Our Weicheng District is a traditional agricultural county. The output of corn affects the income of farmers to a certain extent. Therefore, the cultivation technology of corn is a serious issue for us.

Both Tetranychus urticae and Tetranychus cinnabarinus are distributed throughout the region.

【Injury symptoms】

If the plucked clams and pods clustered on the back of the leaves, the leaves were gray or withered yellow spots. In severe cases, the entire leaves yellowed and shrunk until they had fallen off and the corn kernels were thin and thin, resulting in reduced yields and no harvest.

【Morphological characteristics】

Two-spotted spider mites: females become pale green, brownish green, dark brown, orange-red and other colors; each with a dark red long spot on both sides of the body, sometimes the central spot color is divided into two before and after. Females are oval in shape, mostly dark red, and yellow-brown; overwintering is orange-yellow, which is more hypertrophic than summer type. The males became nearly ovoid, with a rounded front end and a sharper abdomen, mostly bright red. Oval, smooth, colorless, transparent, orange-gray, will appear red eyes when hatching. When the hatchlings hatched, they were nearly round, colorless and transparent, darkened green after feeding, and their eyes were red. There were 3 pairs of feet. If the corpus callosum is nearly ovoid in its early stages, the color becomes darker, and spots appear on the back of the body; if the corpus callosum is yellow-brown in the later stages, it is similar to the adult.

Cinnamomum cinnamomea: Oviductus into female ellipse; both sides of the abdomen have a three-striped long dark brown large spot. Male into a body diamond, usually red or rust red, but also dark green yellow, full 4 pairs. The eggs are nearly spherical, initially colorless and transparent, gradually becoming light yellow or orange-yellow and slightly reddish before hatching. Juvenile and Ruoqiang: After the egg is hatched, it is l-year-old and only has 3 pairs of feet. After the larvae become 2 instars, they are also known as early quails. If the primordial pupa is crushed, it is 3 years old and is called the late quail. If the quail has 4 pairs of feet, the raccoon has only 1 pelt in its lifetime, only the previous period. Hey. Cub yellow, round, transparent, with 3 pairs of feet. If the carcass looks like a beak, it has 4 pairs of feet. The body color is light in the early stage and it turns red in the late stage.

Occurrence rule

Two-spotted spider mites: More than 20 generations in the South and 12-15 in the North. Overwintering sites vary from region to region. Female adults in weeds, litter and soil seams in northern China are lurking and wintering; wintering occurs in weeds and bark seams in central China; females in Sichuan Adults overwinter on weeds or peas, broad bean crops. When the average temperature reaches 5-6 °C in February, the overwintering females begin to move. From March to April, they first feed on weeds or other infested objects. They migrate to Guadalupia from late April to mid-May. Spots occur first. Then spread the whole field. The period from mid-June to mid-July is the period of damage. The cornfields near the villages, orchards, greenhouses, and weeds along the Xiangyang Ditch occurred early and heavy, followed by perennial dry fields.

Cinnamomum cinnamomea: 12 to 15 generations a year in the north, 18-20 generations in the Yangtze River basin, and more than 20 generations in the South China region each year. In the winter, up to a thousand heads can be clustered together through the clustering of female larvae in the grass roots, dead leaves and earth cracks or bark cracks. With the arrival of the rainy season in mid-July, the occurrence of leafhoppers has been rapidly reduced. If the weather is dry in August, it will happen again. Severe droughts and heavy rains occur; heavy rain has a significant inhibitory effect on the occurrence of C. verrucosa; the rotation field is light, and the plots adjacent to or interspersed with melons and fruit trees are heavier.

[control methods]

Arrange rotation crops and intercropping and interplanting crops in a rational manner to avoid the mutual transfer of leafhoppers between hosts. The best results are for paddy and dry rotations. Strengthen field management, keep the pastoral clean, timely eradicate the weeds in the fields and old leaves of dead branches and burn them, reducing the source of insects. Drought should pay attention to irrigation, increase the humidity in the field, is not conducive to its reproduction and development. In combination with field management, it is easy to erase the leaves when they are found; if the amount of wax is large, the leaves are removed. After harvesting, the debris, defoliation, and weeds in the field were promptly removed and burned centrally. Where conditions permit deep plowing and winter irrigation.

After the jointing stage of corn, the amount of single plant insects reached more than 200, and sprayed with pesticides. The following agents can be used: 15% of Lingling EC 2000-2500 times; 73% of Ketek EC 2000-3000 times; 20% of fenpropathrin EC 1000-2000 times of liquid; 20% of compound Liuyangmycin EC 1000 - 2000 times liquid; 20% amitraz EC 1000-1500 times; 2.5% Lambda-cyhalothrin EC 2000-4000 times; 2.5% bifenthrin EC 3000-4000 times; 5% Thiophenone Emulsion 2000-3000 times; 1.8% avermectin EC 3000-4000 times; 20% dicofol EC 600-1000 times, spray 7-10 days 1 time, continuous 2-3 times. Pharmacy should be used in rotation to avoid drug resistance. The spraying should be uniform, it must be sprayed to the back of the leaf; in addition, the host plants such as weeds on the field must also be sprayed to prevent its spread.

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