June 14, 2008

Fungus Can Affect Peach Trees

By Staff Report

TROY -- This is a log of the questions called in or brought into the Horticulture Helpline run by the Miami County Master Gardeners. The help line operates from 10 a.m. to 2 p.m. Mondays through August.

Master Gardeners are available on these days to answer questions on the ground floor of the Courthouse in Troy.

To ask a question, call (937) 440-3945. Sandy Czajka, Jack Hepler, Alisha Miller, Elaine Richards, Doris Shaver, Ed Smith and Marian Moeckel will staff the HelpLine June 27.

Q A gardener brought in a leaf from a peach tree. Instead of the normal dark green color it was a bright spring green at the tip and pinkish near the base. The pink area was curled and deformed. This gardener has about 10 fruit trees but only one is showing signs of this problem. It is good to get it checked before other trees are affected.

A The problem is Peach Leaf Curl, Taphrina deformans. This is a fungus, which affects peaches and nectarines that occurs throughout North America during early spring when the weather is cool and wet. The curled areas will become reddish or purple and later may be covered with a gray or white coating of new spores (reproductive structures). With severe infections, blossoms, new shoots, and developing fruit may be affected.

This disease overwinters in the bud scales on trees, where it may remain dormant for many years. When conditions are right the spores will germinate and infect the buds early in the year, well before the first leaves appear. Once the infection develops spores are formed on the leaf surfaces and are spread by wind and rain to other branches and trees. These spores will cause infections the following spring. The length of the cool wet weather will determine how severe the infections will be.

To prevent the disease choose resistant or tolerant varieties of peaches and nectarines. If the leaves can be kept dry in late winter and very early spring, even susceptible trees may suffer little or not infection. Trees that are espaliered on the south side of buildings where the overhang may protect them or a temporary canopy of plastic during the infection period may work. Where possible, pick off infected leaves as soon as they appear and burn them, compost them (if it is a good hot compost), or dispose of them in the garbage to reduce next year's inoculum (spores).

Control the overwintering spores by applying dormant sprays of fixed copper, limesulfur, or Bordeaux mixture in fall, after leaves have dropped, and again in the early spring just before the buds begin to swell. Be sure to cover all plant parts thoroughly with the spray.

If leaf curl does result in significant defoliation in the spring, the fruit on affected trees should be thinned to compensate for the loss of leaves. Overcropping the tree will weaken it and make it more susceptible to winter injury.

Q My soft maple, silver maple, is shedding an unusual number of seeds. Is this unusual or does this occur every year?

A The seeds or double samaras (whirlybirds or helicopters) of the silver maple occur every year. Last year there may have been fewer seeds because we had the late freeze in April. Now that the seeds have fallen leaf production should improve as the season progresses. Many of the hard maples, sugar and black, for example, have not dropped their seeds yet.

Q Some of my bushes and plants are showing signs of shriveling and "corkscrewing."

We live across the road from a cornfield. The abnormal plant growth started about two weeks ago and occurs only in the front not in the backyard. We have never noted these symptoms in the 25 years we have lived here.

A It is difficult to say for sure, but it is possible that your plants are suffering from pesticide drift. It is possible that if or when chemicals were applied to the cornfield the wind was blowing in your direction. That would account for the problem in the front and not in the back. We recommend that you trim back the affected parts of the plants. Since it is early in the season, hopefully they will recover with only a brief setback.

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