Golden Delicious Spots

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cireson
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Joined: Sat Aug 13, 2011 9:37 am
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city_state: Portland_Maine

Golden Delicious Spots

Post by cireson » Sat Aug 13, 2011 9:48 am

What is this fungus and how can I eliminate it in the future. The tree has these scabs on many of the leaves and spots on most of the apples. The golden delicious tree is also dropping leaves and numerous apples.
Image
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Appledoc
Posts: 51
Joined: Mon Nov 17, 2008 10:16 am
Location: Winchester, VA

Re: Golden Delicious Spots

Post by Appledoc » Mon Aug 22, 2011 5:49 pm

The prominent orange lesions in the top picture are one of the apple rust diseases, probably cedar-apple rust, which requires the alternate host eastern red cedar to complete its disease cycle. The most effective product for apple rust control available to home gardeners is Spectracide Immunox Multi-purpose Fungicide. I suggest applying it at early pink stage (before blossoms open), at petal fall, and again 10-14 days later. The rust gall spore supply on the cedar tree should be depleted by about three weeks after petal fall and there is no secondary rust infection cycle in the apple tree. The small tufts projecting from the underside of an orange lesion at the top center of the top picture are the "aecia" where the spores are produced that go back to re-infect the cedar tree in late summer and fall.

The whitish area near the bottom center of the top picture could be powdery mildew which is also suppressed by Immunox but it might need two more applications after the petal fall spray.

The less dramatic, olive brown lesions on the fruit and leaf at the bottom of the bottom picture, are apple scab. It is controlled by a general purpose "home fruit spray", starting before the first wetting period at the earliest green-tip stage and repeating every 7-10 days, but to protect the bees and other pollinating insects, avoid spraying a product that contains an insecticide during bloom. You can mix Immunox with a "home fruit spray" product to ensure better control of the rusts and powdery mildew. (The typical fungicide in home fruit spray products is captan which is not effective on rusts and mildew).

The rather large, tan-light brown spot just to the left of center in the bottom picture is tentiform leaf miner injury. This is caused by the larva of a small moth feeding inside the leaf. It has a rather high action threshold, even in commercial plantings, and probably shouldn't be much of a concern in the home fruit planting unless there are several mines per leaf.

The leaves might be dropping because of heavy rust or scab infection or due to physiological stress (called Golden Delicious leaf blotch); a lot of premature fruit drop could be due to codling moth infestation but that isn't evident in your pictures.

Use all pesticides according to their labels.
Good luck next year!

Appledoc

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