What are the main pests and diseases that harm rhubarb?

The main diseases that harm rhubarb are ring rot, anthracnose, downy mildew and root rot. Pests include: Spodoptera litura, rhubarb and so on.

Disease and prevention:

(1) The diseased leaves of ring rot are nearly round, reddish-brown, and have concentric rings. In severe cases, the leaves will die. Prevention and control methods: ① Remove dead leaves and stems in winter and burn them centrally to reduce the source of overwintering bacteria; (2) Increase the application of organic fertilizer, timely intertillage weeding, and promote the healthy growth of plants; ③ Spraying 1∶2∶300 bordeaux mixture or 50 μ g/ml jinggangmycin two weeks after emergence.

(2) The diseased leaves of anthracnose are nearly round, the center is light brown, the edge is purple-red, and there are small black spots in the future. The control method refers to the control of environmental corrosion.

(3) The diseased leaves of downy mildew are polygonal or irregular, yellow-green, with no edges, gray-purple mildew spots on the back of leaves, and in severe cases, they will die. The onset began in the middle and late April, and it was more serious in May-June. Low temperature and high humidity are conducive to the onset. Prevention and control methods: ① rotation, timely ditch drainage after rain to reduce field humidity; ② Spray 40% Gao Ling 300 times or 25% erysipelas 400 ~ 500 times at the initial stage of the disease, and spray/kloc-0 once every 7 ~ 10 days for 2 ~ 3 times continuously.

(4) The diseased plants wilt and rot their roots, which is easy to happen when there is more rain in July and August. Prevention and control methods: timely drainage after rain; Loosen the soil regularly during the growing period to prevent soil hardening; During the onset of the disease, the roots of diseased plants were watered with 50% thiophanate 800 times solution to control the spread of the disease.

Pests and control:

(1) Spodoptera litura leaves. From June to July, 1 instar larvae eat epidermis and mesophyll, leaving only the upper epidermis and veins in a screen window shape. After 4 years old, bite the leaves into notches, leaving only the main veins. When the larvae mature, they enter the soil as a soil chamber to pupate. Prevention and control methods: eliminate egg lumps and newly hatched larvae in time during the occurrence period; Trap and kill with black light; Spraying 800 ~ 1000 times of 90% trichlorfon during the occurrence period.

(2) The adults and larvae of rheum officinale do harm to leaves, causing holes and affecting plant growth and yield. It occurs once a year and overwinters as an adult in host plants, weeds and soil cracks. Overwintering adults began to move at the end of April or early May of the following year, and died in August. Larvae occurs from June to September, and contemporary adults occur from late July to early September. Prevention and control methods: eradicate weeds; Clear the garden in autumn, winter or early spring, destroying the wintering habitat; Avoid continuous cropping, and it is better to take Chuanxiong or Astragalus as the wheel; The occurrence period can be controlled by spraying 500 times of 50% carbaryl wettable powder.