Symptoms of Septoria leaf spot can be seen on these infected tomato leaves.

Tomato fungal diseases can be a major problem in the home garden, causing frustration for the gardener. Symptoms include leaf spots, rots and wilts, leading to defoliation, sun scald, reduced yields and even death of the plant.

Microscopic fungal spores are spread by wind, water, insects, tools and humans.

In the Butler area, the two most common are early blight and Septoria leaf spot. To identify them, look at the size and shape of the spots on the leaves.

Large, irregular, “bull's-eye” spots with yellowing leaves are indicative of early blight. Many small, round spots with light centers are caused by Septoria leaf spot.

Pathogens for both blights overwinter on infected plant debris, where they can survive for up to three years. Initial infection occurs on lower leaves and spreads upward by rain or overhead watering.

Following are the top 10 ways to prevent, treat and minimize blight problems:

Rotate — Tomatoes, as well as eggplants, peppers and potatoes, should not be planted on the same soil more than once in three years. Ideally any crop preceding your tomatoes should be from the grass family, and an excellent choice for the home gardener is corn.

Select — Make certain the plants you bring home from the greenhouse are healthy. Use resistant or tolerant tomato cultivars. The Clemson.edu/extension website has a detailed list of cultivars that are resistant to a variety of tomato diseases, including blight.

Space — Placing your seedlings 2 to 3 feet apart promotes good air movement to allow drying after a rain. Overcrowding creates a dense canopy of foliage that locks in dampness. Try to orient your rows in the direction of the prevailing wind. Staking helps speed drying of plants and keeps fruits and leaves off the soil.

Mulch — Black plastic, straw or newspaper will act as a barrier between the soil and leaves and prevent rain splash up.

Fertilize — Healthy plants are less susceptible to disease. Fertilize when first fruits reach 2 inches in diameter and once a month thereafter. Use a water soluble or granular fertilizer. One tablespoon of granular fertilizer is placed 12 inches from the plant, since over-applied dry fertilizer can kill a tomato plant. Avoid heavy applications of nitrogen which will over stimulate green growth.

Eradicate — Pull weeds and any volunteer tomatoes, which may harbor fungus. Dense weeds rob plants of moisture, light and nutrients, and are also a haven for insects and disease.

Water — Never water from above, but do so at the base of the plant and early in the day to promote rapid drying of the foliage. Don't work in your garden when the tomatoes are wet, as handling can spread fungal spores.

Monitor — Inspect your tomatoes regularly for any signs of disease. Trim off and remove to your trash leaves and branches at the first sign of infection.

Spray — Chemical control is sometimes necessary and can be used preventively and to slow the progress, but never as a cure. Fungicides containing chlorothalonil, mancozeb or fixed copper (organic) used every seven to 10 days can help. They are available in garden centers under a variety of names. Be sure to follow the label directions.

Dispose — Sanitation is the most important way to prevent fungal diseases in your garden. At the end of the season, remove all crop refuse and place in black bags for the trash. Fungal spores overwinter on plant debris, including seeds. Next summer the blight cycle is restarted from the spores which remain on the soil surface and are then bounced onto your new tomato plants by rain or watering. It is best not to compost your tomato debris, as temperatures may not be high enough to kill the spores.

Careful planning and good garden practices can eliminate your need to proclaim next summer, “Oh, those darn leaf spots are back again!”