Emerging Cannabis sativa and hemp diseases, inoculum sources, field carryover, Neofusicoccum-associated disease, Sclerotinia white mold, southern blight, pathogen spread, and integrated disease-management context.
Diseases
Southern Blight
Southern blight, historically reported under the pathogen name Sclerotium rolfsii, has been reported on hemp and is favored by warm conditions. Crown collapse and surface fungal growth can resemble other root and stem diseases, so the pathogen should be confirmed when possible.
What to look for
- Rapid wilt or collapse associated with a lesion near the soil or media line
- White surface mycelium around the crown or nearby substrate under favorable conditions
- Small round survival structures that develop from pale to tan or brown as they mature
- Disease concentrated in warm areas or sites with a history of susceptible crops
Important look-alikes
- Sclerotinia white mold
- Fusarium crown disease
- Pythium-associated root decline
- Heat or drought stress that causes wilt without a crown lesion
How to confirm
- Inspect the crown and media surface, not only wilted foliage
- Look for fungal growth and survival structures while recognizing they may be absent early
- Review temperature, moisture, and field-history context
- Use laboratory identification for important outbreaks or uncertain cases
Management principles
- Remove severely affected plants and contaminated debris where appropriate
- Avoid moving contaminated soil or media into clean areas
- Reduce conditions that leave the crown persistently warm and wet when crop requirements allow
- Plan future site management around confirmed soilborne disease history
Prevention
- Know the disease history of outdoor sites and reused growing areas
- Use clean media and containers for protected cultivation
- Maintain sanitation around plant bases and remove infected residues
- Inspect crowns promptly when plants wilt despite adequate root-zone moisture
Visual study guide
- Southern blight crown lesion plate
- Sclerotia maturation close-up
- Southern blight versus Sclerotinia differential
- Soilborne inoculum movement diagram
Evidence & further reading