Around the Countryside
Disease Management in the Home Garden
Marion Barnes, Senior County Extension Agent
Clemson University
Plant diseases can be a problem in the home garden, especially during warm, wet weather. Most vegetables are susceptible to at least a few diseases, with some diseases being more problematic than others. Common vegetable diseases include leaf spots, root diseases, and fruit rots, to list a few. The four types of organisms responsible for most diseases are fungi, bacteria, nematodes, and viruses. They are often referred to as pathogens or plant parasites.
Plant diseases caused by fungi and bacteria are more prevalent during warm weather and frequent rain showers or heavy dews. Viral diseases of vegetables mainly occur during the summer when insects that vector (transmit) these diseases are more active. Nematodes can be present in your soils all year long but are most active and feed on the roots of your vegetables during times of warmer temperatures. High numbers of nematodes will reduce yields and plant growth.
To reduce the impacts of plant diseases, home gardeners should consider the following cultural practices described below.
Site selection
Site selection is one of the essential components of a successful garden. The site should be in a
well-drained, open, sunny location. Avoid wet or poorly drained soils that can contribute to root and seedling diseases. Shade and dense vegetation around the vegetable garden can restrict airflow and encourage plant diseases. Full sun speeds the drying of foliage and reduces the incidence of most foliar diseases.
Crop rotation and fallowing
Continuous plantings of crops of the same plant family in the same spot can increase pathogen buildup.
In general, to reduce pathogen buildup in the soil, consider growing the same vegetable or closely related vegetables in the same spot once every three to five years. Longer rotations or other management methods may be needed to combat soil-borne pathogens such as nematodes or root diseases caused by fungi such as Rhizoctonia, Pythium, or Phytophthora.
Fallowing (leaving land idle without a crop for several seasons) can disrupt soil pathogens’ life cycle by exposing then to a non-host environment. With this interruption, pathogens are unable or slow to build to damaging levels.
Disease-free seed and transplants
Many plant diseases can be seed-borne. If you are saving seed, consult seed saving guides and only keep the seed from healthy, disease-free plants. Diseases like bacterial and fungal leaf spots and fruit spots can contaminate their host plants’ seed with disease-causing fungal spores and bacterial cells. When a contaminated seed is planted, the new plant can be infected. Save seed from only healthy disease-free plants or purchase seed from reputable seed sources. If you start your garden from transplants, examine them closely and select plants that appear disease and insect-free.
Disease-resistant varieties
Planting resistant varieties are the most effective method of managing vegetable diseases. Resistance is a general term, and resistant varieties can be either partially or entirely resistant depending on the condition and the variety. Most seed catalogs list resistant traits of their vegetable varieties, usually noted by abbreviations. The most resistant varieties are F1 hybrids. Open-pollinated or heirloom varieties are generally not labeled as disease-resistant. Some important disease resistances to consider when purchasing seed are:
- Tomatoes: Fusarium wilt (F2, F3), nematodes (N), tomato spotted wilt virus (TSWV),
late blight (LB).
- Cucumbers/ squash: Powdery mildew (PM), downy mildew (DW), and anthracnose (A).
- Beans: Bean mosaic Virus (BMV), anthracnose (A)
Planting date management
Planting dates can be used as a disease management tool. Planting seeds when soil temperatures are not optimum for germination can increase seedling diseases. Planting dates can also be adjusted to avoid times of increasing pest pressure. For example, early planted sweet corn usually has less corn ear-worn (CEW) damage, and late-planted squash can see increased vine borer and pickle worm damage. Following recommended planting dates for the particular vegetables being grown can reduce disease and pest pressure.
Soil testing
Soil is the foundation of productive and healthy plants. Soil fertility, temperature, and moisture influence soil pathogen’s ability to survive and infect plants. Have your soil tested annually.
Water management
Wet soils can lead to soil-borne diseases such as seed decay, damping-off, and root and crown rots. Wet foliage increases foliar diseases. To promote healthy root systems, water deeply with the equivalent of
One inch when needed, depending on rainfall and soil type. Hand watering is adequate on small gardens as long as watering is directed at the plant’s base and not on foliage. Drip irrigation is more efficient in larger areas.
Nematode management
Nematodes are microscopic roundworms that live in the soil. Certain species can harm plants by injuring and feeding on their root systems. Nematode damage is not always apparent and may go undetected. If you suspect a problem, have your soil tested for nematodes. Since there are no nematode pesticides labeled for use in the garden, cultural practices must be employed. Nematode management practices may include:
- Rotating to non-host crops
- Planting resistant varieties
- Planting nematode suppressive cover crops
- Increasing soil organic matter and microbial diversity
Sanitation
Sanitation involves practices to reduce pathogen populations and reduce their spread. Many pathogens survive between crops on old plant residue, so it is crucial to remove as much of the old residue (plant material) as possible. Avoid composting plant material from diseased plants.
Pesticides
Synthetic pesticides should be the last defense against diseases once all other preventive measures have failed. Home gardeners have fewer pesticide options variable as compared to commercial producers. However, many gardeners choose to use biopesticide products that are more environmentally friendly than traditional synthetic pesticides. Most vegetables can be grown most years in the home garden without using pesticides. When using pesticides, always read the label and follow directions. Remember, the pesticide label is the law.
In summary, healthy plants are the best prevention against plant diseases. Use proper cultural practices to maintain and promote healthy and vigorously growing plants. For more information on disease control in the home garden contact your local Clemson Extension Office. Information for this article was taken in part from Disease Management in the Home Vegetable Garden by Elizabeth Little, Home Garden/ Small Farm Plant Pathologist, University of Georgia Extension Service.
Clemson University Cooperative Extension Service offers its programs to people of all ages, regardless of race, color, gender, religion, national origin, disability, political beliefs, sexual orientation, gender identity, marital or family status and is an equal opportunity employer
