This year's rain is relatively large compared with previous years, and the air humidity is large, which creates favorable conditions for the occurrence of large and small spots in corn, round spots, eye spots, gray spots, and brown spot disease. This type is a common disease in the growth process of corn, after the plant feels diseased, often the same leaf can be mixed with various spots, or multiple spots are contiguous with each other, in severe cases, the leaves are dry, chlorophyll is reduced, photosynthesis decreases, affecting the subgrain grouting caused by yield reduction. Such diseases can generally cause yield reductions of 15 to 20%, and in severe cases, they can reach more than 50%, and the impact on corn yields is very serious. Therefore, it is hoped that the majority of growers will pay attention to such diseases and minimize losses if they are found to be prevented and controlled in a timely manner.
01 Corn spot disease
Maize small spot disease (Bipolaris maydis) is a common leaf disease in corn areas around the world, China's summer corn area disease is more serious than spring corn, pandemic years can cause greater losses.
Symptoms: Corn can cause great losses from seedling to adult stage. Take the onset of male extraction and grouting period. The spots are mainly concentrated on the leaves, generally starting from the lower leaves and gradually spreading upwards. The spots are initially water-soaked, then turn yellowish-brown or reddish-brown, with darker edges. The spots are oval, nearly circular or oblong in size, 10 to 15 mm to 3 to 4 mm in size, and sometimes 2 to 3 concentric chakras are visible on the spots.
Pathogenesis: the pathogen overwinters in the disease residue with hyphae or conidia, and produces a large number of conidia in May and June when the temperature is more suitable in the following year, which is spread by air flow or rain. The conidia on the remnants of the field disease left over after the harvest of spring maize can continue to spread to the summer maize field, so in the mixed spring and summer maize areas, the summer maize is always more severe than the spring maize. In North China, the temperature of 25 °C or more in July and August is the most suitable for the epidemic of the disease, during which if there is a lot of rain, a lot of rain, and a large temperature, small spot disease will occur seriously.
Prevention and control methods: (1) Promote the planting of disease-resistant and high-yield varieties, which can effectively reduce the occurrence of small spot diseases. (2) Strengthen cultivation management, and apply compound fertilizer in the jointing and ear extraction stages to promote robust growth and improve plant disease resistance. (3) Clean the countryside, burn the disease residue in a concentrated manner, and reduce the source of disease. (4) Pharmaceutical prevention and treatment, at the beginning of the disease, use 50% carbendazim wettable powder 500 times liquid, or 65% daisen manganese zinc wettable powder 500 times liquid, or 70% methyl tolbuzin wettable powder 500 times liquid, or 75% bacillus Qing wettable powder 800 times liquid, or agricultural resistance 120 water agent 100 ~ 120 times liquid spray. From the end of the heart leaf to the extraction of males, spray once every 7 days, 2 to 3 times continuously.
02 Corn large spot disease
Maize large spot disease occurs in all maize-producing areas, and the incidence is more severe in lower temperature areas such as northeast, northern and northwestern China, and mountainous areas in the south. In the year of large occurrence, the production of susceptible varieties was reduced by about 50%.
Symptoms: Harmful to leaves, in severe cases affecting leaf sheaths and leaf cladding. Field onset begins in the lower leaves and gradually progresses upwards. At the beginning of the disease, it is a water-stained blue-gray dot, and then develops along the leaf veins to both sides, forming a central yellow-brown, dark brown fusiform or spindle-shaped large spot, when the humidity is high, the lesion heals into a large piece, the spot produces gray-black mold, the disease is not longitudinal cracked or wilted, the fruit spike is infected with leaves, and the spots are irregular.
Pathogenesis: The pathogen overwinters inside and outside the diseased remnants as mycelium or conidia. The source of the first impregnation of field-borne disease is mainly from the conidia regenerated by overwintering tissue on corn stalks, which are transmitted by wind and rain. The temperature suitable for the onset of the disease is 20 ~ 25 ° C, and more than 28 ° C has an inhibitory effect on the disease. Most of the temperatures in northern China from June to August are in the appropriate temperature range for the onset of the disease, so the number of rainy days and rainfall in these three months are the determinants of the severity of the disease. However, in years when the field spots appear later, regardless of the later climatic winter conditions, the occurrence of large spots will not be too severe.
