Common Plant Diseases: How to Identify and Treat Them

Plant diseases are usually caused by an infection brought by harmful organisms or parasites. While it’s hard to accurately know what kind of pathogen has infected your plant, you can still identify the disease through its symptoms. In early cases, you can still save your plant from further damage or even death; however, this requires correct diagnosis. This is to ensure that you will be applying the proper cure for the infected plant.

To help you properly diagnose your plant, here are some of the most common plant diseases, their causes, and ways how to treat them.

#1 Blight

Blights cause the sudden death of plant tissue; this will be apparent on the plant’s leaves, stems, and flowers. When a plant suffers from blights, leaves, stems, and flowers suddenly wither. They will also stop growing and will eventually result to the plant’s death. This disease is usually caused by wet and humid conditions.

Alternaria Blight (Early Blight)

This is a fungal blight that infects different types of plants: vegetables, fruit and shade trees, and even ornamental plants. It is called early blight in tomatoes, potatoes, and peppers. It is characterized by brown to black spots in leaves and sunken spots on fruits, stems, and branches. These spots enlarge and join together over a period of time; this results to the plant withering and eventually dying.

To counter this problem, dispose of the infected plants and spray potassium bicarbonate (baking soda) solution to the remaining plants.

To prevent plants from being infected by the Alternaria fungi, apply Trichoderma harzianum to the soil before planting.

Phytophthora Blight (Late Blight)

Phytophthora fungi usually infects lilacs, rhododendrons, azaleas, and holly. Symptoms of this disease include shoot diebacks, which make it a little difficult to distinguish from canker. This disease, however, starts showing signs on the leaves and crawls down to the stem, unlike cankers.

To control it, snip infected branches. This will help increase air movement in the plant.

On tomatoes, potatoes, and peppers, this disease is called late blight. It manifests through water soaked spots on the lower leaves; this will be mirrored with a formation of white hairy-like lesions on the undersurface of the leaves.

For late blight control, iit is important to remove and destroy infected plants. Snip off cankered shoots from shrubs as well. Eliminating infected plants is essential for this disease is highly infectious.

For preventive measures, keep the foliage as dry as you can. During humid weather conditions, frequently examine plants for any signs and symptoms. Early detection can help a lot to prevent further spreading of the disease. You can also opt to use preventive sprays of compost tea or Bacillus subtilis.

Fire Blight

This is a bacterial disease that infects fruits like apples and pears. An indication of a fire blight infected plant is reddish lesions on branches or stems. Limbs also tend to ooze an orange ooze during warm weather conditions. Symptoms start at the top part of the plant and crawls downwards, so it is important to look out for the early signs which are found in leaves and branches. It is characterized by brown or black spots on the tips of the leaves and branches. To counter fire blight, you can try to prune off infected branches at a late blight’s early stage. However, if disease has spread all throughout the plant, you might have to remove it to make sure the disease will not spread to neighboring plants. You can also use Streptomyces lydicus spray to reduce the spreading of bacteria.

Bacterial Blight

This type of blight is caused by cool and wet weather conditions. This disease is particularly severe on legumes in North America. Early symptoms show large, yellow spots on leaves, which eventually turns brown. It is also characterized by long, dark colored lesions on the stems.

To control bacterial blight, remove infected plants and give proper spacing between new plants. You may also plant resistant cultivars to prevent widespread of the disease.

#2 Canker

Cankers usually form on stems. It is identifiable by a discoloration on the plant’s stem. This disease causes shoots, stems, or trunks to wilt, which results to everything above it withering as well. Diebacks caused by cankers are a little difficult to distinguish from blights, but an important note to consider is that cankers start decaying from the stem, not  the leaves. To treat it, you should prune branches or stems with cuts and remove infected branches

#3 Rust

Common rust is a type of fungal disease that attacks roses, snapdragons, beans, tomatoes, and lawns. Symptoms usually start showing on leaves in the lower part of the plant.

During the early stage, the stem and underside of the leaves develop white, slightly raised spots. Over time, red orange spores will start to manifest on the leaves.

To treat it during its early stage, you can apply neem oil on the infected leaves to eliminate the spores that sprouted. But if the disease has considerably spread to some areas of the plant, you will have to remove all infected leaves and stems. Afterwards, you can apply copper spray and sulfur powder to reduce the growth of rust spores.

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