Unfortunately, April showers sometimes means we should look for more than just May flowers. The current cold, wet weather pattern likely means home orchardists will be taking extra precautions to project apples this year.
“With the recent continuing rains and the projections for even more rain, the chance of foliar disease is extremely high,” said Richard Hentschel, Horticulture Educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. “In addition, the window of time to take action may be small between rains.”
Two common foliar diseases, Cedar Apple Rust and Apple Scab, can infect both leaves and developing apple fruits. Both are early springtime diseases that favor cool, wet weather. The infection starts as the buds swell, and as leaves and flower buds appear, said Hentschel.
Cedar Apple Rust is a two-host rust needing an evergreen host to overwinter before infecting apple trees and most of our ornamental flowering crabapples. Cedars and select ornamental junipers serve as common hosts for the rust, but are not greatly impacted by it. Apple Scab overwinters on last year’s leaf litter and does not require another host.
“Cedar Apple Rust and Apple Scab may begin each year in different ways, but they both spread with wind and are favored by the same weather,” he said. “Because of this, the source of infection can be anywhere in the neighborhood, and the best management practice is to protect the apple or crabapple tree.”
As long as it remains cool and wet, the infection period will continue, Hentschel added. Only when we have warm dry weather will the infection period slow and eventually stop. In addition, if you wait until disease symptoms are visible on leaves or fruit, it is too late to treat.
Nearly all retail garden centers and nurseries carry appropriate treatment options, often listed as “home orchard” or “fruit tree” sprays. They most likely contain one or more modes of action for disease control, as well as insect control.
“Any sprays applied must thoroughly cover all new and expanding leaves to provide adequate control of both Cedar Apple Rust and Apple Scab,” said Hentschel. “As always, read and follow label instructions carefully for safe, effective treatment.”
In addition to spray treatment, if you have apples or crabapples and cedars or junipers on your property, you could scout for Cedar Apple Rust galls and remove them. Look for small gray, brain-like structures in the branches, or soon, look for a bundle of orange fingerlike structures that release the spores.
“Remember, removing the galls in either form from your own yard will not protect against the disease completely, as it is spread by the wind, but it may help limit the amount of spores near you. It is still recommended to treat apples due to the increased threat of both diseases in our current conditions.”
For more information on growing apples, visit extension.illinois.edu/apples/growing.cfm