Leaf Spot Showing up in Hemp Production
Several weeks ago a leaf spot was noted on a hemp plant. Samples were sent to Cornell University pathologist Dr. Gary Bergstrom. Dr. Bergstrom indicated that hemp is a host for a wide array of leaf spots. After completing diagnostic work at his lab, he diagnosed the sample as Septoria Leaf Spot. Because there are several species of Septoria associated with this disease, further diagnostics are underway to pin down the species and to verify pathogenicity on hemp. This is believed to be the first confirmation of this disease in New York.
Over the past 2-3 weeks the occurrence of this leaf spot has been noted in a number of hemp fields across several cultivars. The spotting appears to begin on lower leaves in the interior portion of the plant and moves upward as the plants grow and fill in. Dr. Bergstrom recommends good sanitation following harvest of this crop. The fungus can overwinter in infected crop debris. Moldboard plow remaining hemp tissue and rotate the field away from hemp for at least one year. Securing clean seed and transplants for future plantings is advised. There is no registered fungicide or biocontrol agent to be sprayed for control at this time.
We are interested in documenting the occurrence and severity of this leaf spot. Please email your observations to tr28@cornell.edu or to mru2@cornell.edu , a high resolution photo or two would be helpful as well.