Disease control can be a challenge in any garden. It helps to have a general understanding of them and how they can best be prevented. The primary types of plant diseases are viral, bacterial and fungal. Viruses usually occur on new growth. Bacterial or fungal infections usually occur on older leaves. Some symptoms are stunted growth, spots on leaves, rotten fruit or wilting. All three diseases are more active during times of high humidity or light, steady rain. Plant foliage never completely dries during these periods. This creates a perfect environment for disease to take hold.
Nematodes are also included in the disease group. These very small, worm-like creatures feed on roots. They can stunt growth and cause extensive damage if not controlled. However, there are many different types of nematodes, some of which are actually beneficial.
To help thwart diseases, keep your plants healthy. A healthy plant is naturally disease-resistant. Fertilize and water regularly, but avoid getting water directly on the leaves. Soaker hoses are an ideal way to help keep foliage dry while watering. Also, you may want to consider growing disease-resistant varieties.
All gardeners know that mulch helps conserve water and keeps roots cooler. But be sure to use clean mulch. Do not re-use mulch from season to season as diseases as well as pests can winter-over. Also, do not compost any diseased plants as you are likely to recycle the disease right back into your garden.
In addition to using clean mulch, keep your garden clean. Promptly remove dead or dying plants. It’s also a good idea to thin any thick foliage so that your plants receive adequate air circulation. Trellis as many crops as you can. Keeping fruit and vegetation off the ground helps prevent rot and keeps plants dry.
Rotate your crops. It is a good idea to plant vegetables in the same family in a different location each season. (For example, avoid planting Nightshades such as tomatoes in the same bed that potatoes were recently grown.) This helps break the reproductive cycle of the disease and helps prevent the depletion of nutrients in the soil.
Another way to keep plants healthy is to make sure your soil has good drainage. Soggy soil will cause root rot and will allow diseases to flourish. An excellent way to create good drainage is to grow your vegetables in raised beds and to use organic amendments such as manure or compost.
Nematode populations can be discouraged by keeping your soil rich in organic matter. Once a fungal, bacterial or viral infection appears, it can be treated organically with copper or sulfur-based compounds. Regular applications are critical to successful control. Sometimes it helps to be proactive. I live in the humid South where diseases can set in overnight and run quickly through the garden. To keep tough diseases such as bean rust under control, I start spraying with a copper-based compound early in the season, before the rust appears.
All in all, the very best way to control plant diseases is by being attentive. While it is not practical to expect a totally disease-free garden, you can keep problems to a minimum by following these tips.