How to Treat Alternaria Leaf Blotch
- 1). Choose an appropriate fungicide and mix it according to the manufacturer's directions. Use a hand sprayer to distribute the fungicide. Wear a respirator, protective clothing and gloves to prevent contact with the fungicide. Choose a windless day to prevent the fungicide from drifting into surrounding areas. Use the spray in June for best effect, even though the added foliage makes it difficult to reach all areas of the tree. Spray three times at 10-day intervals starting in mid-June.
- 2). Control red European mite populations. Large mite populations will contribute to leaf browning, and also reduce the tree's ability to fend off the alternaria mali fungus. Check mite populations by collecting 25 to 100 spurs form around the orchard during the winter. If 10 percent of the twigs are infected, mites will become a problem when they hatch in the spring. Mite eggs can be identified with a magnifying glass. The eggs are red with a slim stalk and grooves on the bottom. If mites are present, spray with dormant oil before the apple trees bloom. Use protective clothing, gloves, eye protection and a respirator.
- 3). Chop off affected leaves with a mower throughout the orchard. The alternaria mali fungus lies dormant in leaves during the winter, so clearing fallen leaves from the orchard will prevent reinfestation the following year.
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