Prevention and control of smut of Coix barley filled with black powder in ovary

With the extension of planting time and the expansion of planting scale, the occurrence of coix seed smut became more and more serious, affecting the yield and quality of coix seed. According to the occurrence law of coix seed smut, a set of effective comprehensive control measures of coix seed smut was introduced for reference.

barley smut

First, damage symptoms: Smut mainly damage the seeds of Job's tears, but also damage the leaves and buds. The seedling stage generally does not show symptoms, when the coix seed grows to 8-9 leaves and begins to enter the young panicle differentiation stage, the leaves begin to show symptoms, and a single or a string of purple-red tubercle protrusions are formed on the leaves or leaf sheaths of the upper 2-3 tender leaves, and then turn reddish brown, dry, and black powder can be seen when peeled off. Ovary infected, the affected ovary expanded into oval or nearly round, partly hidden in leaf sheath, initially purple, then gradually black brown, filled with black powder inside, surrounded by ovary, infected coix seed main stem and tiller stem every growth point became black powdery blister, most of the diseased plants could not bear fruit and formed gall.

2. Pathogenic bacteria: Coix seed smut is caused by infection of Basidiomycetes subphylum Coix seed smut. teliospores ovoid to elliptic or irregular, yellow-brown, densely spinulose or tuberculate. The teliospores are scattered and germinate to produce septate primary hyphae, basidiospores are produced terminally or laterally from one spore of primary hyphae, and secondary basidiospores are produced by basidiospores germination.

3. Characteristics of occurrence: Smut pathogen attaches to the seed of Job's tears or overwinters in soil as tetraspore. From April to May of the next year, when the temperature reaches 20℃ or above, the spore germinates and first infects the bud of Job's tears. In late July, the pathogen rose to the ear with the growth of the growing point of coix seed, causing the black ear to be infected by the pathogen at heading stage. When the black blister on the black ear cracked, it released black brown basidiospores, causing repeated infection or falling into the soil, causing the disease in the next year. The disease only harm Job's tears, not harm corn, sorghum and other gramineous crops.

IV. Causes of disease:

1. Seeds are infected. Fungus seeds are the primary cause of coix seed smut. The survey found that the farmers had a weak concept of keeping seeds of healthy plants and collected seeds casually, which led to high seed carrier rate and became the main source of disease in the next year.

2. Irrational farming system. Large area planting in successive years created favorable external conditions for infection cycle of coix seed smut. After the harvest of coix seed, many coix seed growers failed to dry the fields in time, collected, dried and burned the withered and residual stalks and leaves abandoned in the fields, providing a large number of bacteria sources for diseases in the next year. Due to the limitation of mountain conditions, most growers can only use traditional hoe and shovel to cultivate, which is not easy to deeply plow the field, and the field bacteria source has not been effectively buried. In order to pursue yield, factors such as high planting density and partial application of nitrogen fertilizer also promote the expansion and spread of pathogens. According to the characteristics of coix seed smut, prevention should be given priority, but some growers do not pay attention to seed and soil disinfection until the disease occurs, spraying chemicals to control, control effect is poor, and can not achieve the purpose of control.

V. Prevention and control technologies:

1. Clean up the garden thoroughly in time. After winter, dry the field, collect the residues of diseased plants and withered leaves, burn them together, turn over the soil in winter, and remove weeds at the edge of the field to reduce the amount of overwintering bacteria in the field.

2. Disinfection of seeds and soil. Healthy plants should be reserved to reduce the amount of bacteria in seeds. After many years of experiments and demonstration, before sowing, 70% thiophanate-methyl WP or 50% carbendazim WP can be used to dress seeds according to 0.5% of seed quantity, and the control effect can reach 100%. 500 times solution of 50% carbendazim WP or 500 times solution of 75% chlorothalonil WP can be used for soil disinfection.

3. Strengthen field management and apply phosphorus and potassium fertilizer reasonably. Avoid planting in the same field year after year. Reasonable planting density, reduce field humidity, reduce bacterial infection. Apply enough base fertilizer, do not apply fertilizer with gall, nitrogen, phosphorus and potassium fertilizer should be reasonably matched, appropriate potassium fertilizer should be added to improve the disease resistance of coix seed. After entering the heading period, coix seed should be inspected in time, and if diseased plants are found, they should be removed in time and burned intensively.