Symptoms mainly harm the flower. The yellow honey dew-like mucus is produced first, and then the flower part inside the clam shell expands, forming a purple-black, long-angled sclerotia, called ergot. Only a few spikelets on a wheat ear are affected, and one to several ergots grow. The adjacent florets are often infertile. Ergot differs in size depending on the type of host wheat. Rye rye diameter 0.5cm, about 1-3cm. The ergot is a precious Chinese herbal medicine. Ergot is poisonous. The 5% ergot in the seeds is inedible and cannot be used as feed.
The pathogenic Claviceps purpurea (Fr.) Tul. is called ergot fungus and belongs to Ascomycete spp. Sclerotia harder, purple black, internal white. The ascospora shell is born in the subhead of the sclerotia that grows and sprouts, and the subseat head is nearly spherical. Ascospore shell lavender, bottle-shaped, with holes. The ascus is colorless, barrel-shaped, with a size of 12-303 (μm) and 8 ascospores. Ascospores are colorless and filiform and are 50-76μm in size. The conidia unit cells are colorless, ovoid, and are 0.7-3.5 μm in size. There are different specializations of ergot. Some can infect rye, but also can infect barley, wheat, etc. Some can only infest rye, but do not infect barley.
Transmission routes and conditions Sclerotium falls into the soil for winter. In the spring of the following year, the soil is sprouted to generate red seats and sub-handles, and endogenous ascospores are formed. When the wheat crops bloom, the ascospores are transmitted to the florets by wind and rain, mixed insects, and produce honey dew-like mucus for about 7 days. There are a lot of conidia in the mucus, which can be spread by insects, raindrops, etc. The nucleus is formed in about 15 days and the ovary becomes ergot. After the sclerotia had matured, it fell into the soil and became a source of infestation in the second year. The long flowering period of the wheat crops and the large opening of the outer cultivars are serious. Rainy and moist conditions during the flowering period are beneficial to the disease. The moist soil in spring is beneficial to the germination of sclerotia. The order of ergot prone to occur in wheat crops is: rye> triticale> barley> durum wheat> common wheat> oats.
Control methods (1) Use disease-free (ergosterol) seeds. If sclerotia are mixed in the wheat seed, 20% - 30% saline solution can be used. (2) Deeply turn over the wheat field so that the sclerotia cannot germinate. (3) Rotation with non-grass crops. Clear wild hosts inside and outside the wheat field.
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