Occurrence characteristics and control techniques of soybean red spider

The soybean red spider is a cinnabar spider mite, which belongs to the family Tetranychidae. Affected by high temperature and drought in 2007, soybean red spider occurred in an area of 120 million mu in Heilongjiang Province, resulting in a serious reduction in soybean production. According to the survey, in recent years, the damage of soybean red spiders has become the main position, generally reducing soybean production by 20-30% and serious plots by 70-90%.

First, morphological characteristics. The adult is 0.3-0.5 mm long, reddish brown and has 4 pairs of feet. The female mite is 0.5 mm long, oval or pear-shaped, slightly wider at the front, slightly pointed at the tail, long capillaries on the back, and a long black spot on each side of the back; the overwintering female is scarlet shiny. The male worm is 0.3 mm long, purplish red to light yellow, fusiform or pear-shaped. The egg is 0.13 mm in diameter, spherical, colorless and transparent at birth, and gradually turns yellowish and reddish. The young mites have 3 pairs of feet, the body is round, yellow and white, the oval shape is light green after feeding, and dark green spots appear on both sides of the back. If the mite foot 4 pairs, light green to light orange yellow, the back appears bristles.

Second, life habits. Soybean red spiders overwintered with fertilized female adults on soil crevices, weed roots and soybean plant residues. The activity began in the middle and late April of the following year, first propagated on small thistle, small spiral flower, dandelion, plantain and other weeds, transferred to soybean from June to July, propagated faster and spread rapidly with the increase of temperature from mid-late July to early August, and decreased gradually after mid-August. as the temperature dropped in September, it began to move to the overwintering place and began to overwinter in October.

Soybean red spider has 8-12 generations a year in Heilongjiang Province. The threshold temperature of development is 10.5 ℃, the upper limit temperature is 42 ℃, and the effective accumulated temperature of the first generation is 163.25 ℃. The development period from egg to adult is the shortest when the relative humidity is 35-55% and the average temperature is 22-28 ℃, which only takes 10-13 days. Therefore, the breeding speed is the fastest and the damage is the most serious when the drought lasts for more than 14 days. When the relative humidity is more than 70%, it is not conducive to the occurrence of red spiders, and the low temperature, rainy and windy weather is disadvantageous to the reproduction of red spiders.

Third, the characteristics of harm. Soybean red spiders can occur in the whole growth period of soybean, and the first spot occurs, in which adult mites and nymph mites gather on the back of the leaves to form a web and suck the leaf juice. Yellow and white spots appeared on the front of soybean leaves at the initial stage of injury, and after 3-5 days, the spots expanded and became dense, the leaves appeared reddish brown spots, local or even all curled, scorched and turned yellow or reddish brown, deciduous leaves and even light culms, and the whole plant died in severe cases. The plots with more nitrogen fertilizer are heavy. When there is lack of food, there is a habit of migration, and the damage peak occurs from July to August, and the plots with many weeds or poor plant growth occur more seriously.

Fourth, prevention and control methods. ① agricultural control: apply sufficient base fertilizer, increase phosphorus and potassium fertilizer, do not remove fertilizer in the later stage, remove weeds in time, drought and timely irrigation, conditional flood-drought rotation, can reduce the incidence of disease. ② chemical control: spot piece occurrence, soybean leaf roll plant rate 10% should be immediately used to control aphids, can be combined with the prevention and control of aphids to choose 73% mijing 3000 times or 40% diclofenac 1000 times or 25% paracetamate EC 3000 times or 20% acarine EC 2000 times spray, spray 2-3 times. Add 1% spray under drought conditions, plant spray auxiliaries Xiaobao, Xindebao and so on. ③ biological agent control: organic soybean can choose 1.8% avermectin EC, 0.3% azadirachtin EC 1500-2000 times, or 10% Yangmycin EC 1000-1500 times, 2.5% Huaguangmycin 400600 times, bionic pesticide 1.8% Nongke mite EC 2000 times spray, spray volume 1% botanical spray aids Xiaobao, Xindebao, etc.