Coix smut

The disease is caused by the basidiomycete fungus Ustilago coicis, which is a specific pathogen targeting Coix lacryma-jobi, commonly known as Job's tears. This fungus is highly adapted to its host and causes significant physiological shifts in the plant's reproductive system.

Symptoms of the infection manifest primarily in the inflorescences. Instead of developing normal grains, the infected plants produce galls or swellings within the floral structures. These galls are filled with a dark, powdery mass of teliospores, which rupture to release fungal spores into the environment.

Development and spread of the disease are heavily influenced by environmental conditions, particularly moisture levels during the anthesis stage. High humidity and mild temperatures provide the optimal environment for spore germination and infection of the host's reproductive organs via the stigma.

The economic impact of Ustilago coicis is substantial due to complete reproductive failure of the host. Because the pathogen colonizes the ovaries, the plants become sterile, leading to a total loss of seed yield. This can be devastating for producers relying on high-quality grains for food processing or pharmaceutical use.

Management strategies focus on breaking the infection cycle. Prevention is the most effective approach, including the use of certified disease-free seeds and chemical seed treatments. Furthermore, implementing proper crop rotation practices helps to reduce the inoculum load in the soil, preventing the disease from re-establishing in subsequent seasons.