Cedar Apple rust prevention

Asked March 13, 2018, 7:10 PM EDT

Hello- I have a young orchard with 20 trees of differing varieties. All of my honey crisp trees get CAR, likely due to the proximity of cedar trees in my area. Can you recommend A fungicide treatment and treatment schedule for the Annandale Minnesota area? I do take good care to remove all leaves from the previous season as well as other cultural considerations you mentioned in the other U of M publications.

Wright County Minnesota

1 Response

Thank you for the question. Planting disease resistant varieties and planting these varieties as far as possible from cedar and juniper trees/shrubs is key to controlling cedar apple rust. Pruning infected branches from your trees and removing the cedar apple rust galls in very early spring from nearby cedar and juniper also aid in control. Fungicides are often not required unless the tree loses vigor and drops leaves. If fungicides are used, they must be applied in the spring when flower buds first emerge.
The schedule of application depends on the directions given for the specific fungicide selected. In a review of several University of Minnesota publications, I found conflicting information so I checked with Michelle Grabowski, Extension Horticulture Specialist. Here is the summary of her answer which I think you find most helpful:

"Some of the confusion comes from the fact that some pesticides can be applied to ornamentals and not to plants we intend to harvest and eat from. Copper is typically not a good choice on apples because it can cause russetting of the fruit. Sulfur is an option but often provides limited control. Myclobutanil is your best choice. To use this you will need a fungicide that is labeled for use on apple trees. There may be multiple products of the same active ingredient, but if apple is not specifically listed you cannot use it on your trees. In the past I was unable to find a product for gardeners that allowed use on fruit trees but I looked again today and did find one product that does list apple on the label and would be an appropriate size for a home garden.

The application would need to be applied when the orange telial horns (gooey orange tentacles) are being produced on the cedar trees. This is typically early spring and the label states that application starting at pink bud (flower buds just emerging) will protect the tree from rust. Protecting the trees with the fungicide will only be necessary as long as the galls are producing spores. When the weather turns hot and dry for summer, the galls die and you can stop spraying. Keep an eye on your local eastern red cedars after a rain storm to know when the galls are done for the season.

As always read and follow all instructions on the pesticide label".

Thank you for contacting Extension.