The most common diseases to infect vegetable plants are either viral or fungal in nature. (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.
A common plant disease that might infect your vegetables is powdery mildew.
Photo Credit: ©2002 Dolezal Publishing/Donna Krischan
Brown, withered stems and toppled young plants from newly sprouted seed are due to a fungal disease caused by damping-off.
Photo Credit: ©2002 Dolezal Publishing/Tim Butler
Treating established viral infections is usually beyond the capabilities of even professional horticulturists. The most prevalent include “cabbage yellows,” which infects, weakens and can kill broccoli, Brussels sprouts, cabbage, cauliflower and kale; and tobacco mosaic, which generally stunts and kills tomatoes and its relatives. Your best bet for thwarting viral diseases is choosing plants that are resistant to the most common viral strains found in your region and varying your plantings in each bed from season to season.
If your vegetables should contract a viral disease, it’s important to prevent the infection’s spread. Once you recognize the disease condition, either uproot and burn all infected plants or remove it from your garden and dispose of it. Never compost diseased foliage, and avoid planting the same related vegetable in any bed that experienced infection during prior seasons.
By contrast, established fungal and bacterial infections are treatable. The most common 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 “Next Steps” at the bottom of the page for a link to identifying disease symptoms, as well as cures.)
Another condition caused by fungal disease that you may encounter (especially early in spring) is damping-off. (Several different fungi can also infect newly sprouted starchy seeds planted in moist, cool soil, all causing similar results.) 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 degrees F.
You can prevent most fungal diseases by proper spacing, ample air circulation and good watering practices. All fungal diseases stem from spores found naturally in the soil or carried by the wind. To germinate, the spores need to find a dark, moist environment with plant tissue for food. Keeping foliage dry is of the essence when it comes to 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 on a warm, dry day when the sun and wind will quickly dry the leaves. (Using these care techniques will prevent both downy and powdery mildew.)
You can further reduce the hazard of communicable plant diseases from your garden by avoiding large, single-species plantings and promptly removing all fallen, decayed leaves and plant matter from around your vegetables.
By inspecting your plants frequently and taking these simple precautions, your garden will be a healthy place filled with thriving vegetation and produce.
