Issue 6, May 31, 2011

Peach Leaf Curl

Peach leaf curl seems to be prevalent this spring. Mike Roegge, Educator in Adams/Brown Unit has received several questions about this disease and I have confirmed an infection of peach leaf curl on a peach tree in Montgomery County. Reports of this disease are not surprising, as this pathogen favors cool, moist weather.

The causal fungi (Taphrina deformans) will over winter in buds and twigs, and if environmental conditions are favorable, will infect leaves and flowers anytime during bud swell to bud opening. It is possible that the recent, cool temperatures after budbreak, could have caused peach buds to take a longer time to open than usual, which allowed a larger window of opportunity for fungal infection.

Unfortunately, peach leaf curl is one of the most common and widespread disease of peaches or nectorines, but also can infect some ornamental Prunus species. Peach leaf curl can also occur, although rarely, on cherry and plum.

The good news is that this disease is not likely to kill the tree; however, leaf distortion and blister-like growths or puckering of the leaves are common. The leaves are often thickened and almost crisp; they turn downward and inward and may become red or purple. Infection can cause early leaf drop. Peach trees that show signs of leaf infection will have infection of fruit. Fruit growers are often concerned with reduced fruit quality due to this disease. If repeated infection to tree occurs, they can become weak, which may make them more susceptible to winter injury and other diseases.

Luckily, peach leaf curl is a monocyclic disease and secondary infection will not occur. The leaves will pucker and curl, spores will form on the leaves and fruit (peach fruit), and leaves will fall. Peach fruit will be shriveled and drop early. Then infected species will form new leaves that will not be infected.

If your tree is affected, it is too late for a fungicide application. If you are seeing this disease in your peaches, mark your calendar next year to spray lime-sulfur (Dormant Disease Control) before buds swell in the spring. Please note that if you apply lime-sulfur to green foliage, it may cause severe burn. After previously consulting, on several occasions, with Dr. Elizabeth Wahle, Extension Specialist, Horticulture, I have learned that she strongly encourages anyone growing peaches in Illinois to follow a spray schedule. If you would like to have a copy of the U of I recommended spray schedule for peaches (nectarines, apricots, plums, and cherries), it can be found on Table 5, on page 146 of the Home, Yard, and Garden Pest Guide.

If you happen to have an infected ornamental Prunus, you can apply calcium polysulfides, chlorothalonil, copper, or copper sulfate before buds start to swell next year. For additional information, you can refer to RPD 805 (Adobe PDF).

Growers and homeowners can help their trees by applying fertilizer now; however be careful not to over fertilize. This will help the tree produce new leaves and allow it to go into dormancy in late summer. (Stephanie Porter)

Stephanie Porter

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