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Preventing the peach tree's nemesis.

If new leaves of peach or nectarine emerge puckered and brittle, chances are the tree has peach leaf curl. Once symptoms appear, it's too late to do anything about it this year. But you can prevent the disease for this season if you use the right spray just before leaf buds break open in winter or early spring.

Peach leaf curl is caused by a fungus (Taphrina deformans); rainwater-spread spores enter and infect leaf buds as the bud scales separate and expose the leaf tips. Leaves thicken, pucker, redden, then turn black and drop off in midsummer. In severe cases, the tree dies at this point. But most infected trees produce a second crop of healthy leaves from dormant buds, often at the expense of a fruit crop and tree vigor.

Spray with lime sulfur (calcium polysulfides) or fixed copper. Copper oleates are ineffective; they don't contain enough copper to kill all of the Taphrina fungus. Lime sulfur is faster acting and slightly more toxic than fixed copper, good for eradicating a bad case of leaf curl. You're more likely to have fixed copper in the garden shed since it's used against other diseases.

Remove any mummies (old, shriveled fruits) and prune the tree before spraying. A tank sprayer works best. Drench the entire tree--twigs, branches, and trunk--until the chemical drips. Any surface not hit by the spray, especially on twigs, might harbor fungus spores. Both copper and lime sulfur dry in half an hour; after that, rain will not impair the chemical's effect.

For control, you must spray every year. With proper annual spraying, you can even bring a tree infected for several years back to productivity. If you are planting a new tree, you should spray it this year as a precaution.
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Copyright 1984 Gale, Cengage Learning. All rights reserved.

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Date:Feb 1, 1984
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