Possible Rust on Crabapple Tree?

Asked July 17, 2020, 1:25 PM EDT

We have had a healthy Royal Raindrops crabapple tree in our front yard for the last eleven years with no issues. Up through last year the foliage was dense and fluffy. This year, many of the leaves are half the size, the allover growth is much more sparse, and many of the leaves have reddish-yellow spots. We read that this might be rust, and that a nearby juniper or cedar could be responsible. Unfortunately, last year, a small juniper shrub was planted about 15' away around the corner of the house. We have checked it thoroughly for galls, but found nothing. Should we remove the juniper just in case? Hoping very much to save/revive the crabapple!

Wayne County Michigan

1 Response

Hello,
Thank you for sending such clear pictures! You are correct, the leaves of your crabapple indicate cedar- apple rust. Cedar-apple rust need plants from two plant families to complete their life cycle; the Cupressaceae family (eastern red cedar and other junipers) and Rosaceae (apple, crabapple, hawthorn, serviceberry). The juniper you recently planted seems to be the culprit since your crabapple just started having symptoms this year. Removal of the juniper will certainly disrupt the life cycle but be aware that the fungus can travel by wind within a ½-to 1-mile radius. So it is possible that if a neighbor has an eastern red cedar or junipers planted near you it will continue the life cycle. In most cases treatment is not used. There are fungicides available but timing is an issue and it must be done early in the spring, beginning as buds just start to break. Check around your neighborhood for any other juinpers or eastern red cedar trees. If you choose to remove the juniper, keep an eye on your crabapple tree for improvements next spring. Keep it watered, trees need at least an inch of water per week especially during the hot dry summer.

I am including the following articles that will provide more information.

https://www.mortonarb.org/trees-plants/tree-and-plant-advice/help-diseases/cedar-apple-rust

https://ag.umass.edu/landscape/fact-sheets/cedar-apple-rust

https://extension.umn.edu/plant-diseases/cedar-apple-rust#managing-rust-on-apples%2C-hawthorns%2C-and-other-plants-in-the-rosaceae-family-1172760

I hope this helps you out and contact AaE if you have any furthur questions.