We are going to be putting in a "mini orchard" of about 15 apple trees fairly soon and just heard of something called cedar blight or cedar apple disease. Does anyone know what causes this and any remedies? We have cedar trees on the property and are wondering if they could hurt the apple trees.

-- Laurie (SUPERGS63@AOL.COM), March 29, 2000

Answers

It is called cedar rust, or often cedar apple rust. The red-cedar and the apple are alternate hosts for the so-called rust. The rust causes light-yellow spots that change to orange on the leaves and fruits of apple trees in spring and summmer, and produce galls on the cedars during the winter. These galls are quite gross and release an orange ooze in in the early spring which is in essence, spores that then go back to the apple trees to produce damage there. Sprays will do a pretty good job of protecting the apple trees from damage if you care to use them.

-- greenbeanman (greenbeanman@ourtownusa.net), March 29, 2000.

You can buy apple trees that are supposed to be resistant to cedar apple rust which is what I did. I got mine from Stark Bros. I bought Johnafree and Goldrush but I believe there is also a Freedom and Liberty that are supposed to be resistant to the rust. I don't like to spray if I don't have to

-- barbara (barbaraj@mis.net), March 29, 2000.

Cedar-Apple Rust

Problem Pale yellow spots appear on the upper surfaces of leaves and on fruit in mid- to late spring. These spots gradually enlarge, turn orange, and develop minute black dots. Small (1/6 inch) cups with fringed edges form on the lower surfaces of the leaves. Infected leaves and fruit may drop prematurely; the fruit is often small and deformed.

Analysis This plant disease is caused by a fungus (Gymnosporangium juniperi- virginianae) that affects both apples and certain species of juniper and red cedar. This fungus cannot spread from apple to apple, or juniper to juniper, but must alternate between the two. In the spring, spores from brown and orange galls on juniper or cedar are blown up to 3 miles to apple trees. During mild, wet weather, the spores germinate and infect the leaves and fruit, causing spotting, and eventually premature leaf and apple drop. During the summer, spores are produced in the small cups on the underside of the leaves. These spores are blown back to junipers and cedars, causing new infections and starting the cycle over again. For more information about cedar-apple rust on junipers, see Cedar-Apple Rust.

Solution Cedar-apple rust cannot be controlled on this season's apples and leaves. Next spring, spray apple trees with a fungicide when the flower buds turn pink, again when 75 percent of the petals have fallen from the blossoms, and once more 10 days later. When practical, do not plant apples within several hundred yards of junipers or red cedar.

-- Grant Eversoll (thegrange@earthlink.net), March 29, 2000.

Control Many methods can be used to control or prevent rust infection. Spray infected plants with a fungicide containing triforine, chlorothalonil, mancozeb, maneb, or zineb. Make sure your plant is listed on the product label. Pick off and destroy badly infected leaves as long as the practice doesn't damage the overall beauty of the plant. Keep the foliage as dry as possible. One way to do this is to water in the morning, which gives the plant a chance to dry out quickly, reducing the chance of infection. The best way to avoid rust infection is to plant resistant varieties of grasses, flowers, vegetables, and woody ornamentals, which may be found in local nurseries or through seed companies.

-- Grant Eversoll (thegrange@earthlink.net), March 29, 2000.

Laurie All of the info posted so far is very good to the best of my knowledge. A couple tangents I will take as follows: If it is at all practical removal of the cedars is probably a far simpler solution to spraying , chemicals are chemicals enough said, their effectiveness however is dependant on numerous variables, percent coverage, weather, health of plant, etc., making them a rather laborious and often partial solution at best. I have had some pollination problems with the "hybridized" or shall I say "specialized" apple trees we purchased for specific reasons here in Western New York. So by all means , if you choose this route, Know your plants and your supplier well and ask specific questions in regards to your climate, drainage, orchard plans etc. and never purchase a plant that isn't guaranteed for at least one full year from purchase, ,,,,, Good Luck and I hope there are many pies in your future.

-- Daniel Baker (dcbaker@2ki.net), March 31, 2000.

Q: What about the Cedar tree's themselves? Isn't there something that can be put on them instead of putting the burden my neighbor that owns the Apple tree's?

-- Joseph Reese (quackerbox@webtv.net), March 15, 2002.