Ergot (Claviceps) in Grains & Grasses: Identification, Toxicity & Control

Ergot, caused by Claviceps species (primarily C. purpurea), replaces grain kernels with hard, purple-black sclerotia (ergot bodies) containing potent mycotoxins. Historically responsible for mass poisonings (St. Anthony's Fire), it remains a threat to livestock and humans consuming contaminated grain. Cool, wet springs favor infection during flowering.

Disease Cycle & Recognition

1. Overwintering: Sclerotia on ground or in stored grain.
2. Spring: Sclerotia germinate → mushroom-like stromata → release ascospores.
3. Infection: Spores land on open flowers (feathery stigmas) of rye, wheat, barley, triticale, grasses. Honeydew (sticky, shimmering exudate) appears—contains millions of conidia.
4. Secondary spread: Insects, rain splash move conidia flower-to-flower.
5. Sclerotia formation: Infected ovaries develop into hard, curved, purple-black bodies (2–20× kernel size) replacing grain.
6. Harvest: Sclerotia mix with grain; if not cleaned, enter food/feed chain.

Toxicity: Why It Matters

• Humans: Ergotism = vasoconstriction (gangrene, "St. Anthony's Fire"), convulsions, hallucinations, hyperthermia, immune suppression. Historically fatal.
• Livestock: Same acute signs; chronic exposure → reproductive failure (prolonged gestation, agalactia, neonatal death), especially horses.
• No antidote: Only treatment = immediate removal of contaminated feed + supportive care.

Management & Prevention

Field Practices

• Crop rotation: 1+ year non-cereal break (legumes, brassicas) reduces sclerotia.
• Deep plowing: Buries sclerotia >2" (prevents stromata emergence).
• Mowing field margins: Eliminates grass reservoirs before heading.
• Resistant varieties: Some rye/wheat lines have partial resistance.
• Seed cleaning: Gravity tables, color sorters remove sclerotia (commercial standard).

Harvest & Storage

• Scout fields pre-harvest; if ergot visible, harvest affected areas last/separately.
• Clean grain to <0.05% sclerotia by weight (FDA/action levels vary by commodity).
• Store dry (<13% moisture); sclerotia don't germinate in dry storage.

Livestock Protection

• Test feed if ergot suspected in region.
• Dilute contaminated grain with clean feed (only if below threshold).
• Never feed screenings/scalpings to animals—highest sclerotia concentration.

Ergot is a food-safety issue as much as a crop disease. Zero tolerance in human food; strict limits in feed. Clean seed, rotation, field hygiene, and grain cleaning are non-negotiable.