What are the causes and control methods of gray leaf spot of corn, apple, red bayberry, cowpea and soybean?

Grey spot, also known as brown spot, spot or frog eye disease, is a worldwide disease, so what are the causes and control methods of gray spot of corn, apple, red bayberry, cowpea and soybean? Let's learn more about it.

1. Corn gray leaf spot

1. For corn planted in the first and middle of May, the disease of corn gray leaf spot generally begins in mid-late July, starts from foot leaves, develops slowly in July, harms the middle leaves, gradually aggravates the disease in August, breaks out rapidly, and reaches the peak in mid-late September, forming the so-called "autumn wind disease". In general, the diseased leaf rate of corn gray leaf spot is 99%, and the disease index is more than 30; in heavy fields, the diseased leaf rate of corn gray leaf spot is 99%, and the disease index is more than 90, which leads to the death of the whole corn plant in a short time. The disease was prevalent in the "S" curve during the growth period of maize.

two。 Chemical control methods: at the initial stage of the current disease, choose 10% difenoconazole granule 1500 times solution (40 grams per mu with water 60 kg), or choose 15% trimethoprim wettable powder solution (100 grams with water 60 kg per mu), or select 30% hexazolol suspension (20g/ mu, 45 kg water), control once every 10 days, a total of 3 times. In the areas where the disease is more serious, 15% vermicellin wettable powder can be used to mix seeds according to 0.12% seed weight to reduce the disease.

2. Grey spot of apple

1. There are two kinds of pathogens causing apple gray spot disease: Phytophthora pear and Alternaria alternata. When the environmental conditions are suitable in spring, conidia spread with wind and rain. The disease began in the middle and last ten days of May in the northern fruit area, and the peak period was from July to August. Generally, the disease occurs more frequently in autumn, and the harm is also more serious. The occurrence and prevalence of the disease are closely related to climate and variety. The onset of disease is early and severe in years with high temperature, high humidity and heavy rainfall. Guoguang varieties are susceptible to disease.

two。 Control methods: disease-resistant varieties should be selected in areas with serious disease. The occurrence of gray leaf spot is mostly in autumn, so we should focus on the prevention and control in the later stage. Before the onset of the disease, the following agents can be used: (1) 200 times Bordeaux solution; 200 times zinc-copper lime solution (zinc sulfate 0.5: copper sulfate 0.5: lime 2: water 200); 30% basic copper sulfate suspension 300-500 times; 70% mancozeb wettable powder 500-600 times.

3. Grey spot of Myrica rubra

1. The pathogen is caused by fungi of subphylum ascomycetes, Cystis, Coleoptera, Cysticercaceae.

two。 Prevention and control methods: (1) cut off dead branches and leaves in spring to reduce the source of infection of the disease.

(2) the newly planted bayberry should choose the mountainous area with good drainage and sufficient light as far as possible, and pay attention to the application of organic fertilizer and potash fertilizer in cultivation and management.

(3) Chemical protection and prevention. According to the experiments of the former Zhejiang Agricultural University and the Zhejiang Academy of Agricultural Sciences, it was considered that the former should be sprayed once in late May and once after harvest, the former with Bordeaux solution of 1 and 200, and the latter with an 800-fold solution of 70% methyl topiramate wettable powder.

4. Grey leaf spot of soybean

1. The pathogen overwintered on the diseased remains or seeds with mycelium or conidia and became the source of infection at the beginning of the next year.

two。 Control methods: (1) resistant varieties Ludou 10, Suinong 8, Hefeng 25, 27, 28, 29, 30 in Heilongjiang, and Hefeng 34 physiological races 1, 2, 3, 4, 7, 8, 9 and 10 were selected. However, the resistance of varieties is very unstable, so we should pay close attention to the virulence changes of bacteria and replace new disease-resistant varieties in time.

(2) reasonable rotation of agricultural control should be advocated to avoid continuous cropping and turn deeply in time after harvest.

(3) spraying to control leaf or grain diseases, at the peak podding stage, 36% carbendazim suspension or 40% chlorothalonil suspension (Shuntianxing 1) was sprayed by aircraft (Beijing Shunyi County Pesticide Factory), 50% thiophanate wettable powder 600 times 700 times, 50% carbendazim wettable powder 1500 times, 65% carbendazim 1000 times, 50% carbendazim 800 times. Once every 10 days or so, prevent and cure once or twice.

5. Cowpea gray spot

1. The conidia or mycelium overwintered on the diseased residue in the soil, and the hyphae or spores could survive on the diseased residue for half a year.

two。 Prevention and treatment methods: (1) thoroughly remove the residual body and reduce the source of primary infection.

(2) 2-3-year rotation with non-legume crops.

(3) using disease-resistant varieties.

(4) do a good job in the management of temperature and humidity, pay attention to dehumidification and improve the performance of ventilation.

(5) at the initial stage of the disease, 50% carbendazim wettable powder or 75% chlorothalonil wettable powder or 50% carbendazim wettable powder 1500 times were sprayed.