Root Ailments Prevalent in Industrial Hemp

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— Written By Lindsey Thiessen

Root, Crown, and Stem Rot

Root, crown, and stem rots are becoming observed in industrial hemp stands across North Carolina. Though numerous of these pathogens are opportunistic, several are extreme complications that can have impacts on future crops. At present, there are no chemical management tools accessible to producers that will economically minimize these pathogen pressures. Moreover, the use of chemistries off label may perhaps outcome in crop harm from possible phytotoxicity effects or crop rejection from purchasers. This info is to serve as a guide to identifying complications and present some cultural practices that may perhaps minimize effect by these pathogens.

Fusarium wilt and crown rot (Fusarium spp.)

Fusarium wilt and crown rot are brought on by Fusarium spp. Damages related with Fusarium wilt and crown rot involve yellowing and wilting of leaves (Fig. 1) and vascular discoloration (Fig. two). Root rots brought on by Fusarium spp. are most typically related with other injuries to plant roots (i.e. environmental circumstances, nematode injuries, mechanical injuries from cultivation). Plants that are more than-irrigated or flooded from intense climate circumstances may perhaps be much more prone to damages. Similarly, insect or nematode injuries may perhaps make wounds in the roots and crowns of plants that permit the fungus to colonize plants.

To minimize losses from Fusarium wilt or crown rot:

  • Limit damages to roots by nematodes or root-feeding insects
  • Steer clear of physical injuries to reduce stems or roots of plants with farming gear
  • Eliminate impacted plants from fields and destroy crop debris rapidly just after harvest to limit inoculum buildup

Figure 1. Wilting of hemp plant brought on by Fusarium spp.

Fusarium wilt vascular discoloration

Figure two. Vascular discoloration of hemp crown brought on by Fusarium spp.

Southern Blight (Sclerotium rolfsii)

Southern blight/Southern Stem Rot is brought on by Sclerotium rolfsii, which has a wide host variety like vegetable, fruit, ornamental, field crops, as properly as several weed species that may perhaps persist in the field. This illness causes the leaves to yellow and wilt, and the reduce stem shows indicators of necrosis (Fig. three). In heavily infested plants, smaller, brown BB-shaped sclerotia (overwintering structures) can be identified on white fungal mats at the base of stems (Fig. three). This illness is favored by hot, humid circumstances, which have been persistent this expanding season.

To minimize losses from Southern Blight:

  • Limit damages to roots by nematodes or root-feeding insects
  • Steer clear of physical injuries to reduce stems or roots of plants with farming gear
  • Eliminate impacted plants and any fungal structures that are surrounding the plants from fields and destroy crop debris rapidly just after harvest to limit inoculum buildup
Southern Blight of Hemp

Figure three. Industrial hemp crown impacted by Sclerotium rolfsii. Photo courtesy of Eli Snyder, Caldwell County Extension Agent

Pythium Root Rot (Pythium spp.)

Root rots brought on by Pythium spp. are prevalent in circumstances with excess moisture or with a history of Pythium root rot. This fungal-like organism has spores that can move in water. Excess water surrounding hemp root systems make them much more susceptible to illness, and the water permits pathogens like Pythium spp. to access the roots much more effortlessly. This can be identified in greenhouse and field production systems, and can result in substantial harm to plants. Plants yellow and wilt, and the roots come to be brown and necrotic. For much more info on Pythium root rot, see the Pythium Root and Crown Rot of Industrial Hemp Reality Sheet.

To minimize losses from Pythium Root Rot:

  • Limit damages to roots by nematodes or root-feeding insects
  • Steer clear of excess water about roots and prevent watering from ponds, lakes, or streams as they can be a supply for this pathogen
  • Eliminate impacted plants from fields and destroy crop debris rapidly just after harvest to limit inoculum buildup

For distinct queries relating to industrial hemp illness management, make contact with your neighborhood cooperative extension agent.



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