Common Peanut Plant Diseases:
How to Identify and Treat

Peanuts are a popular and nutritious crop that is cultivated all over the world. However, like any plant, peanuts are susceptible to various diseases that can hinder their growth and reduce yields. It is crucial for farmers and gardeners to be able to identify these diseases early on and take appropriate measures to control them. In this article, we will discuss some of the most common peanut plant diseases, how to spot them, and effective treatment options.

1. Early Leaf Spot

Early leaf spot is one of the most prevalent diseases affecting peanut plants. It is caused by the fungus Cercospora arachidicola and can severely impact yield if left untreated. The disease first appears as small, dark brown spots with yellow halos on the lower leaves of the plant. As it progresses, the spots enlarge and coalesce, eventually leading to defoliation.

To control early leaf spot, it is essential to practice good crop rotation and maintain proper spacing between plants to improve air circulation. Fungicides containing active ingredients such as chlorothalonil or azoxystrobin can also be applied preventively or at the first signs of infection.

2. Late Leaf Spot

Late leaf spot is another fungal disease that affects peanut plants. It is caused by the pathogen Phaeoisariopsis personata and typically appears later in the growing season compared to early leaf spot. The symptoms include circular or irregular-shaped lesions with a reddish-brown color on both sides of the leaves.

To manage late leaf spot, similar control measures as those for early leaf spot can be taken. Additionally, cultivars with improved resistance to this disease are available and should be considered for planting.

3. Tomato Spotted Wilt Virus

Tomato spotted wilt virus (TSWV) is a devastating disease that affects a wide range of crops, including peanuts. It is transmitted by thrips, tiny insects that feed on plant sap. TSWV causes a variety of symptoms, including chlorotic spots, necrosis, and stunted growth. Infected plants may also exhibit curled or distorted leaves.

Preventing thrips infestation is crucial for managing TSWV. This can be achieved by using reflective mulches, which repel thrips, or by applying insecticides specifically targeted at these pests. Additionally, removing infected plants from the field as soon as symptoms are noticed can help prevent the spread of the virus.

4. Peanut Mottle Virus

Peanut mottle virus (PMV) is another viral disease that affects peanut plants. It is transmitted by aphids and causes characteristic mottling on the leaves, hence its name. Infected plants may also exhibit stunted growth and reduced pod development.

To control PMV, it is essential to manage aphid populations. This can be done through the use of insecticides or by introducing natural predators such as ladybugs and lacewings to the field. Removing infected plants and practicing good weed control can also help reduce the spread of the virus.

5. Sclerotinia Blight

Sclerotinia blight, caused by the fungus Sclerotinia minor, is a destructive disease that affects many crops, including peanuts. The disease usually appears during periods of high humidity and temperatures between 68°F and 86°F (20°C and 30°C). Infected plants show water-soaked lesions on stems, petioles, and pods, which later become brown and turn into fluffy white masses of fungal mycelium.

Controlling sclerotinia blight requires a combination of cultural practices and fungicide applications. Good crop rotation, avoiding excessive plant density, and applying fungicides containing active ingredients such as boscalid or thiophanate-methyl can help manage this disease effectively.

6. Root-Knot Nematodes

Root-knot nematodes are microscopic roundworms that infect peanut plants and cause significant damage to the roots. Infested plants often exhibit stunted growth, yellowing leaves, and reduced pod development. The roots may also develop characteristic swellings or galls.

To manage root-knot nematodes, it is crucial to practice crop rotation with non-host crops and use resistant peanut varieties whenever possible. Soil solarization, a process of heating the soil using transparent plastic sheets, can also help reduce nematode populations in the field.

In conclusion, peanut plant diseases can have a detrimental impact on crop yields if not properly managed. Early identification and appropriate treatment measures are essential to prevent the spread and development of these diseases. By implementing good cultural practices, such as crop rotation and proper spacing, and utilizing effective fungicides and insecticides when necessary, farmers and gardeners can protect their peanut plants and ensure healthy harvests.