Diseases That Infect Vegetables
Plant diseases—bacterial, viral, fungal—are rarely found in properly space and watered, well-fertilized home vegetable gardens. In this section, you’ll learn how to scout your vegetable plants for early signs of disease, match symptoms to specific infections, and find cures for the most common plant disease. You’ll discover:
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- The three types of vegetable plant diseases.
- Choosing disease-resistant vegetable seed and plant varieties.
- The importance of proper spacing, light, and airflow around vegetable plants.
- Care techniques that prevent vegetables from contracting diseases.
- Why disposal of diseased plant materials should be outside the garden, rather than in your compost bin.
Three Categories of Plant Diseases
Common diseases that infect your vegetable plants are nearly always either viral or fungal. A few bacterial infections also occur but are rarely seen in vegetables. Depending on the specific disease and infected plants, treatments and care may vary.
Most fungal diseases respond to prompt recognition and early treatment. Success in treating established viral infections, however, usually are beyond the capabilities of even professional horticulturists.
Fungal Plant Diseases
Even established fungus and mold infections are treatable. As is the case for for viral resistance, many fungus disease-resistant plant varieties are available for home plantings.
The most common fungal infections of vegetable plants are cucumber anthracnose, powdery mildew, scab, fusarium wilt, and verticillium wilt. Each has distinctive characteristics that will help you recognize the condition and can be treated using organic approaches [see Disease Symptoms, Causes & Cures].
Another condition caused by fungal disease that you may encounter early in spring is damping-off. Actually, several different fungi can infect newly sprouted starchy seeds planted in moist, cool soil. All cause similar symptoms: The stem of the seedling develops a telltale brown score at the soil line, then rots completely through.
Avoid damping off by planting large-seeded species when the soil temperature has reached at least 60°F (16°C).
Incurable Viral Plant Diseases
The most frequently seen viral diseases—despite nearly all susceptible vegetables having readily available resistant varieties available for planting—include cabbage yellows and tobacco mosaic viruses.
Yellows infects, weakens, and can kill broccoli, brussels sprouts, cabbage, cauliflower, and kale, while mosaic generally stunts and kills tomatoes and its relatives.
Your best bet for thwarting viral diseases is to choose plants resistant to the most common viral strains found in your region and rotate your plantings to new locations in your garden each year. Allow several years to pass before planting them in the same location again.
If your vegetables should contract a viral disease, it is important to prevent the infection’s spread.
Uproot and burn—or otherwise dispose of plant matter outside of the garden—all infected plants once you recognize the disease condition. Do not compost diseased foliage, and avoid planting the related species in beds that experienced infection during prior seasons.
Disease Prevention
Proper spacing, ample air circulation, and good watering practices will prevent most fungal diseases. All fungal diseases stem from spores found naturally in the soil or carried by the wind.
To germinate, the spores must find a dark, moist environment with plant tissue for food. Keeping foliage dry is of the essence for fungal-disease prevention.
Always water your vegetables at the soil line and avoid splashing or spraying their foliage unless you irrigate early in the morning of a warm, dry day when the sun and wind quickly will dry your plants’ leaves. Using these care techniques will prevent both downy and powdery mildew.
You can reduce further the hazard of communicable plant diseases from your garden by avoiding large, single-species plantings. Promptly remove all fallen, decayed leaves and plant matter from around your vegetables.
Gardeners who use tobacco products should be aware that tobacco mosaic virus inadvertently may be spread to susceptible garden vegetable plants by contact with cigarettes, cigars, or chewing tobacco. Always wash your hands thoroughly after smoking when handling tomato plants, or wear rubber gloves while touching, pruning, or harvesting.
By inspecting your plants frequently and taking these simple precautions, your garden will be a healthy place filled with thriving vegetation filled with fruit and leafy greens.