Cannabis greenhouse disease diagnosis and integrated management, including powdery mildew, Botrytis, root disease, HLVd, sanitation, irrigation, airflow, and post-harvest microbial risk.
Diseases
Root Disease Complex
Root decline can involve oomycetes, fungi, low oxygen, temperature stress, salinity, chronic saturation, or combinations of these factors. Brown roots alone do not identify a pathogen.
What to look for
- Loss of fine roots or root-tip integrity
- Soft, sloughing, discolored, or poorly branched roots
- Reduced water uptake, wilting, or slowed growth despite moist media
- Root-zone odor or biofilm changes that require context rather than instant diagnosis
Important look-alikes
- Normal staining from some substrates or inputs
- Root aging
- Salt injury
- Low oxygen without an infectious pathogen
How to confirm
- Examine root texture and fine-root structure, not color alone
- Measure root-zone moisture, EC, pH, and temperature
- Review irrigation frequency and oxygen conditions
- Use laboratory testing when organism identification matters
Management principles
- Restore appropriate root-zone aeration and irrigation first when those are clearly abnormal
- Remove severely compromised plants when they threaten the rest of the crop
- Use pathogen-specific measures only when supported by evidence
Prevention
- Maintain clean irrigation and propagation systems
- Avoid persistent saturation
- Manage root-zone temperature
- Prevent cross-contamination through shared runoff or tools
Visual study guide
- Healthy versus compromised fine roots
- Root texture comparison
- Root-zone oxygen diagram
- Abiotic-versus-pathogen differential
Evidence & further reading