Occurrence and control techniques of soybean anthracnose

1 symptoms of disease

Most of the diseased seeds died in the soil before emergence and could occur from seedling stage to mature stage. The pathogen could invade young stems from cotyledons, harming stems and pods, as well as leaves or petioles.

1.1 Cotyledon disease symptoms can occur from seedling stage to mature stage, there are dark brown disease spots on the emergence cotyledons, the edge is slightly light, the disease spot expansion often appears cracking or depression, when the climate is humid, the cotyledons become water-immersed, wilt and fall off quickly.

1.2 the symptom of leaf disease is infected on the leaf, the spot is irregularly shaped, the edge is dark brown, the interior is light brown, and the spot is rough, spiny black spot, which is the conidium of the pathogen.

1.3 symptoms of stem disease primary reddish brown spot, gradually brown, and finally gray, irregular shape, upper densely spiny black spots, often encircling the whole stem.

1.4 the disease spot on the pod is round or irregular, the black conidia disk is sometimes arranged in a wheel, the diseased pod can not develop normally, the seeds are moldy, dark brown and wrinkled or unable to bear fruit.

1.5 petiole disease symptoms petiole infected, spot brown, irregular shape.

2 the regularity of the disease

The pathogen overwintered on soybean seeds and diseased remains. After sowing in the following year, the diseased seedlings from diseased seeds produced a large number of conidia under wet conditions, which were infected and spread by wind and rain. The suitable temperature for the disease was 25-28 ℃, and the bacteria could not develop below 12-14 ℃ or above 34-35 ℃. In production, low temperature at seedling stage or excessive dryness of soil will delay the time of germination and emergence of soybean, which is easy to cause seedling disease. The warm and humid conditions in the adult stage are beneficial to the infection of the bacteria.

3 prevention and control technology

① selects disease-resistant varieties and carries out seed disinfection to ensure that the seeds are free of pathogens, reasonable close planting, and western fertilization technology to improve disease resistance. ② can drain water in time, reduce the humidity of soybean field, avoid applying too much nitrogen fertilizer, remove the disease and residue in time after harvest, carry out crop rotation for more than 3 years, and reduce the source of overwintering bacteria. ⑧ strengthens the field management, timely deep ploughing and mid-ploughing. Remove stagnant water in time after rain to prevent moisture retention. Before sowing, ④ was mixed with 50% carbendazim wettable powder with 0.5% seed weight, and the seeds were stuffed for 3 hours after mixing. It can also be sprayed after flowering with 25% trimethalin wettable powder 500x or 47% plus Renon WP 600x or 1 ∶ 1 ∶ 200Bordeaux.