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Patrick W. McMullen and Christine D. Smart
Signs and symptoms
Yellowing and browning of the leaves, wilting, and red to brown lesions on the crown may be visible. This disease most frequently occurs in cool, wet soils.
Causal organism
Vascular wilt is caused by Fusarium oxysproum, a soilborne fungal pathogen. This fungus has an extensive host range and can survive in the soil for years, making eradication difficult.
F. oxysporum reproduces asexually via micro and macro conidia. The pathogen enters the vascular tissue of the roots and grows within the root tissue. The mycelia of the fungus eventually clog the xylem vessel elements, preventing water flow to the shoots, and ultimately leading to wilting and plant death.
Management strategies
Successful management strategies can include a combination of cultural, biologic, and chemical approaches. Maintaining proper drainage in fields is critical. Avoid planting in wet and poor draining areas. While few products are currently approved for hemp, research is being conducted to determine the efficacy of plant growth promoting rhizobacteria and other fungicides.
Microbiome study
Soil microbes interact with plant roots directly. Between the host plant and microbe, a series of signaling pathways take place in response to plant stresses and physiological processes. This year we are conducting a microbiome analysis in partnership with Impello Biosciences to survey what the most abundant microorganisms are in the hemp rhizosphere and how they change over the course of the growing season. In these study, the microbial composition of soil cores from five different cultivars are being analyzed at three time points during the growing season. This can serve as foundational knowledge for future work studying the hemp rhizosphere and developing effective root growth promoting products.
