📈 Diseases of Groundnut

Groundnut (Arachis hypogaea), also known as peanut, is a major oilseed crop in India. It is susceptible to several fungal, viral, and soil-borne diseases that reduce both yield and oil quality. India is the second-largest producer of groundnut globally.

Tikka Disease (Early and Late Leaf Spot)

These two leaf spot diseases are the most common and widespread diseases of groundnut.

Early Leaf Spot

Causal Organism: Cercospora arachidicola (syn. Passalora arachidicola)

Symptoms:

• Sub-circular dark brown spots with a yellow halo on the upper leaf surface
• Spots are lighter brown on the underside
• Spots appear 30-35 days after sowing

Late Leaf Spot

Causal Organism: Cercosporidium personatum (syn. Phaeoisariopsis personata)

Symptoms:

• Circular, dark brown to black spots on the lower leaf surface — nearly black compared to early leaf spot
• No prominent yellow halo
• Appears later in the season (45-60 days after sowing)

Comparison Table

Management (Both Leaf Spots)

• Grow tolerant varieties (e.g., ICGV 86590, Girnar 2)
• Foliar spray of Chlorothalonil 75 WP (0.2%) or Mancozeb 75 WP (0.25%)
• First spray at 30-35 DAS, repeat at 15-day intervals
• Crop rotation with cereals; bury crop debris by deep ploughing
• Use groundnut varieties with longer dormancy to reduce volunteer plants

Rust

Causal Organism: Puccinia arachidis

Symptoms:

• Orange-brown uredial pustules on the lower leaf surface
• Pustules are small, circular, and may coalesce
• Severe rust causes premature defoliation and up to 50% yield loss
• Often occurs alongside late leaf spot in a disease complex

Favorable Conditions:

• Temperature: 20-25 degrees C with high humidity (>85%)
• Continuous rain during crop growth

Management:

• Grow resistant varieties (e.g., ICGV 86699)
• Spray Mancozeb (0.25%) or Chlorothalonil at pustule appearance
• Combined sprays for rust and leaf spots are cost-effective

Collar Rot

Causal Organism: Aspergillus niger

Symptoms:

• Pre-emergence and post-emergence seedling mortality
• Dark brown to black lesion at the collar region (base of stem near soil)
• Affected seedlings topple over and die within 2-3 weeks of sowing
• Crown and stem show black conidiophores and spores of the fungus

Favorable Conditions:

• High soil moisture at sowing, followed by dry spell
• Sandy soils with poor organic matter

Management:

• Seed treatment with Thiram + Carbendazim (1:1 at 3 g/kg seed)
• Seed treatment with Trichoderma viride (4 g/kg)
• Use healthy, good-quality seed with intact testa
• Avoid deep sowing

Stem Rot

Causal Organism: Sclerotium rolfsii

Symptoms:

• Wilting and drying of branches — initially one or two branches, later the whole plant
• White mycelial mat at the base of the stem near soil level
• Small, round, mustard-seed-like brown sclerotia on the mycelial mat and surrounding soil
• Root and pod rot in severe cases

Favorable Conditions:

• Warm, moist conditions (30-35 degrees C)
• Sandy loam soils with high moisture

Management:

• Deep ploughing and removal of crop debris
• Soil application of Trichoderma enriched FYM
• Seed dressing with Carboxin (2 g/kg)
• Crop rotation with non-host crops

Bud Necrosis Disease

Causal Organism: Peanut Bud Necrosis Virus (PBNV) — a tospovirus

Vector: Thrips (Thrips palmi and Scirtothrips dorsalis)

Symptoms:

• Necrosis of terminal buds and young leaves
• Axillary proliferation giving a bushy, stunted appearance
• Ring spots and mottling on leaves
• Petiole necrosis and reduced pod set

Management:

• Early sowing (before main thrips peak)
• Control thrips with Imidacloprid seed treatment or foliar sprays
• Border rows of fast-growing cereals (sorghum, pearl millet) as barrier crops
• Rogue infected plants

Summary Cheat Sheet