At present, corn has developed into a bell-mouth period, which is the coexistence period of reproductive growth and vegetative growth, and thus is a weak period against disease infestation. According to investigation and monitoring and peasant households consultation in various areas, corn disease in our province has entered its peak period, and mid-stage pests have also begun to harm. Some diseases and pests are more serious, and pests in the middle and later stages of corn should be quickly controlled.
First, the occurrence and trend analysis
1. Climatic conditions. Since May, precipitation in our province has been frequent and the rainfall is heavy. For example, on July 15th, Yucheng rained 60 mm. Only last week, the average precipitation in the province was 60 mm, which was 96% higher than the average. Among them, Tangshan, Qinhuangdao, Baoding, Shijiazhuang, Xingtai, Hengshui, and Tancheng were 1~1.8 times more than those in normal years, and soil moisture content in most areas had reached or nearly reached saturation. The temperature is lower than in previous years. In the coming week, the province will still be rainy. It is forecast that there will be rainy weather on the next day, and it will enter the volcano on July 19, and the weather will be hot and humid. This climate is very suitable for the occurrence of high-humidity diseases and insect pests.
2. The occurrence of pests and diseases. The current pests and diseases that have occurred in corn include corn borer, cotton bollworm, different leafhopper, brown leaf spot, curvularia leaf spot, spot leaf spot, and bacterial stalk rot. Disease is more important than insects. Disease occurred earlier than in recent years. The big bell-mouth period is the susceptible stage of corn brown spot, which is currently widespread. The incidence of the disease is significantly different between the varieties. The occurrence of the disease is heavy in Dandan 20, followed by Zhengdan 958. Guantao County began to see the diseased plant on July 11. In Renqiu City, the incidence was heavier, the rate of sick fields was 40%, the diseased plant rate was 2% to 10%, and the highest rate was 25%. In early July, the province began to see large-scale spot disease, heading to the filling stage for the susceptible period of corn, so it is currently the initial stage. Lucheng County investigated on July 18, and 60,000 mu of small spot disease occurred. Curvularia spp. occurs in Hengshui. Jingxian County has a 30% disease incidence rate and Wuqiang 40%. Incidence was also mainly in Dandan 20 and Zhengdan 958. On July 19th, farmers in Gucheng County consulted. Corn was rotted and rotted in more than 30 centimeters from the ground. It had fishy odor and bacterial stalk rot occurred. Guantao County surveyed 50,000 mu of sheath blight in early July.
3. Trend analysis. July-August is the same season as rain and heat, especially this year's weather conditions are particularly conducive to disease epidemics. The onset condition of the leaf spot is temperature 26°C-32°C. Under high humidity conditions, the field density is too large and it is easy to be diseased. The bacteria propagate on the foliage and re-infestation by wind and rain. Low-lying land is not susceptible to infection. The suitable temperature of the pathogen is 20°C～28°C. When the relative humidity of the air is more than 90%, it will facilitate the breeding of pathogens. Relative humidity less than 60%, the disease is inhibited. From jointing to heading, corn is susceptible to continuous rain. Curvularia spp. In the high-temperature season from July to August, there are 4 to 5 days of rain, and the disease may become popular. The suitable temperature for corn brown spot disease is 23°C～30°C, and the rainy weather during the middle and late stages of corn growth is more prone to the epidemic under high humidity and high temperature conditions. In the years after the jointing of rain, there was heavy occurrence of sheath blight. Bacterial stem rot occurred in the small trumpet period of corn. The average temperature of 30 °C, relative humidity of more than 70%, damp and hot weather conducive to disease. Therefore, the occurrence of these diseases has aggravated.
In terms of potential diseases, the head smut of the corn head shows signs of disease, and the southern rust can occur under 100% high humidity conditions. Rainwater is poured into the bell mouth, which is hampered by Thrips and Swedish fly. It may cause top corn to decay. After the rain, it is easy to cause fungal stem rot. According to tests, Rhizoctonia solani was active in the middle and late Shijiazhuang area in recent years, causing root rot.
In terms of pests, the weather is suitable for corn borers. The suitable temperature for corn borer is 19-24°C and the relative humidity is above 60%. Especially when spawning, high relative humidity is required, relative humidity is lower than 25%, and adults do not lay eggs or spawn very little. Above 40%, the amount of eggs laid increases. The largest amount of eggs was laid at over 80%. When the temperature is 25°C and the relative humidity is 90%, the eggs can all hatch. Relative humidity is below 90%, and the survival rate of young larvae is low.
In the later period, the moths and stickworms will also occur, and the overall occurrence is lighter. However, local mini-environmental armyworms may concentrate spawning hazards. High-humidity conditions should also pay attention to snails and cockroaches (currently localized hazards).
Second, prevention strategies and methods
1. Take care of everything. During the trumpet period, there are young corn borers, armyworms, and cotton bollworms that are harmful to the heart and leaves, as well as thrips and Swedish flies, and need to be controlled. At the time of heading, there were corn borers, stick insects, cotton bollworms, and thrips on the filaments and tender sticks, or tapeworms on the tassels. The lower part of the corn includes roots, which cause sheath blight and root rot. Both the upper and lower parts need to be investigated, and phoxim granules are sprayed into the heart and leaves, or 1500 times sprayed with Le Siben EC to prevent and control various pests. To prevent corn rot, pour medicine into the bell mouth and pharmacy formula: 10% imidacloprid 1000 times or 5% acetamiprid 1500 times plus agricultural streptomycin 500-800 times to pour into the heart, every 5 days, use two Times. For the sheath blight strains that have clouded spots on the stalks or leaf spots on the leaves, the 50% carbendazim 500 times solution can be sprayed onto the stem base. If the plants are dwarfed, yellow leaves, and roots rot, apply carbendazim 500 times solution or 85% trichloroisocyanuric acid 1500 times to irrigate the roots. Once in 7 days, use 2 to 3 times.
2. Leaf and stem balance. In the middle and late stages, various leaf spot diseases are endemic, and yellow spots with nearly rectangular shape are formed on the leaf surface. The large spot is a large spot disease. The small round or oval side of the spot has a yellow halo. Mycorrhizal leaf spot, and the deep vein purple spot on the main vein of the leaf is brown spot. Size spot and brown spot were treated with carbendazim or chlorpromazine spray, and brown spot was also available with 20% triadimefon EC 3000 times, or 12.5% ​​diniconazole powder 30 g, 30 kg water; Curvularia leaf spot 200 times faster sickle or 1000 times Tepotazole. These disease prevention and treatment agents can also be added with spraying fertilizer, overdose or potassium dihydrogen phosphate and other foliar fertilizers to promote the recovery of corn growth, improve resistance to disease, medication once every 7 days, continuous medication 2 or 3 times. At the same time, pay attention to whether stem stem rot and stem rot occur in the stem, and it should be sprayed for prevention. The medicament can be used as a 3000 times solution of 85% trichloroisocyanuric acid and used once every 7 days.
3. Diseases and insects take into account. Diseases and insect pests are mixed on the same plant in the later stages, mainly Lepidoptera, Coleoptera, etc. Smut, leaf spot, and rust may also occur. Drug selection and application should consider one drug and multiple effects, one spray and more defense. Such as spray insecticide mixed broad-spectrum fungicide (such as diniconazole, carbendazim). Head smut does not need to be sprayed, but it is only necessary to remove the black bag (male, tassel) for deep processing.
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