By Trey Pitsenberger, co-owner
If you have roses, fruit trees, or other deciduous plants you should be thinking about applying a dormant spray to these plants starting around Thanksgiving. Powdery mildew, rust, scab and other diseases never go away completely in the fall and winter. They go hiding in the cracks and crevices of the bark and branches, lying dormant until spring, when the warm weather causes the diseases become active again. The same holds true with many insect pests. The insect become dormant in the recesses of the tree and shrub bark waiting until spring to reemerge and begin the cycle again.
To prevent problems in the spring apply a dormant spray starting at Thanksgiving. Dormant spray is usually a mixture of insecticide and fungicide mixed together and applied at the same time. The insecticide is usually a type of horticultural oil. This product coats the plant and smothers owerwintering insects. Since most insects breath through their skin the oil coats the bug causing it to die. The advantage of horticultural oil is it is very safe to use. People interested in organic gardening should know that organic gardeners extensively use these dormant sprays. This one type of spraying can reduce the amount of pesticide treatments needed during the growing season.
The fungicide portion of the dormant spray is usually either copper or sulphur. These two products have been around of years. Sulphur was used in ancient Greece on grape vines. These products kill on contact the organisms that cause such disease as scab, powdery mildew, rust, and black spot. Timing is important in your application of dormant spray. If it rains within twenty four to forty eight hours after spraying you will need to reapply it again. You should also apply dormant spray a few times during the winter. Three applications are best. The first application should be around Thanksgiving, the second at New Year, and the third around Lincoln’s birthday.
Dormant sprays like copper, sulphur, or horticultural oil have uses during the growing season as well as the dormant season. Be sure to read the instructions on the label before using dormant sprays. In the spring or summer the dilution rate for these sprays is much less than the dormant amount. If you spray in the summer with the dormant amount you could damage your plants. Spraying in the winter with the summer dilution just won’t do much good. Just make sure to read the instructions once before each use to familiarize your self with the proper dosage. If you have apricots be sure to use copper and oil while avoiding sulphur. Sulphur can be harmful to apricots.
Cleanliness is also important in the prevention of diseases and insects. Before spraying you should do any pruning that is necessary. This will mean you have to use less spray, as well as allowing the spray to penetrate into the branches. Be sure to clean up all the branches, leaves and fruit still hanging or fallen to the ground. Many diseases and insect hide in this debris and by cleaning up before spraying you will eliminate many of these pests.
Some of the plants that benefit from dormant spray are roses, fruit trees, fruiting vines, berries, crape myrtle, lilacs, deciduous magnolias, burning bush, Rose of Sharon, and almost any deciduous tree and shrub.