Prevention and control methods: (1) Promote the planting of disease-resistant varieties. (2) Remove the disease residue in the field, burn it in a concentrated manner, or deep plough and deep ploughing, and bury the pathogen. (3) Strengthen field management, promote the healthy growth of corn, and enhance disease resistance. (4) Chemical control, with 50% carbendazim wettable powder 500 times liquid, or 50% dented special wettable powder 800 times liquid, or 80% Daisen manganese zinc wettable powder 500 times liquid, or 75% Bacillus Qing wettable powder 500 ~ 800 times liquid, spray 1 to 2 times in the male flowering stage of corn, spray once every 10 to 15 days.
03 Round spot disease
Corn round spot disease is a devastating disease in corn production, which occurs in Shaanxi, Hebei, Heilongjiang and other regions in China. The disease seriously endangers the healthy growth of corn and causes great economic losses to farmers.
Symptoms: The disease can impregnate leaves, ears, bracts, and leaf sheaths. The lesions on the leaves are initially water-stained pale green to pale yellow dots, and later expand into round or oval spots, with concentric chakras, central light brown, brown edges, with a yellow-green halo, and a size of 1 to 2 mm to 3 to 10 mm. Several spots confluence to form long stripes. The inward expansion of the spots on the bracts can invade the corn grain and panicle axis, the diseased part becomes black, the fruit panicle becomes curved, the heavy grain and panicle axis become black, and the grain and bracts are covered with black mold layers.
Pathogenesis: The infection cycle of corn spotted bacteria is very similar to that of corn spotted bacteria. Pathogenic bacteria overwinter on diseased leaves, leaf sheaths, bracts, and fruit spikes as mycelium, becoming the source of initial infection the following year. The pathogen first senses disease on the leaves, and after the ear is ejected, it is first infected on the bracts and leaf sheaths of the ear. After initial infestation, the spots on the leaves and bracts produce a large number of conidia, which are reinfected with the help of wind, rain and human transmission. The incubation period is 1 to 2 days. This disease can occur at both the seedling stage and the adult stage, but most of them start from the flared mouth stage to the male stage, and the filling stage to the milk ripening stage is the peak stage. If disease-resistant varieties are planted, the disease has little impact on corn yield, generally reducing production by less than 5%, but planting disease-susceptible varieties in large areas for many years will aggravate the occurrence of diseases, or even eliminate production.
The occurrence and prevalence of maize round spot disease mainly depends on temperature and moisture conditions. The disease is mild at the seedling stage, and the rainy season enters in late July, and the high temperature and high humidity are favorable conditions for the onset of circular spot disease. According to the survey, when the relative humidity in the field reaches more than 85%, when the temperature is at 25 °C, the pathogen is transmitted by the wind, and after 5 to 7 days, the leaves and bracts of the plant will be affected by a large number of diseases, resulting in a large number of disease spots. In dry years, the incidence is milder. The disease resistance varies greatly among maize cultivars. According to the survey, the incidence of hybrid 1-generation seeds is less than that of the parents of the field, and the incidence of self-inbred mothers is higher than that of the father, and it is mainly harmful to the parts below the ear of fruit.
Control methods: planting disease-resistant varieties: planting disease-resistant varieties is the most economical and effective method for disease control, and the disease resistance to corn rotunda varies greatly among maize varieties. At present, there are no immune varieties of round spot disease, most of the maize varieties promoted are resistant to round spot disease, and the inbred lines and hybrids that are resistant to round spot disease are Erhuang, Tiedan No. 8, Ying 55, Liao 1311, Ji 69, Wu 105, Wu 206, Qi 31, YuBai, H84, 017, Jidan 107, Chundan 34, Rongyu 188, Chia Tai 2393 and Jinyu 608.
