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Prevent Plant Diseases Now!

September 18, 2008

Many gardeners wait until a problem occurs; then scramble to correct the situation. This approach is generally costly, time-consuming, and does not produce a healthy plant. Consider instead, some lawn and garden cleanup procedures that help prepare plants for winter and discourage development of disease problems.

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

  2. Prune oak trees in the dormant season to reduce the risk of oak wilt. Pruning from September to early March is recommended because pruning during the growing season causes sap flow, attracting bark beetles, which in turn may transmit the oak wilt fungus.

  3. Prune trees and shrubs to remove all dead and seriously cankered wood, as well as any crossing and interfering branches. Opening up the center of woody plants helps promote faster drying, lets in more light, and reduces foliar and stem diseases. This is a common practice to help prevent fire blight on rosaceous hosts, anthracnose and fungal leaf spots of trees, bacterial leaf spot of Prunus species, as well as many other diseases.

  4. Provide winter protection for roses, evergreens, thin-barked young trees, and other sensitive plants. Winter injury causes wounds that become infected with secondary canker fungi. Many of the rose cane canker fungi infect such injuries.

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

  6. Remove and burn (where possible), compost, or bury plant debris to help reduce foliar and stem disease next year. It is usually safe to compost any leaf material; but diseased stem and root tissues should be burned or buried, not included in a compost pile.

  7. Look over a variety of seed and nursery catalogs. Select resistant varieties 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. If you have had problems with scab on crabapple, consider replacement with a scab-resistant variety showing flower and fruit color that you prefer as well. Try to obtain a variety that is also resistant to powdery mildew and rust.

  8. Make a map of your flower and vegetable gardens. Rotate annuals to another area of the garden to reduce soil-borne pathogens that cause Rhizoctonia and Fusarium root rots. Now is also a great time to make soil amendments to improve soil drainage. Phytophthora root rot is a known problem in poorly drained areas.

Of course these measures can not guarantee a lack of plant disease in your garden, but they can help reduce disease incidence.

Author: Nancy Pataky


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