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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis
peach leaf curl
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Leaf Diseases of trees

Posted by John Fulton -

What a difference a year makes! Last year we were warm and dry for large parts of the spring, and this year has been cool and damp for the most part. With the type of weather we have experienced, it should have been expected many different diseases would come our way this spring. Well, they are here. Here are some shorts on the past week and some of the items found without looking too hard.

Peach leaf curl is caused by a fungus on trees in the stone fruit family. This would include mainly peaches and plums. It is rather striking with the bright red swellings on the green leaves. This disease can only be prevented with a dormant time application of a fungicide on your trees. Seeing it now means that you probably should have sprayed before the buds began to swell (meaning before leaves actually came out).

Anthracnose starts as dead leaf areas between leaf veins, or on the tips of leaves. When severe enough, leaves will fall. Several of the infected trees have actually had the leaves turn completely black already. It is much more noticeable on one side of many trees as well, due to air movement carrying the disease and drying out foliage quickly. The good news is that it rarely harms trees. If enough leaves drop, a new set comes out in 4-6 weeks and we start all over. The next set of leaves may also get the disease, but they may not. Infection can continue with weather favorable to the disease, and when nighttime temperatures stay under 65 degrees. Treatments when you see the symptoms of this disease are simply wasted time and money.

Apple scab is a disease similar to anthracnose, and can cause premature leaf drop in apples and crabapples. If you are on a regular spray schedule for fruit trees, it should prevent most of the problems. You could also spray crabapples this way, but you would have to weigh the cost and benefit since no fruit production is involved.

As a reminder, spray programs for disease prevention in fruit trees should be applied every 10-14 days after the bloom period is over. It should be stressed that these are preventative programs, and not curative. These programs then continue until roughly two weeks before the fruit is ready to harvest.

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