The pathogen of millet rust is Uromyces setariae-italicae, belonging to the genus Basidiomycotina. It occurs in all millet production areas, especially in Henan, Shandong, Hebei, and Liaoning. In recent years, it has picked up in Chaoyang, Chengde, Quzhou, Anyang and other places, and has been severely localized. In the year of the rust disease, the general reduction in production is more than 30%, and serious plots or even granules are not received.
1. Disease characteristics
Millet rust can harm leaves and leaf sheaths but occurs more severely on the leaves. At the onset of the disease, red-brown uredia spores are produced on both sides of the leaves, especially on the back. The summer spores are slightly raised, round or elliptical, about 1 mm, break through the epidermis after exposure to maturity, and the surrounding epidermis gives off yellow-brown powder, namely the summer spores. In severe cases, the summer spores are covered with leaves, causing the leaves to die, the stems to be soft, the grains are thin, and the weather is prone to lodging, and even result in an outbreak. The uredia spores of disease-resistant cultivars are small, with dead or chlorotic surrounding host tissues, or only minor lesions. The uredia spores cannot spread beyond the epidermis. According to records, in the late onset of the disease, there are also scattered black and white round or oblong ecchymosis on the leaves, namely the teliospores heap, but it is rare in the north. In India, cynospores germinate to produce spore-forming invading spores and rust spores of Cordia rofsii, and spores re-infest the millet to complete the entire invasion period. No ragwood was found in northern China, and the entire disease infestation cycle was completed with the summer spores. Millet rust is an obligate parasite and has a high degree of pathogenic differentiation. There are different physiological races in different regions.
2. The law of occurrence
Millet rust is an epidemic disease, which occurs mainly in the late growth stage of millet, and usually begins before and after the heading of millet. With the summer spores with cereals, fertilizers in dry places, or overwintering with the sick body in the field, it became the source of infestation early in the year. The summer spores splashed on the leaves in the event of rain. They invaded through the stomata after germination and grew under the epidermis or in the intercellular space. The uredia spores were generated after about 10 days. After the summer spores mature, a large number of summer spores are released and reinfestation is formed through wind and rain. If the climatic conditions are appropriate, the onset center will soon form and spread to all fields, causing an outbreak of the disease. The epidemic process can generally be divided into three periods: the onset of the onset center—the rate of diseased leaves gradually increases at the onset of the disease, the severity does not develop, and a clear onset center forms in the field; the prevalence rate extends from the onset center to the whole field. Expansion, widespread disease throughout the field, diseased plant rate, diseased leaf rate increased sharply, provided sufficient bacteria source for field epidemic; severity increase period - diseased plant rate, diseased leaf rate reached a peak, incidence increased sharply, causing plant lodging , seriously affecting production. In northern China from late July to mid-September is the main epidemic of millet rust. High temperature and rain are conducive to disease. The precipitation in July-August is the key factor in determining the prevalence of rust in the year, with more rainfall, more severe disease, and lesser incidence in drought years. Excessive use of low-lying land and nitrogen fertilizer, the density of the field is too heavy. There is a significant difference in disease resistance among millet varieties. In addition to damaging millet, millet rust can also infect green green foxtail and glutinous rice.
3. Investigation points
After the jointing of millet, attention should be paid to the investigation of the presence or absence of rust spores on the leaves of the millet, and timely prevention and treatment should be conducted in the center of the disease.
4. Control technology
(1) Planting resistance (resistant) varieties: Disease resistant varieties are the most economical and effective measures to prevent and control the disease. In the re-emerging areas, resistant varieties are selected, such as Fuchuang 1, Yugu 11, Chaogu 13, 201019, etc. .
(2) Agricultural control: Strengthen field management, ensure close planting, timely drainage in field during rainy season, reduce nitrogen fertilizer, increase phosphorus and potassium fertilizer, and increase plant resistance to disease.
(3) Chemical control: When the diseased leaf rate in the field is 1%-5%, spray with 20% triadimefon EC 1000-1500 times, or 12.5% ​​diniconazole wettable powder 1500-2000 times, interval 7-10 days Prevent once more.
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