Cedar Trees + Apple Trees = A VERY Weird Disease
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Question. Is there any natural way to control cedar apple rust short of chopping down the trees? My junipers are full of the galls and my apple trees have developed the spots. The apples are in a nice breezy field, but, alas, surrounded by cedars. Help!
- ---Laura in Orange County, Virginia
Hello Mike! A friend in upper Bucks County, PA just emailed me these pictures of growths on his cedars. After a little Internet searching, I found pictures of cedar-apple rust disease that match. What does he need to do? Thank you,
- --Janet, also in Bucks County, PA
Answer. You forget how dramatic Nature can be until images like this remind you who the ultimate set decorator is! While the poor apple trees just get small yellowish spots on their leaves and disfigured fruits, the "gelatinous orange masses" that appear on cedars as their part of this weird symbiotic relationship are astoundingly large, astoundingly orange, and textured like giant morels. We'll post the pictures Janet sent along with this Question of the Week so you can see why the words "Alien life form" often appear in emails about affected cedars.
Here's how it all happens. The spores of a virtually unpronounceable disease (Gymnosporangium) land on an Eastern red cedar (or, less commonly, another member of the Juniper family), creating small greenish brown swellings on the very tips of the evergreen's needles. That's it for the first year. The following season, the swellings…well…swell…into hard brown dimpled, gall-like structures. Then the galls develop those highly distinctive bright orange 'hanging lantern' alien thingees, especially in a warm, damp Spring.
Those big orange goobers then release spores into the air that cause small yellow spots to appear on the leaves and fruits of any nearby apple trees. Those spots then produce their own spores; sticky ones that attract insects ("and what about apple trees DOESN'T attract insects?" I hear all the fruit growers out there screaming at their radios?).
Those insects then spread the spores all over the tree, often ruining the crop for that season. The fungus then colonizes the undersides of the apple tree's leaves, forms a new kind of fruiting body down there, and those spores blow back onto the needles of nearby cedars, thus setting up the cycle for the following year. You got all that? I'm exhausted just thinking about it.
My old Rodale Press "Pest & Disease Problem Solver" says: "You can prevent the problem if cedars and apples are separated by at least four miles", adding that, "this is sometimes difficult to accomplish." Gee? You think? Another source says you only need 300 yards; which doesn't sound that far until you start thinking football fields.
If I had a well-established orchard that these aliens were invading, I would probably bite the bullet and have any really nearby cedars taken down. Yes, it's sad to have to lose something as magnificent as an Eastern red cedar, but the aromatic, naturally rot resistant wood is among the best for building trellises, raised bed frames and such. Heck—if it was a really big specimen, I might try to sell some of the extremely valuable wood.
Conversely, if I had a big established cedar and wanted to start growing some apples (like I don't have enough trouble in my life already), I would plant naturally resistant varieties like "Empire", "Redfree", "Macfree", "Priscilla" and "Stayman".
And I'd try to keep ANY apple trees as healthy as possible. That means good pruning every winter to keep the trees open in the center; no chemical fertilizers; and no wood or rubber mulch. Clean the orchard floor every winter (which you should be doing anyway to prevent other problems) and mulch with an inch or two of compost early every Spring; this will feed the tree naturally and provide one less place for spores to breed.
Then I'd spray the trees with "Messenger" several times each season, especially in the early Spring. This protein-based organic disease-fighter supposedly acts like a vaccination to boost a plant's immune system. I've been using it for several years to defend my wife's peach trees, and so far so good.
Of course, apples also need to be protected against less dramatic diseases, and a great number of insect pests, so I would also spray the trees with a kaolin clay product like "Surround", which coats the leaves and fruit with a protective film. Keeping a clay cover on the trees in the Spring could well interrupt the cedar-apple cycle, as well as prevent other diseases (AND nasty buggies from eating your apples before you can).
And finally, prune out and remove as many of the disease's first year growths as you can on your cedars (or other junipers), especially those dimpled galls; they're where the disease spends most of its time. You may not be able to reach them all, but you might be able to bring them below critical mass.
Question. My mom's 5-acre lot is full of cedar trees. She loves them but they seem to be suffering from cedar apple rust (an orange growth that looks like a slimy ocean creature; Ugh!). The area is woodsy, and it doesn't matter to us if the cedars aren't "beautiful." We would just like them to survive. Thanks for any help!
- ---Concerned daughter Karen in Kintnersville, PA
Answer. You get the good news, Karen: The disease will not harm the cedars one bit. You won't be popular with any nearby apple growers, but your cedars will be fine. And if you get rid of any nearby apple trees (does she have a flowering crabapple maybe?), you might even be able to break the cycle completely.