The ornamental landscape is at its most beautiful when plants are healthy and growing well. Disease issues can reduce a plant's aesthetic value and impair growth, leading to dieback, leaf drop, or death.
Disease issues can be exacerbated by weather conditions. Even with prevention tactics, disease issues may still arise, especially when the weather favors their development.
Use these tactics in your landscape to reduce disease issues and improve the appearance of the many trees, shrubs, edible plants, perennials, and annuals.
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Disease Prevention Steps
- Scout often and address issues as soon as they are noticed. Most disease issues cannot be corrected, only prevented. By addressing the issue as soon as it is noticed, you can prevent it from spreading.
- Accurately identify the problem. You can only treat it appropriately if you know what the problem is.
- Not all things that look like a disease are caused by a microorganism like fungi or bacteria. Sometimes they are caused by environmental factors.
- Learn how to distinguish biotic and abiotic issues in this article: Biotic vs. Abiotic - Distinguishing Disease Problems
- Select varieties with disease resistance. Knowing common disease issues for the species you are growing allows you to select cultivars that are naturally resistant to those diseases.
- Promote vigorous growth by watering and fertilizing plants appropriately. This can help plants grow new disease-free leaves.
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Peonies grown in shady locations are more likely to develop powdery mildew (2) Provide ideal growing conditions. Plants growing in too much shade or poor soil are more likely to have disease issues.
- Avoid fluctuations in watering. Too much or too little water, as well as big swings in soil moisture, can make plants more susceptible to disease issues.
- Keep foliage dry. Most disease-causing microorganisms, like fungi, require water to proliferate. Dry foliage helps slow or prevent their growth.
- Avoid overhead watering. Soaker hoses, drip irrigation, or watering at the base of the plant all help keep the foliage dry.
- Don't work in the garden when the foliage is wet (from rain or heavy dew). You can accidentally spread diseases.
- Practice good sanitation. Clean tools and start seeds in clean containers.
- Eradicate weeds. Removing weeds can improve light penetration and air circulation and prevent them from serving as unintentional alternate hosts for diseases.
- Utilize mulch. Putting down a layer of mulch reduces soil splashing, which can spread disease-causing microorganisms.
- Plan to address issues if they have been observed in the past. If you've had issues with leaf spot on your dogwood the past two years, it's very likely to occur again. Be prepared.
- Remove and destroy diseased plant material. Especially at the end of the growing season after the first frost.
- Disease-causing microorganisms, such as spores, can sometimes overwinter on plant debris and reinfect plants the following year.
- Don't compost disease-infested materials.
- Use fungicides appropriately. Fungicides may be used to protect new plant tissue and prevent pathogen infection and spread.
- They rarely help eliminate the disease-causing agents (or their symptoms)
- Fungicide applications should always be used in combination with other management tactics.
- Remember to always read and follow pesticide labels.
More Information
- Managing Diseases in the Vegetable Garden
- Scouting for Landscape Plant Problems: An Integrated Pest Management Approach
- Proper Fungicide Use
- How to Prevent Turfgrass Diseases
Photo credits: 1: Aaron Steil; 2: Aaron Steil; 3: Iowa State University Plant and Insect Diagnostic Clinic; 4: Cindy Haynes; 5: Aaron Steil