If you have chosen to farm hemp, then it's only a matter of time until you encounter disease in the field or greenhouse. The first thing to do is know which diseases are common in these crops so you can identify and prepare accordingly. We encountered a few different diseases after our first season growing just north of Las Cruces, New Mexico, in the Hatch Valley.
If you have chosen to farm hemp, then it's only a matter of time until you encounter disease in the field or greenhouse. The first thing to do is know which diseases are common in these crops so you can identify and prepare accordingly. Industrial hemp and marijuana are classified by taxonomists as the "Cannabis Sativa". Sativa is a member of "Mulberry family". Due to the difference in growing environments, hemp crops receive more exposure to different diseases than that of marijuana plants. But unfortunately, only little pathology work has been done on Cannabis Sativa crops. Lots of problems have still not been diagnosed.
Below is a list of the hemp disease detected by the "Nevada Department of agriculture" laboratory.
1) Fusarium Wilt:
Fusarium Wilt is one of the destructive diseases that are present in cannabis Sativa plants. It is caused by fungi. Fusarium oxysporum infects the vascular tissue and may cause plant death and wilt. The infection progresses systematically, which results in the pathogens being passed from parent plants to cutting or clone. The plant will exhibit poor growth and may wilt after adequate soil moisture.
- Vascular tissue turns dark brown
- Longitudinal and cross-section of lower stem reveals vascular browning
Preventing and treatment:
- Through periodic testing and monitoring
- Destroy infected trees and plants with bleach solution
2) Fusarium stem canker:
Some of the Fusarium species may cause stem rot and stem canker in addition to the vascular wilt. F. Solani and F. Oxysporum are found to have a strong association with the stem canker on hemp.
- Affected plants may exhibit cankers and dark lesion on stem
- White mold found on the top surface of cankered areas
- The rot of internal stem tissues
Treatment and prevention
- To avoid stem canker diseases, you should first select the field that not has been cultivated with different Fusarium-susceptible crops like sweet potato, melon, and tomato.
3) Pythium crown and root rot
Diagnostic characteristics: Pathogen known as "Pythium alphanidermatum" belongs to oomycetes. It attacks hemp crops and damping-off the seedling stage of crops or may cause the death of the plants during the season. Versions of this pathogens are believed to be vectored by leafhoppers and other pests and can quickly affect crop yields up to 50%.
- The early infection signs consist of curling, necrosis, and mild leaf yellowing
- Cankers and lesions may expand at Basel stem overtime
- Spread of infection from the crown area to the lower branches and stem
Treatment and protection
- Eliminate and reduce the disease with the help of approved fungicides or using a diluted bleach solution
4) Latent Fungal infection
Cannabis seeds carry some fungal pathogens with/without any visible seed damage. Some of the fungi may infect the hemp causes poor germination and affect the seedling viability. Some hemp seeds are being infected by the species of "Alternia" and consider as opportunistic and ubiquitous pathogens. One of the other fungus that causes fruit rot is Rhizopus. It also disinfects seedling health and seed germination.
- Close examination of seeds that may reveal some fungal growth during the test of routine germination
Treatment and protection
- Treat seeds via approved fungicides, and diluted bleach solution
Fungicides are generally not registered for any disease. Research is required to determine the efficacy of each product and the timing of an application. Crop rotation is the best and effective cultural practice that is used to avoid disease build-up. For more details, contact us.