This disease can cause corn to reduce production by 10%-20%, seriously up to 40%!
Corn brown spot
Brown spot condition
The pathogen of corn brown spot disease is the juniper bacillus, and the pathogens are overwintered in the land or diseased bodies by dormant spores (sacs). In the second year, the bacteria are spread by airflow to the corn plants, and a large number of germinations are generated under suitable conditions. In zoospores, zoospores swim in water droplets on the surface of the leaves and form infested silk, which invades the tender tissue of the corn.
The bacteria prefer high temperature and high humidity, and the germination of the dormant sporangia requires water droplet conditions and a temperature of 23 to 30 °C. In July and August, if the temperature is high, the humidity is high, and the rainy days are more, it is conducive to the onset.
In the infertile soil, the leaves are yellow and the disease is serious; in the land with high soil fertility, the corn is strong, the leaves are dark green, and the disease is light or not. Generally, it is easy to cause disease when 8 to 10 leaves of corn are used, and the disease will not occur again after 12 leaves of corn.
Symptoms of brown spot
The disease mainly occurs on the leaves, sheaths and stems of corn, with the most lesions at the junction of leaves and sheaths.
First, at the tip of 4 to 8 leaf blades at the top, the lesion is initially round or elliptical to linear white or yellow spots, the leaves are faded to reddish yellow, and many small spots are usually joined together to form a transverse band. Large yellow spot;
The diseased tissue gradually turned brown or dark brown, and healed into large irregular plaques, which often caused vascular bundle necrosis, which caused the leaves to lose nutrients and died, which had a great impact on yield. This disease can cause corn to reduce production by 10%-20%, severely up to 40%.
Brown spot prevention and control technology
First, prevent early. Fields where brown spot disease occurred in the past, in the 4 to 5 leaf stage of corn, the use of triazolone or tebuconazole to control the fungal agent foliar spray can prevent the occurrence of corn brown spot.
Second, timely prevention and treatment. Immediately after the onset of corn, the fungal agent is sprayed with triazolone or tebuconazole. According to the current rainy climate characteristics, the spray sterilization agent should be 2 to 3 times, with an interval of about 7 days. Within 6 hours after the spray, the following rain should be sprayed after the rain. It can also be controlled by 12.5% ​​straw or 12.5% ​​rusting leaf spray.
Third, timely topdressing. At the same time of active prevention and control, timely application of quick-acting nitrogen fertilizer such as urea or spraying of foliar fertilizer such as fulvic acid on the diseased field or weak field will promote corn growth and reduce disease losses.
Guidelines for the use of major pests and diseases at the ear stage
The main pests and diseases at the ear of corn include corn brown spot, stem-based rot, tumor smut, sheath blight, size spot, corn borer, armyworm, cotton bollworm, corn borer and so on. Attention should be paid to field investigations, timely prevention and control, control of pests and diseases, and reduction of losses.
The end of heart leaf is also called the big bell mouth period. It is a key period for controlling corn borer and cotton bollworm. It can be applied with granules, and the control effect is good. 5% octyl sulfide can be used. Triazophos granules 150--250 g/mu, 10% diazinon granules 400--600 g/mu, 1.5% phoxim granules 500--750 g/mu, 5% thiocarbamate Granules 2 - 3 kg / acre, mixed with fine soil 15-20 kg, evenly lost heart.
From the heart leaf stage to the tassel stage of corn, in the larvae of corn borer and cotton bollworm at the age of 2-3, it can also be sprayed with the following agents: 1.8% avermectin EC 20--40 ml/mu, 20% xin Sulphur-phosphorus EC 200-250 ml / mu, 48% chlorpyrifos EC 70--90 ml / mu, etc., 40--50 kg even spray control with water.
This period is a key period for the prevention and control of corn sheath blight. The disease is promptly applied in the field. Combined with the control of other diseases, the following agents can be sprayed: 40% carbendazim suspension 80-100 ml/mu, 5% Jinggangmycin water 100-150 ml / mu, 23% thifluzil suspension 14--25 ml / acre, 30% difenoconazole emulsifiable oil 15--30 ml / acre, 50 kg evenly sprayed with water, interval 7- - Spray once every 10 days, even spray 2 - 3 times.
In this period, corn spot disease, small spot disease, brown spot disease, rust, stem-based rot, and tumor black powder disease have begun to have different degrees of disease, and prevention and prevention should be taken.
The following bactericides can be used: 50% thiophanate-methyl WP 500--800 times solution, 50% carbendazim WP 500-600 times solution, 25% benomyl emulsifiable concentrate 800 times solution, 12.5% Xylazole alcohol wettable powder 1000--1500 times liquid, 50% procymidone wettable powder 1000--1200 times liquid.
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