What is the black stuff growing on corn

Corn is one of China's important food crops, grown all over the country. As a cash crop, growers may have encountered tumor-like growths about 4-14 cm on corn. At first they are white, and later they turn gray or white. When broken open, a large amount of black powder comes out. So, what is the black stuff growing on corn?

1. What is the black stuff growing on corn?

The black stuff growing on corn is a pathogen called corn smut fungus. The smut fungus can infect every organ from seedling to mature plant. Any aboveground young tissue with meristematic capacity can be infected and develop tumor-like growths of different sizes and shapes. The tumors are initially white or light purple, gradually turn gray, and after rupturing release a large amount of black powder.

2. What is the disease pattern of corn smut fungus?

The pathogen of corn smut fungus is a fungus (basidiomycete), and the black powder inside the galls is the teliospore of the pathogen. The teliospores overwinter in the soil, on the soil surface, on diseased residues, and in soil mixed with manure.

The overwintered teliospores become the primary infection source for the disease the following year. Under suitable conditions, they germinate to produce basidiospores and secondary basidiospores, which spread with wind, rain, and airflow to young meristematic tissues such as corn leaves, nodes, axillary nodes, and tassels and ears, grow and spread within the tissues, and produce a substance similar to auxin that stimulates vigorous division of cells in the host's local tissues, gradually swelling to form galls. When the galls mature and rupture, they release black powder (teliospores) for reinfection.

The teliospores have no dormancy period and can carry out multiple reinfections during the corn growing period. They spread rapidly during the tasseling and flowering stage of corn, forming a peak incidence period, and stop infecting until the corn matures.

3. What pesticide is used for corn smut fungus?

Before corn emerges, spray a herbicide with bactericidal effect on the soil surface. You can use 15% triadimefon for seed dressing at a dosage of 0.4% of the seed amount; when corn is about to tassel, spray with 1% Bordeaux mixture, which has a certain protective effect;; about 10 days before corn tasseling, spray with 50% thiram wettable powder at 500-800 times dilution, which can reduce reinfection of smut disease.