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Winterize to Help Control Plant Disease

October 27, 1999

Many gardeners wait until a problem occurs, then scramble to correct the situation. The next step usually involves asking for quick chemical cures (which usually do not exist). Consider and ask instead, “What can be done now to help prevent future disease problems in the lawn and garden?” Many disease problems are best controlled with preventive measures. Chemical rescue treatments may act as temporary Band-Aids but are usually not the answer for long-term disease control. These fall lawn and garden cleanup procedures help prepare plants for winter and discourage the development of disease problems.

1. Keep the grass mowed until it stops growing. This practice helps prevent damage from snow mold diseases and winter injury.

2. Prune oak trees now to decrease the risk of oak wilt. Prune from September to early March because pruning during the growing season attracts bark beetles that transmit the oak wilt fungus. Oak wilt is a potential threat in all of Illinois, but more so in the northern areas.

3. Prune trees and shrubs to remove all dead and seriously cankered wood, as well as any crossing and interfering branches. Open up the center of woody plants to help promote faster drying, let in more light, and reduce foliar and stem diseases such as apple scab, powdery mildew, and bacterial spots.

4. Provide suggested winter protection for roses, evergreens, young thin-barked trees, and other sensitive plants.

5. Prune tree and bush fruits according to the recommendations of Extension horticulturists.

6. Where possible, remove and burn, compost, or bury plant debris to help control foliar and stem disease next year. This is extremely important for canker diseases such as Cytospora canker or Botryosphaeria canker.

7. Look over a variety of seed and nursery catalogs. Select resistant varieties (if they are otherwise horticulturally acceptable) and plant them where you’ve had problems in the past but have no rotation options. Choosing disease-resistant hybrids, varieties, and species is usually the least expensive and best long-term method of disease control. There are bedding plants that don’t have to be covered with powdery mildew. Rust resistance is available in many bedding plants, vege-tables, and trees.

8. Make a map of your flower and vegetable gardens. Next year, move related plants to another area of the garden to keep down soilborne pathogens such as Fusarium, Rhizoctonia, and Pythium. This is a great time to make soil amendments to improve soil drainage.

9. Divide perennial flowers where it is appropriate, remove rotted or diseased parts, and replant in a new location.

Although we cannot guarantee complete disease control, these measures are sure to help attain a healthier garden.

Author: Nancy Pataky


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