Authors: Nicholas Dufault, Zach Eldred, Keir Hamilton, Kevin Korus; UF/IFAS Extension State Specialist, Doctor of Plant Medicine Students, and Alachua County Agent

Florida’s industrial hemp growers face many challenges when developing a pest management plan. One challenge that if often overlooked, until it is too late, is disease management. While there are currently not many options available for disease control once a crop has been established, it is still important to monitor and identify diseases, so management plans can be developed or modified in the future.

Diseases currently identified in Florida

There are many industrial hemp diseases that have been reported in other states (e.g. Kentucky, North Carolina, etc.) producing this crop and there are still many unidentified diseases (e.g. hemp viruses) too. The industrial hemp pilot program has been established to help understand the crop’s production in Florida, as well as to identify common pest and disease problems throughout the state. So far, a total of 5 diseases have been positively identified on industrial hemp in Florida, with at least 11 observed and requiring confirmation. It is likely that this number will increase as production increases in the state, so it will be important to determine which diseases are most predominant. A list of the foliar, stem, and root diseases observed in Florida can be found in Tables 1 and 2 (click on images to enlarge to full screen). This list will be updated on regular basis.  More information on the diseases can be found at the Hemp Diseases of Florida website.

table 1 Hemp Foliar Diseases

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Table 2 Hemp Stem & Root Diseases

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To date, there have been no viral pathogens identified as a causal agent of disease in hemp, though this does not suggest that viral pathogens are not present. Growers should always pay special attention to their crops, and monitor for insects that commonly transmit viral diseases (e.g. whiteflies and/or thrips). Additionally, more information regarding pests on hemp can be found on the UF/IFAS Insect and Mite Pests of Hemp website.

This is not an exhaustive list of all diseases affecting industrial hemp in Florida or the US. More information on these, and others diseases to come, can be found on the Diseases of Hemp in Florida website. This website will continue to be updated as more information becomes available, and should assist in the identification of industrial hemp diseases in Florida.

Disease management starts with prevention

Once a hemp plant becomes infected with a pathogen, whether it is fungal, bacterial or viral, it is not curable, so suppression is typically the best management that can be expected. This is why prevention is key to any management program, however, disease prevention in hemp requires and integrated management approach. This means using a combination of cultural, varietal or plant stock, and environmental management techniques. Table 3 lists some common management techniques for each category.

Table 3 hemp disease management

More information can be found at the UF/IFAS Industrial Hemp Pilot Project

What about pesticides? According to the EPA’s website there have been 47 pesticide products registered for use on industrial hemp in the U.S. This registration does not guarantee that is has been labeled for use in Florida, so it is always important to read the label and/or contact your local extension office for a product availability and use. Many of these products have both insecticidal and fungicidal activity, however, their efficacy, especially after pest/disease establishment, is primarily for suppression.

Disease identification is key to management

The key step prior to developing a disease management plan begins with obtaining an accurate disease diagnosis or identification. With industrial hemp being a relatively new crop, knowing which pathogen is affecting your crop will not only improve your capacity for management, but will also provide valuable information for developing future disease identification and management protocols in hemp.

If you suspect, or have any questions regarding a disease in your production system, you are encouraged contact your local extension agent, or send a sample directly to a diagnostic lab. Finally, if you are looking for more general information regarding industrial hemp production in Florida, you can refer to the FDACS website:  Hemp in Florida.

Nicholas Dufault