Control of root-knot nematode disease of Platycodon grandiflorum

With the adjustment of industrial structure, the planting area of Platycodon grandiflorum is expanding. However, due to continuous cropping for many years, the occurrence of root-knot nematode disease tends to spread, which makes Platycodon grandiflorum lose its commercial value and reduce its economic benefits.

1 symptoms of disease

After Platycodon grandiflorum was infected with root-knot nematode, the symptoms of the aboveground part of Platycodon grandiflorum were not obvious when the disease was mild; when the disease was serious, the aboveground part showed poor growth, dwarfing, yellowing and wilting, like lack of fertilizer and water or Fusarium wilt, and when drought or evaporation was exuberant, the plant wilted at noon. After the seriously diseased plant is pulled up, it will be found that nodule-like root knot will grow on the root stem or whisker root, which is generally spherical in shape, the size of mung bean or soybean grain. Many small milky nematodes can be seen hidden in the root knot under the microscope, and thin new roots can grow on the root knot, which can be reinfected to form a root knot tumor.

2 the regularity of the disease

Platycodon grandiflorum root-knot nematode overwintered as eggs and larvae on soil, host and diseased body, and mostly lived in the depths of soil 5~30cm. The optimum temperature for survival was 25-30 ℃. When the temperature was higher than 40 ℃ or lower than 5 ℃, it was rarely active, but its activity was inhibited in dry or over-wet soil. It is mainly transmitted by means of diseased soil, diseased seedlings, diseased remains, soil fertilizers, irrigation water, agricultural tools and weeds. When the conditions are suitable, the overwintering eggs hatch into larvae in the root knot, the 1st instar larvae stay in the eggs, and the 2nd instar larvae drill out of the eggs and enter the soil to infect the tender new roots, and stimulate the host cells to expand to form root knots.

3 methods of prevention and control

3.1 one of agricultural prevention and control is rational crop rotation. Platycodon grandiflorum needs to grow for 2 ~ 3 years in terms of commercial value, so it is easy to rotate with wheat-summer corn (or summer sorghum) once a year. Second, strengthen field management. Thoroughly deal with sick and disabled bodies, focus on burning or deep burial, blisters, and reduce the source of infection. Third, be careful to apply fertilizer. Apply organic fertilizer without disease residue or fully mature to reduce the source of infection. Fourth, ploughing in deep winter. When farming is carried out in winter, the nematode larvae in the residual soil are turned to the surface and frozen to death by low temperature, so as to reduce the source of infection.

3.2 Chemical control one is soil disinfection. During soil preparation, use 3% millol granule 4~6kg or 5% aldicarb granule 3~4kg or 5% aldicarb granule 3~4kg mixed with dry fine soil 25kg to spread evenly, first sprinkle and then plow. Or 1.8% 450~500ml per mu before sowing, mix fine sandy soil and spread 20~25kg evenly, and then deeply plough 10cm, the control effect is better than 90%, no pollution to the soil, no residual toxicity to Platycodon grandiflorum.

The second is to fill the root. At the initial stage of the disease, the root was irrigated with 1.8% EC 1000 times and once every 10 to 15 days, which could effectively control the occurrence and damage of root knot nematode disease.