— Written By Lindsey Thiessen

Hemp Leaf Spot Troubles

North Carolina industrial hemp producers are combatting a leaf spot concern that is brought on by Exserohilum rostratum. This illness was initial identified for the duration of the industrial hemp pilot plan in 2017, and has not been widespread in the final two years. In the final week, nevertheless, we are seeing this illness in a number of hemp strains of hemp across the state. Other leaf spots might appear equivalent to this illness, and correct diagnosis is critical.

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 modest and round with dark brown margins and a gray-brown center. As lesions age, spores might be made inside the gray-brown center, and appear like fine ground pepper flakes. Lesions might coalesce to kind bigger, irregular-shaped lesions.

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

Other equivalent ailments consist of bacterial leaf spot, Fusarium leaf spot, and Septoria leaf spot. North Carolina has not had considerably incidence of Septoria leaf spot, but there is info from University of Kentucky accessible 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 exact same Fusarium spp.

Management Methods

There are presently no chemical management techniques that are helpful and legal to apply in industrial hemp. Cultural practices might assistance minimize incidence by removing the pathogen from the production method or producing situations significantly less appropriate for development of the fungus.

  • Preserve weed-no cost fields to limit fungal survival on grasses or other weedy hosts
  • Destroy crop debris at the finish of the developing season to limit overwintering inoculum
  • Enhance air flow by way of the plant canopy to limit humid situations that favor fungal development

Have additional inquiries?

For additional assistance on managing industrial hemp foliar ailments, make contact with your cooperative extension agent.