📈 Diseases of Sorghum and Pearl Millet

Sorghum (Sorghum bicolor) and pearl millet (Pennisetum glaucum) are vital dryland cereals in India, grown primarily in arid and semi-arid regions. Both crops face serious disease challenges that limit productivity.

Diseases of Sorghum

Grain Smut

Causal Organism: Sporisorium sorghi (syn. Sphacelotheca sorghi)

Symptoms:

• Individual grains in the panicle are replaced by smut sori (conical, grey-white structures) filled with dark brown teliospores
• Sori are covered by a tough peridium that ruptures at maturity
• Not all grains in a panicle are affected

Disease Cycle: Teliospores on seed surface germinate along with the seed. Mycelium grows systemically and replaces grain tissue.

Management:

• Seed treatment with Carboxin 75 WP (2 g/kg) or Thiram (3 g/kg)
• Use certified disease-free seed
• Grow resistant varieties

Grain Mold

Causal Organism: Complex involving Fusarium moniliforme, Aspergillus flavus, Curvularia lunata, and Alternaria alternata

Symptoms:

• Pink, white, black, or olive-green mold growth on developing grain in the panicle
• Grain becomes discoloured, shrivelled, and unfit for consumption
• Produces mycotoxins making grain hazardous

Favorable Conditions:

• Rain and humidity during grain filling and maturation
• Compact, drooping panicle types that retain moisture

Management:

• Grow varieties with open panicle type and hard grain texture
• Timely harvest at physiological maturity
• Spray Carbendazim (0.1%) at 50% flowering if rains are expected

Downy Mildew (Sorghum)

Causal Organism: Peronosclerospora sorghi

Symptoms:

• Systemic chlorotic streaks on leaves (alternating green and white stripes)
• Affected plants show excessive tillering and leafy panicles (phyllody)
• White downy fungal growth on lower leaf surface in early mornings

Management:

• Seed treatment with Metalaxyl 35 SD (6 g/kg seed)
• Rogue infected plants before sporulation
• Resistant varieties (e.g., CSH hybrids with resistance genes)

Anthracnose

Causal Organism: Colletotrichum graminicola

Symptoms:

• Circular to elliptical lesions with tan centre and red-brown margin on leaves
• Black acervuli (fruiting bodies) visible in lesion centres
• Also causes stalk rot and panicle infection

Management:

• Crop rotation with non-host crops
• Foliar spray of Mancozeb or Propiconazole
• Use resistant cultivars

Diseases of Pearl Millet

Downy Mildew (Green Ear Disease)

Causal Organism: Sclerospora graminicola

This is the most destructive disease of pearl millet in India, causing up to 30-40% yield loss in epidemic years.

Symptoms:

• Chlorosis on leaves — half-leaf symptom (lower half green, upper half chlorotic)
• Earheads transformed into green leafy structures (phyllody or "green ear")
• White downy growth on lower leaf surface

Disease Cycle: Oospores in soil serve as primary inoculum. Zoospores infect roots and seedlings systemically.

Management:

• Seed treatment with Metalaxyl 35 SD (6 g/kg)
• Grow resistant hybrids (e.g., HHB 67 Improved)
• Rogue infected plants before sporulation
• Avoid continuous pearl millet monoculture

Ergot (Sugary Disease)

Causal Organism: Claviceps fusiformis

Symptoms:

• Honeydew secretion (sweet, sticky liquid) from infected florets
• Later, dark brown to black sclerotia (ergot bodies) replace grains
• Sclerotia contain toxic alkaloids harmful to livestock and humans

Management:

• Remove and destroy sclerotia by salt water flotation
• Deep ploughing to bury sclerotia
• Spray Mancozeb at flowering stage

Smut of Pearl Millet

Causal Organism: Moesziomyces penicillariae (syn. Tolyposporium penicillariae)

Symptoms:

• Individual grains enlarged and converted into greenish to dark brown smut sori
• Sori are larger than normal grains and contain masses of teliospores

Management:

• Grow resistant hybrids
• Remove and destroy smutted ears before teliospore release
• Seed treatment with Carboxin

Summary Cheat Sheet