[NAFEX] Cedar Apple Rust

Don Yellman don.yellman at webformation.com
Fri Jul 14 13:33:11 EDT 2006


I have been dealing with cedar apple rust for so many years I have lost count, in spite of removing the only eastern red cedar within eyeshot of the orchard.  There are enough others in the immediate neighborhood to keep the disease going, or perhaps my apple trees were generating their own infections.  I don't doubt that CAR can travel a half-mile from an infected tree, and maybe farther.  Persistent dormant spraying with lime/sulphur, then copper, had no effect.  Neither did any of the fungicides I had available at the time, including Mancozeb, Daconil 2787, Captan, and Benomyl, applied early in the growing season.  One season I made multiple sprays with a strong mix of cold-pressed neem oil, which had no apparent effect on either disease or insect problems.  But I learned that neem oil softens and destroys the rubber seals on my sprayer.  That took care of neem oil for me.

Cedar apple rust can progress well beyond the stage of leaf damage, and begin to affect a high percentage of the apples themselves, and that is where I was, particularly with susceptible varieties like Stayman, where nearly 100% of the little apples were infected.  CAR shows up on the small apples as a greasy yellow/orange substance that causes growth distortion and alters the apple flesh in such a way that the apples are unusable.  The most naturally resistant variety I had was Red Delicious, but disease resistant types like Freedom and Goldrush were affected as badly as the rest.

This past spring I made two applications of Ferbam, obtained from a neighbor who had a large stock of this fungicide purchased years ago that he had never used.  First application was made when the apples were in full bloom, the second about a week later.  Ferbam stopped the CAR cold, and there is not a single infected apple out there this summer among more than 30 varieties, many of them antiques like Calville Blanc, Ashmead's, and Cox's Orange, that are ordinarily highly susceptible.  There are still a few small spots on the leaves which I attribute to CAR, but very few and scattered.  Ferbam is a black substance that looks like ground up coal or asphalt, but mixes pretty well in water.  I had no mixing guidance, so used one level tablespoon per gallon, which seemed reasonable.  Using a 4-gallon backpack sprayer, two sprayerloads took care of the entire planting for each application.  No other fungicides have been used on the apples.

I would like to be as "organic" as the next guy, since I hate the work and expense of spraying, but theory seems to run head-on into reality.  There is no doubt about what I will be doing next spring at blossom time, and that is a couple applications of Ferbam.  I am not a professional, and there may be other fungicides or techniques to fight this disease of which I am unaware.  I know there are some that are "registered", which, for my purposes, means I can't get them.  But I think you can still buy Ferbam on the hobby grower market if you look around.

Don Yellman, Great Falls, VA

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