Pests and Diseases: Cedar Apple Rust

Today’s post is about Cedar Apple Rust. It’s a quite interesting fungal disease that requires two plants to complete the cycle: the Eastern Red Cedar (Juniperus virginiana) and apple trees (crabapples too). Before we get started, let me show what the fruiting body on the cedar looks like…

cedar apple rust

Photo courtesy of fark.com

Isn’t that wild? It reminds of me of the drummer from the “Band” episode of Yo Gabba Gabba. Can you tell that I have a 3 year old?

cedar apple rust

The life cycle of Cedar Apple Rust goes like this:

  1. In the spring, the orange galls form on Eastern Red Cedars. As it rains, the spores are spread to nearby apples and crabapples (Malus spp.). When I say nearby, I mean within a 1/2 mile. As the rains subside in the spring, the galls dry up and no longer spread their spores.
  2. Once the spores land on an apple or crabapple, if the temperature and moisture level are correct, the spores grow and proliferate into orange pustules that are most often seen on the underside of the leaves.
  3. The spores grow there for the rest of the season and then are spread by wind back to the Eastern Red Cedar where they overwinter.
  4. When the temperatures warm the following spring, the cycle begins all over again.

 

Here is a picture of the infected leaves:

cedar apple rust

Photo courtesy of missouri.edu

If the fruit is infected, it can look like this:

cedar apple rust

Photo courtesy of umn.edu

So what can you do to prevent your apples and crabapples from being infected? Unfortunately, not a whole lot. Unless you live in the middle of a large acreage with a half mile around you that can be kept clear of Eastern Red Cedars, you stand a chance of infection. As the saying goes, the best defense is a good offense, so consider planting lots of different varieties of fruit trees. Don’t limit yourself to only apples and crabapples. Depending on what zone you are in, consider planting peaches, figs, paw paws and cherries. The chance that all of your fruit trees will be infected by some fungal disease in the same year are greatly reduced when you have a polyculture. If your apples succumb to Cedar Apple Rust one year, you’ll have other fruits to support you.

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March 27, 2012Permalink 1 Comment