Time to Spray for Peach Leaf Curl
Anyone who grows peaches in the upper Midwest should be warned that NOW is the time to spray for peach leaf curl control. This disease is caused by a fungus (Taphrina deformans). The fungus overwinters on peach trees bark and buds. Once the bud scale swells and crack in the spring prior to leaf out, the fungus gets into the meristem and is impossible to control. Developing leaves will be puckered /twisted with red or yellow coloration to the infected area.
All new growth will show distorted leaves for months. While this disease is primarily a foliar issue, it can indirectly cause the fruit to be smaller and even weaken the tree if the number of infected leaves is severe.
The only time to control this disease is to apply a preventative fungicide to the entire tree (branches, trunk etc.) while the tree is still dormant in late fall or early spring. Here in SE WI, I find it difficult to spray my peach trees in late fall as they tend to hold their leaves until the second week in November. By that time I have my exterior water line turned off and everything winterized. Instead I find it easier to apply two applications of a fungicide in Spring. Weather permitting, I try to spray once in mid-late March and then a second application the first week in April. Usually by April 5th-10th my peach buds have swelled and the bud scales have cracked. It is useless to spray after the bud scales are cracked/opened as the fungus usually has already penetrated into the meristem and no amount of spray will control it.
Some years I only get one application applied due to weather issues but I try for two to be safe. The type of fungicide to use is very important. Fungicides containing chlorothalonil usually work well on controlling this disease. To find the proper fungicide we unfortunately have to play the pesticide name game. I must explain as all pesticides have three different names (chemical, common and trade name).
The chemical name is only useful for chemists. The two names important for most of us are the common and trade name. Every pesticide had a common name for any active ingredient in it. Various manufacturers can make a pesticide with that same ingredient but can sell it under their trade name. An example is Sevin insecticide. Sevin is the trade name. The common name for the active ingredient is carbaryl.
In the case of peach leaf curl, I recently went out to purchase some fresh fungicide to use on my peach trees. At the store, I found three different products which all were made up of the same active ingredient (chlorothalonil at 29.6%). One product was called Bonide Fungonil. The other two were Ortho products called Ortho Garden Disease Control & Ortho Disease B Gone ™.
Since all 3 products contain the same active ingredient at the same strength (29.6%) all three should do the job. All three were in 16 oz. containers. The big difference was price. Two of these products were $20 and the third was $17. Of course I chose the least expensive. Yes it pays to read the ingredient labels on pesticides before purchasing. In this case for controlling peach leaf curl, I can only advise to use any product containing chlorothalonil as it has worked well for me in the past. Since fungicides are often sold
by confusing trade names, the common name is best to find out if the product will work for you.
You should also always check if the pesticide label on the product shows that it is registered for use on the crop you are growing and follow all safety and application instructions listed.
Paul Schwabe is a salesman in our Contractor Sales division. He holds a degree in horticulture and will be writing about some of his favorite and underused plants.