Ron Wilson

Ron Wilson

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Straighten Out Peach Leaf Curl - Eric Draper

As I was out and about in orchards seeing which apples have yet to picked and simply enjoying the colors of ripening fruit; suddenly, I was stopped in my wanderings to be absolutely stunned and amazed by the fall leaf colors of peaches. I had NEVER noticed the subtle colors and beauty of peach leaves that I observed for the first time this year. There were purples, reds, oranges, yellows and every shade or tint in-between and how beautiful they looked as they were starting to fall. I was savoring the moment, when my mind immediately jumped to- “Hey, peach leaves are falling… it’s almost time to control peach leaf curl!” I’ll be the first to admit that my mind doesn’t quite work along the same lines of thoughts as other people’s brains do!

Peach leaf curl (PLC), sometimes also called leaf curl, is a disease caused by the fungal pathogen, Taphrina deformans. Once seen, it is easy to recognize the unique symptoms of this fungus on peach foliage. However, PLC has the potential to also affect blossoms, fruit and young, green twigs, although these types of infections rarely occur here in Ohio. If ignored, this disease can have a major impact on fruiting peaches and nectarines, as well as ornamental flowering peaches. For backyard fruit growers, PLC is considered to be one of the most common disease scourges to manage in a home orchard.

Even if PLC may not be a problem every spring, it can be severe during cool, wet springs that follow mild winters! Now you know that there really is something good that happens due to our bitter, cold, winter weather! The seemly blistered, distorted, and reddish foliage that PLC causes, is easily seen in spring on the young, rapidly expanding leaves. These blistered areas become thicker and cause the leaf to pucker up, resulting in extreme distortion, creating its namesake “curl” as the leaf twists around upon itself.

The thickened areas first turn yellowish, then they may or may not redden in response to the fungal infection. As the fungus matures, the blisters and leaf will turn a fuzzy, grayish-white, as spores entirely cover the leaf blisters by the PLC fungus. After the spores are produced, infected leaves turn yellow or brown and drop off the tree. Depending on when the leaves drop off, the tree may produce new foliage.

Thank heavens, there is no secondary spread of this fungus! What that means is the spores from leaves infected in the spring, can’t infect any new leaves produced later in the season. Once infected leaves drop, no further symptoms will appear on any new foliage initiated during that growing season. However, leaf loss and the production of a second set of leaves, always has a cost to the tree! The typical results are a reduction in tree growth, meaning less bud wood for next season, while fruit size and overall numbers of edible fruits will plummet. Early leaf losses in the growing season, may also cause an overexposure of tender branches to sunlight, resulting in sunburn injury.

The fungal spores of PLC overwinter on the surface of bark and buds of the peach tree, creating multiple opportunities for leaf infections to occur very early in the growing season. During cool, wet spring weather, the overwintering spores germinate to initiate infections as the tiny leaves emerge from the swollen peach buds. Recommendations to effectively control the PLC fungus, require applying a single, VERY TIMELY, fungicide application. One may apply that fungicide in the fall after leaf drop or in the spring before buds begin to swell! Finding a window of dry weather for a fungicide application in the spring, coinciding with the timing for it to occur just as peach buds start to swell… is next to impossible!

In my humble fruit-oriented opinion, the absolute best time to effectively control this disease is right now! It is recommended to treat the trees just after most of leaves have fallen, usually late November or December. This is because you’ll want to treat every inch of the entire tree, bark, buds and all, with a fungicide. Leaves would just inhibit the ability to effectively treat and cover the entire tree, top to bottom.

The safest, effective fungicides available for backyard peach trees are copper soap (copper octanoate) or copper ammonium and are known as fixed copper fungicides. Apply either of these copper products with 1% horticultural oil to increase their fungicidal effectiveness. Bordeaux mixture also works but it is a home-made copper sulfate and lime mixture that must be carefully mixed just prior to treatment of the tree. The synthetic fungicides chlorothalonil, ziram, carbamates and ferbam are also very effective.

If PLC disease was a problem this past year, now is the time to do something to correct that issue. Get out there NOW and straighten the curls out of your future peach and nectarine leaves!

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