Cultivation and disease prevention: delay the seedlings, cultivate strong seedlings, timely and late sowing, miss the peak period of the disease; do a good job in pastoral hygiene, turn the land deep in winter, and use water and drought rotation in places where conditions are available; timely remove diseased leaves and reduce the source of re-infection bacteria; raise the ridge to reduce the humidity in the field; increase the application of phosphorus and potassium fertilizers, strengthen field management, and enhance the disease resistance of plants.
Pharmaceutical control: spray prevention of leaves with 15% triazolone wettable powder according to 0.3% of seed weight before sowing, spray prevention with 50% carbendazim wettable powder 500 to 600 times liquid or 70% daisen manganese zinc wettable powder 500 to 600 times liquid at the jointing stage, generally spray 1 to 2 times, spray once every interval of 7 to 10 days; in the peak period of corn spit (when more than 50% of the fruit spikes spit silk), use 25% powder rust rather wettable powder 500 to 600 times liquid, or 50% Carbendazim wettable powder 500 ~ 600 times liquid, or 70% daisen manganese zinc wettable powder 400 ~ 500 times liquid spray fruit spikes, continuous control 2 to 3 times, every interval 7 ~ 10 days spray once.
04 Corn gray spot disease
Cercospora zeaemaydis Tehon and Daniels, also known as tailspora leaf spot disease, is a new and very harmful disease that has occurred in the corn-producing areas of northern China in recent years. In severe illness, most of the leaves become yellow and scorched, the fruit panicle droops, the grain is loose and dry, and the weight of 100 grains decreases, which seriously affects the yield and quality.
Symptoms: The disease mainly occurs on the leaves, leaf sheaths and bracts of maize at the mature stage. At the beginning of the disease, the water-stained light brown spots gradually expand into light brown stripes or irregular gray to brown long stripes, which extend parallel to the leaf veins, the middle of the spots are gray, and the gray-black mold layer, that is, the conidia and conidia of the pathogen, can produce gray-black mold layers on both sides of the leaf (especially on the back) in the later stages of the disease spots, that is, the conidia stalks and conidia of the pathogen.
Pathogenesis: The pathogen overwinters on the residues such as corn stalks with mycelium and conidia, becoming the source of initial immersion in the second year, and the disease is more suitable for occurrence in warm, humid and foggy areas. The planting of disease-induced varieties in large areas for consecutive years is one of the important conditions for the occurrence of the disease. In North China and Liaoning Province, the disease began in early to mid-July and peaked from mid-August to early September.
Prevention and control methods: (1) After the corn harvest area, remove the residue of the disease such as corn straw in time to reduce the source of initial immersion in the field. (2) Promote the planting of disease-resistant varieties, at present, the backbone inbred lines of China's multi-application such as Huang Zhao 4, Ye 107, E28, Dan 340, 478, 5003, etc., as well as large-scale planting hybrids such as Ye Dan No. 2, Ye Dan No. 11, Shen Dan No. 7, Dan Yu 16, Tie Dan 10, etc. are more disease-resistant, while the newly bred Zheng Dan 14, Dan 408, Dan 3034, Shen Test 29 and Shen Test 30 are more resistant to disease, and the combination of disease-resistant parents such as Shen 137 and Dan Huang 19 is also more disease resistant. (3) Rational watering and fertilization to promote healthy growth and improve the disease resistance of corn. (4) After the flowering pollination of maize or the early stage of the disease, use 50% carbendazim wettable powder 500 times liquid, or 80% anthrax Fumei wettable powder 800 times liquid, or 50% castor special wettable powder 600 to 800 times liquid, spray prevention and control, 7 to 10 days after another application of 1 drug.
05 Maize brown spot disease
Regarding maize brown spot disease, it is enough to see this article
06 Corn eye spot disease
Corn disease | note that this is anthrax in the north, and this year the northeast is a bit serious
Summary: Timely prevention and control of corn leaves before the appearance of disease spots, timely spraying after the appearance of disease spots, and minimizing losses, you have done your part in national food security.