Warm, wet weather tends to be the perfect breeding ground for plant diseases. Lately we seem to be going from warm, wet weather to hot, dry weather. Once a plant disease has started, it is difficult to cure. The most common diseases you are likely to see are root rot, leaf spots and fruit rot. Here are some things you can do to prevent diseases from starting.
Site selection comes first – consider the needs of your plants. Your garden spot should have good drainage so roots don’t sit in water for extended periods. Wet “feet” or roots are the prime contributing factor to seedling, root and crown rot issues. The location should get at least 6 hours of sunlight a day and be open to air movement around the plants. Lack of ventilation around your plants creates a humid environment that allows many plant pathogens to flourish.
Crop rotation comes next. Continuing to plant the same family of vegetables in the same location contributes the buildup of pathogens in that location. You want to plant the same vegetable or those closely related in the same location once every 3 – 5 years. Longer rotations are best if soil borne issues like root or crown rot occur. See the below table for common vegetables grouped by family.
Third is using disease free or resistant seeds and/or transplants. Many diseases carry to the next plant generation through the seed, so if you choose to save seeds from year to year, only save those collected from healthy plants. Most store bought seeds are produced in the dry western area of the US where pathogens are less common so are sometimes more safe to use. If you prefer to use transplants to seeds, check to be sure they are healthy before purchase. Check both the leaves and the roots to ensure no disease symptoms are present.
Lastly is proper garden management practices. Constant wet soils cause diseases such as seed decay, damping-off, and root or crown rot while wet leaves contributes to foliar diseases like powdery mildew or downy mildew. Drip irrigation or soaker hoses both slowly release water at the roots where it needs to be and is the most efficient way to water as plants only need approximately 1 inch of water a week and only when nature doesn’t provided it for you. Mulching with straw, bark, leaves, plastic or shredded paper will prevent soil splashing onto plant during a rain event and keep produce off the ground. It will also help keep soil cool and moist, so you don’t have to water as often. Adequate fertility will help prevent many diseases so soil test at least 3 months prior to planting and follow recommendations given in the results to supply needed nutrients. Weeds are another disease source as pathogens or the insects that carry them often overwinter in weedy areas. Good weed control will reduce competition for nutrients and improve air ventilation around the garden, reducing trapped moisture. Most important of all is proper garden sanitation – remove any diseased plant material as soon as you see it to prevent the spread of pathogens throughout the garden. Also, remove all plant residue at the end of the growing season to prevent anything from overwintering in the garden. You should burn or otherwise destroy all diseased plant tissue and you can compost the healthy plant residue to add organic matter back to the garden later.