Exserohilum Leaf Spot Causing Complications in NC Hemp

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— Written By Lindsey Thiessen

Hemp Leaf Spot Complications

North Carolina industrial hemp producers are combatting a leaf spot problem that is brought on by Exserohilum rostratum. This illness was very first identified in the course of the industrial hemp pilot system in 2017, and has not been widespread in the final two years. In the final week, nevertheless, we are seeing this illness in many hemp strains of hemp across the state. Other leaf spots might appear related to this illness, and precise diagnosis is vital.

Symptoms of Exserohilum Leaf Spot

This illness can have an effect on any portion of the plant, which includes stems, flowers, and leaves. The leaf spot is most distinct (Fig. 1) as lesions are little and round with dark brown margins and a gray-brown center. As lesions age, spores might be developed inside the gray-brown center, and appear like fine ground pepper flakes. Lesions might coalesce to type bigger, irregular-shaped lesions.

Figure 1. Leaf spots on industrial hemp leaves brought on by Exserohilum rostratum.

Other related ailments involve bacterial leaf spot, Fusarium leaf spot, and Septoria leaf spot. North Carolina has not had a great deal incidence of Septoria leaf spot, but there is information and facts from University of Kentucky out there for Septoria Leaf Spot.

Bacterial leaf blight

Figure two. Bacterial leaf spot and blight on industrial hemp leaves characterized by angular lesions.

Fusarium leaf spot

Figure three. Fusarium leaf spots on hemp leaves. Wilting of plant brought on by a stem canker from the similar Fusarium spp.

Management Approaches

There are at the moment no chemical management methods that are powerful and legal to apply in industrial hemp. Cultural practices might support lower incidence by removing the pathogen from the production method or creating situations much less appropriate for development of the fungus.

  • Keep weed-absolutely free fields to limit fungal survival on grasses or other weedy hosts
  • Destroy crop debris at the finish of the expanding season to limit overwintering inoculum
  • Strengthen air flow by way of the plant canopy to limit humid situations that favor fungal development

Have additional queries?

For additional support on managing industrial hemp foliar ailments, get in touch with your cooperative extension agent.



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