How to Treat Common Plant Diseases

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There’s nothing worse than working hard in your garden only to discover that disease has ruined part of your crop. So much time is involved in maintaining a garden, and no one wants to put forth all that effort for no reward. To have a healthier harvest, let’s look at some of the most common plant diseases and how to prevent and treat them.

Early Blight

This disease affects tomatoes, especially in Mississippi. The first symptom is dark brown or black circular spots, which appear on older leaves. As the disease spreads, the leaves will turn yellow and begin to wither before falling off.

Often, only the newest leaves of the plant will stay green and appear healthy. In most severe cases of early blight, the plant will lose all of its leaves. Target-like sunken spots may develop on tomato branches and stems.

Prevention measures include the following:

  • Select the proper seeds.

  • Use an organic seed treatment before planting.

  • Use organic fungicides.

  • Dispose of infected plants.

  • Avoid planting in areas that were infected with early blight the year before.

Blossom-end Rot

In my early gardening years, blossom-end rot was my most common problem. It occurs on tomatoes most often but may also be a problem for squash, peppers or watermelon. And it’s more common on plants that are halfway grown.

The first sign of this disease is the appearance of small, water-soaked spots that eventually develop into dark-brown, leathery spots that can involve half of the fruit. The surface of the spot will begin to shrink and become sunken.

Blossom-end rot is more likely to occur when plants grow quickly early in the season but are then subjected to extensive dry weather. It’s actually caused by a lack of calcium in the growing plant, but you can maintain a soil pH of 6.5 to prevent this. Also, avoid excessive applications of nitrogen. Irrigate and mulch regularly to encourage uniform soil moisture.

Southern Blight

Unfortunately, southern blight attacks most gardens and is difficult to control. The fungus that causes this disease attacks plant parts like stems, roots, leaves or fruit that are in contact with the soil or just under the surface.

The first symptom is a yellowing of the leaves and wilting. It begins in the lower leaves. In moist, warm weather this white fungus may appear on the lower stem near the soil. After this stage, tan-to-dark-brown, mustard seed-like structures called sclerotia start to form in the mold.

As this disease develops, it will spread to other plants near the infected one and can ruin an entire crop. To stop the spread of disease, remove the infected plant as soon as you notice it. Take six inches of soil in depth as well as six inches from the stem.


Sometimes referred to as leaf spot disease, this fungal infection is fairly obvious. The infection causes small, dark and water-soaked lesions that often become covered with slimy pink masses of spores, especially in moist, warm weather.

Anthracnose can be spread by garden tools, so I recommend using bleach diluted in water to disinfect them. This disease can destroy your crop in a matter of days, so taking steps to prevent it and acting swiftly is a must.

Dispose of any infected plants and organic matter near the infected plant, including dead leaves that can carry the disease. Purchase disease-free seeds to prevent anthracnose, and control infections using an organic sulfur-based fungicide.

Buying disease-free and disease-resistant seeds can go a long way toward keeping your garden healthy, but doing so doesn’t mean you shouldn’t watch for trouble. Know what your crops should look like so you can easily detect when something is wrong. If a problem arises, act quickly. Timing can mean the difference between losing a plant and losing your harvest.