Legume smuts

The fungus's life cycle includes the formation of spore galls that develop directly within the plant's reproductive organs. The teliospores are characterized by high viability and can persist in the soil for several years.

Infection is transmitted both through contaminated seeds and soil, where fungal spores remain active even in the absence of a host plant. The depth of spores in the soil directly influences the intensity of seedling infection.

The fungus mycelium develops inside the plant tissues, gradually invading the vascular system and reproductive organs. This makes the disease difficult to manage during the later stages of the growing season.

The biology of Thecaphora deformans is closely tied to the host's development phases, with the fungus synchronizing its activity with the legume crop's growth periods for maximum seed infection.

The first sign of the disease is the characteristic deformation of flowers and pods on the affected plant. They become thickened, twisted, and develop an atypical shape, which gives the pathogen its name.

Inside the affected pods, instead of healthy seeds, a dense mass of fungal spores is formed, known as spore galls. Initially, they are light in color, but as they mature, they turn dark brown or black.

Plants affected by smut often show stunted growth and a generally suppressed appearance. Depending on the severity of the infection, premature yellowing and leaf drop may occur.

In the field, infection patches are easily identified by the lack of normal fruit production on individual bushes. When pods are opened, a complete absence of seeds is observed, replaced by spore powder.

Unlike other smut species, this pathogen localizes strictly in the reproductive organs, so vegetative parts of the plant may remain green longer than healthy individuals due to the disruption of nutrient flow.

The development of the fungus is favored by moderately humid weather during the seed germination and legume organ formation stages. The optimal soil temperature for infection usually ranges from 15 to 22 degrees Celsius.

A key factor in its spread is excessive soil moisture during the first half of the growing season, which facilitates spore germination and the invasion of the plant's root system and seedlings.

Heavy soils that are prone to crusting and waterlogging create a favorable environment for the accumulation and activation of Thecaphora deformans spores.

Disruption of crop rotation, where legumes are grown on the same field too frequently, leads to an accumulation of a high inoculum density in the soil layer.

Root system damage caused by pests or agricultural practices provides additional entry points for the pathogen's mycelium to penetrate plant tissues.

The primary economic impact of the disease is the total loss of yield in affected plants. Since seeds are replaced by spore masses, their commercial value becomes zero.

Beyond direct yield loss, there is a significant decrease in seed quality. Contaminated seeds that pass through a combine harvester can contaminate the entire healthy batch with spores.

Infected soil becomes unsuitable for growing legume crops for an extended period. This requires a change in the farm's crop rotation plan and avoiding susceptible species.

Economic damage includes the costs of cleaning seeds, the loss of harvest, and the necessity of implementing expensive protective measures on the field.

The spread of infection through seeds contributes to the introduction of the pathogen into new areas, making it a dangerous quarantine pest for many agricultural regions.

The foundation of management is the use of certified, disease-free seed material. Pre-sowing phytopathological testing of seeds helps prevent the introduction of the disease to fields.

Strict adherence to a crop rotation system, ensuring a break of 4–5 years before planting legumes on the same field again, is a critical method for reducing soil inoculum.

The application of fungicide seed treatments allows for the elimination of spores on the surface of the seeds and protects seedlings during the initial stages of growth.

• Deep plowing to bury spores to a greater soil depth.
• Timely removal of volunteer legume plants.
• Using resistant varieties and hybrids.
• Maintaining spatial isolation of fields from previous-year plantings.

If infection patches are discovered in a field, phytosanitary roguing must be performed—removing and destroying diseased plants before the pods crack and release spores.