
Growers are encouraged to apply dormant copper sprays on apples and pears for fire blight and scab, and on peaches (and other stone fruit) for bacterial spot and peach leaf curl. Ziram and chlorothalonil (e.g., Bravo) are alternatives to copper and will also control peach leaf curl. Since peach leaf curl can only be managed when leaves are off the trees, applications should be made before bud swell. If using copper, growers will want to aim for 2 lb/A of metallic copper: pay attention to the % metallic copper equivalent (and amount of metallic copper per unit) listed on the label of the copper you use. Also, during dormant sprays, it is okay to mix oil and copper. Since minimal green tissue is present, the risk of phytotoxicity from the copper-oil mix is very low. Consequently, the emergence of green tissue will want to be monitored when this combination spray is used.
There is still time to get rid of overwintering scabby leaves
As a matter of principle, we began to monitor our overwintering leaves with apple scab for spore release last week, and no spores have been detected. This was expected since ascosopore release from infected leaves typically coincides with green tip. So far, green tip hasn’t occurred. Fingers crossed it won’t happen for another month… There is still time to keep apple scab in check if you haven’t done so already. Apple scab can be managed by reducing the number of available overwintering spores in last year’s leaves present in the orchard through sanitation. Remember: orchards are self-infecting when it comes to scab since spores can travel about 100 feet.