Plant Disease Prevention
Keep plants healthy.
This starts with soil that is rich in humus, drains well, and has ample nutrients. Amend soil regularly with compost and apply organic mulches continually to enrich your soil. Test soil samples for nutrient levels and pH, and make necessary adjustments. Apply only as much fertilizer as you need, since excess can cause growth imbalances that weaken plants and invite disease. Cull plants that are diseased to prevent pathogens from spreading.
Buy treated seed.
Seed may come pretreated with a dusting of fungicide. This coating will help prevent the seed from rotting in the soil before germination and help protect the emerging seedling from a harmful “damping off” pathogen that girdles and kills young plants shortly after they emerge. If seed rot or damping-off has been a problem in your garden, treating seed with a fungicide will help.Make sure seeds, transplants, and propagating material are disease-free.
Start with healthy plant material to help plants get established quickly. Unhealthy plant material will never yield as much as healthy material. Worse, plants may die while they are still young. Reputable seed companies sell only disease-free plant materials. They treat some seeds with hot water to remove infectious agents. They test others to reduce the risk of seed-borne viruses. When shopping for transplants or other propagating material, take time to examine the plants to make sure they are healthy and vigorous. If you save your own seed, harvest it from healthy plants and dry it thoroughly. Store seed in airtight containers in a cool, dry place.
Keep a close watch for pests, especially aphids and leafhoppers, which can spread diseases as they feed. Their feeding can also create entry points for rot organisms. Also, plants that are weakened by pests are more susceptible to disease.
Choose a sunny, well-drained location.
Most vegetable crops thrive in full sun. Shady, poorly drained sites produce weak, spindly plants that are easy targets for disease organisms. Even if such plants survive free of disease infections, they will not yield as much as strong, healthy plants. . Avoid wet and poorly drained soils. Excessive soil moisture will contribute greatly to disease, especially seedling, root and crown diseases. . Full sun speeds drying of the foliage, which can reduce the incidence of most foliar diseases.
Weed your garden. If you allow weeds to get our of hand in your garden, the competition for nutrients and moisture can weaken crop plants, leaving them susceptible to infection. Crowding also reduces air circulation, allowing moisture to remain on plants long enough to allow fungal and bacterial pathogens to infect plants.
Improve the soil.
When your only choice for a garden site has heavy, wet soil, plant in raised beds or ridged rows so that the soil around your plants’ roots won’t be waterlogged. Heavy, wet soils discourage healthy root growth and encourage root rots. If you plant a garden on a slope, build terraced beds to reduce soil erosion over delicate, young plants and newly sown seed. Soils that are dry and sandy can be mulched with straw, grass clippings, black plastic, or other materials to retain moisture. A soil that is favorable to healthy root development supports the growth of healthy plants.
Water plants carefully.
For best growth, plants usually require about 1 inch of water per week. If you don’t get enough rain, water your garden. Water plants in the morning so that the foliage dries quickly. This reduces the spread of disease. Avoid using sprinklers if possible because they promote the spread of leaf, flower, and fruit infections. Trickle irrigation is a better choice because it delivers water directly to the soil without getting the rest of the plant wet. It also doesn’t splash soil onto the plants, which can move pathogens from the ground onto the plant. (Mulches can also help reduce soil splashing.)
Don’t over- or under-fertilize.
Plants that are fertilized properly at planting and during the season will grow better and be healthier. Use a complete and balanced fertilizer or incorporate well-rotted manure or rich compost into the soil. Avoid over-fertilizing because it can damage roots.
Space plants to allow air circulation.
High humidity and moisture favor the development of plant diseases. Allowing enough room for plants to grow and for air to circulate around mature plants reduces humidity and encourages rapid drying of plants after rain.
Clean up debris.
Always remove and destroy or discard (in the trash) plant material that shows signs of disease. Work in the garden when plants are dry because moisture on plants aids the spread of diseases.
Unless you have an active, hot compost pile, composting may not effectively eliminate diseases from plant residues under New York climatic conditions. At the end of the growing season, clean up all crop residues. Disease agents overwinter in debris and may infect new plants the following season.
Active composts should suppress pathogens that are often found on leaf material. Composting these plant parts is highly recommended. Diseased tubers, bulbs, and similar plant parts, on the other hand, should be discarded and not composted. These plant parts can survive longer periods in the compost pile before breaking down and may actually begin to grow within the compost pile.
Plant a fall cover crop.
After cleaning up the garden, sow a cover crop such as winter rye that will grow that fall and protect the topsoil during winter. The following spring, plow the cover crop back into the soil to enrich it with fresh organic matter. Cover cropping can help reduce populations of soil-borne disease agents. Noninfectious microbes flourish when cover crops are returned to the soil and tend to inhibit the disease-causing microbes.
Crop rotation is very important in reducing losses to vegetable diseases.Successive plantings of one crop family in the same area promotes the buildup of disease agents in the soil, making disease problems more severe over time. Rotate plants to different areas of the garden to help reduce losses caused by soil-borne disease agents. Only grow the same type of vegetable or closely-related vegetables in the same soil once every three to five years
Frequently Asked Questions