Control measures of soybean aphid disease

Soybean aphid is one of the main pests of soybean. Adults and nymphs are used to suck juice on the top leaves, tender leaves and stems of soybean plants. In severe cases, it is covered with stems and leaves, which can also infringe upon tender pods, resulting in dwarfism of plants, reduction of fruiting branches and pods, decrease of 1000-grain weight, and death of the whole plant at seedling stage. If it is not controlled in time in the big year, the yield will be reduced by 20-30%. If it is heavy, the yield will be reduced by more than 50%. The main soybean producing areas in China are all distributed, while the harm is more serious in some areas of Northeast China, Henan, Shandong and other provinces.

Soybean aphids suck juice with piercing mouthparts, so that the chlorophyll of the injured part of bean leaves disappears, forming a bright yellow irregular macula, and then the macula gradually expands and turns brown. The seriously damaged plants had curled stems and leaves, yellowing, short plants, and reduced branching and podding, thus affecting the yield of soybean.

First, the law of occurrence. Soybean aphids are divided into winged viviparous female aphids (0.9-1.6 mm body length) and wingless fetal female aphids (1.52-1.95 mm body length). Winged aphids can migrate and enlarge the scope of damage. The peak damage period of soybean aphids is at the end of June and the beginning of July. Generally, it began to appear in the soybean field in mid-late June, with continuous high temperature, drought and little rain, which is easy to cause a large number of aphids, and the more drought, the more serious the harm.

Soybean aphids occur 18 generations a year. In the north, the eggs are overwintered in the axils of aphids or in the gap between branches. The average temperature in the following spring and April is about 10 ℃, the plum buds are fresh and green, the overwintering eggs begin to hatch into dry mothers, and the parthenogenetic reproductive generations of dry mothers are 1-2 generations. In the middle and last ten days of May, after the bean seedlings were unearthed, the winged female aphid migrated to the soybean field and propagated parthenogenetic for more than 10 generations. The other part gives birth to winged male aphids on soybean, flies back to the overwintering host, and males and females mate and lay eggs over the winter.

Soybean aphids generally migrate four times a year, and accordingly there are several stages of growth and decline in soybean. For example, in the northeast, the first migration appeared in the unearthed stage of soybean seedlings, and the aphids moved to the soybean field from the winter host and occurred sporadically in the field. The second migration was in late June, when soybean aphids spread in Honda. Aphids have been distributed from point to surface, but the population density is not large, which is the early stage of the outbreak of bean aphids in the field. If the aphids can be controlled before the second migration, the damage can be controlled effectively. The third migration was in mid-July, when soybean blossoms, aphids rapidly spread to the whole field, and the number of aphids per plant increased sharply, which was the stage of occurrence of soybean aphids. The fourth migration was in September, and the number of aphids decreased as the climate and nutrition conditions gradually turned to be disadvantageous to aphids at the beginning of August. The winged female aphids began to fly back to overwintering parasites in early September.

Climatic conditions are the key factors affecting the fluctuation of soybean aphid population. According to the investigation in Northeast China, it can be divided into two stages: first, the overwintering hatching period from late April to mid-May, the survival period of young aphids and the breeding period of adult aphids. If Rain Water is full of plums, the survival rate of aphids is high and the reproduction is large. Second, from late June to early July, it was the early stage of the outbreak of soybean aphids, during which the average temperature reached 20-24 ℃, and the ten-day average relative humidity was less than 78%, which was very beneficial to the reproduction of soybean aphids and caused serious harm to the flowering stage.

Second, morphological characteristics. ⑴ adult: winged viviparous female aphid, long ovate, yellow or yellowish green, 1-1.5mm in length. There are significant milky processes on the side of the body, the frontal tumor is not significant, and the compound eye is dark red. The antennae are 6 segments, about the same length as the body, grayish black, and there are 6-7 secondary sensory holes in the third section, arranged in a row. The ventral tube is cylindrical and black, the base is twice as thick as the end, and there are tile-shaped wheels on it. Tail black, conical, slightly overflowing in middle, with 2-4 pairs of long hairs. ⑵ wingless viviparous female buds: body long oval, yellow or yellowish green, body length 1-1.3mm. The antennae are shorter than the body, and there is no secondary sensory foramen. The tail has 3-4 pairs of long hairs, and the other characteristics are basically the same as the winged viviparous female aphids.

Third, prevention and control technology. There are many natural enemies of soybean aphids, such as lacewings, predatory ladybugs, parasitic wasps and aphid flies, which can inhibit the growth of aphids when the number of natural enemies is large.

Attention should be paid to seedling prevention. 3911 emulsion or 40% methyl isosinophos emulsion can control aphids at seedling stage, as well as some other pests at seedling stage. In addition, seed coating technology can not only prevent aphids, but also achieve the purpose of increasing production.

The main results are as follows: 1. In the seedling stage, the spray of 125 g / mu of phosphorus-killing A has a significant effect on the control of soybean aphid without killing natural enemies. In order to avoid the resistance of soybean aphid, it can be used alternately with fenvalerate A 13 g / mu. 20% dimethoate EC or 50% aphid net EC or 50% phoxim EC diluted 1500-2000 times spray. 90% dimethoate EC or 88-90% acephate diluted 10 times, 350 grams per mu with ultra-low volume spray. 1.5% dimethoate powder or 5% carbaryl powder or 2% aldicarb powder, 1.5-2 kg per mu.

2. When spot damage occurs in soybean fields, you can use 1000 times of 40% dimethoate EC and 40% omethoate EC, or choose 2.5% dimethoate EC, 5% rifampicin EC and 10% deltamethrin EC, 225,300ml per hectare and spray water 600,750L.