Disease Control During the Dormant Season

Now that you have cleaned up the flower beds, tilled the vegetable garden and even raked a few leaves, you may be feeling a bit virtuous and think that you have done all you can in terms of disease control until next spring. However, for some diseases such as peach leaf curl, dormant season controls are extremely important in order to obtain good control.

The use of dormant season control measures is an especially important part of disease and insect management for fruit crops. If you were one of the many gardeners who were caught off-guard with peach leaf curl infections on peaches and cherries, you learned quickly that there wasn’t anything you could do about the problem once it occurred. Management of this disease relies on a single fungicide application made to a dormant tree anytime after leaf drop in the fall until bud break in the spring. Liquid lime sulfur (calcium polysulfide), Bordeaux mixture, copper-based fungicides (Kocide 101), chlorothalonil (Bravo 500) and ferbam (Fermate, Carbamate) are used to control this disease.

For the bacterial disease fireblight on apples and pears, inspect trees for overwintering cankers and remove and destroy them. A dormant season spray of Bordeaux mixture, or fixed copper will help delay production of inoculum in the cankers that were missed during scouting. Liquid lime sulfur applied in the spring before bud swell on grapes can help suppress levels of anthracnose, powdery mildew and Phomopsis cane and leaf spot. Delayed dormant spray applications of liquid lime sulfur to raspberry and blackberry canes just as green tips appear are useful in managing anthracnose infections. Dormant applications of superior oil are also important in managing scale infestations on many of these fruit crops.

Take some time during the next few weeks to assess the disease and insect problems you had on your plants last summer. If you have had problems in the past with these diseases or with scales, make a note on your calendar to apply these controls before the plants break dormancy. Be aware that if the weather is mild, dormancy may be broken earlier than in past seasons. The mild temperatures during last winter caused plants to break dormancy much sooner than in previous years; therefore, many gardeners missed the dormant season application. For more detail about disease and insect control on fruit crops through the season, you may find it helpful to consult MU Guidesheet G6010 "Fruit Spray Schedules for the Homeowner."

Laura Kabrick, Extension Plant Diagnostic Clinic