1 taxonomic status and morphological characteristics of geometrid
Semiothisadne~anaBremeretGrey belongs to the Geometridae of Insecta, Lepidoptera. The adult is 12~17mm long and its wings spread 3 ~ 45 mm. The body is grayish brown and the antennae are filiform. The mouthparts are developed, and the lower lip must be multi-mouthed, protruding from the head. The sub-baseline and midline of the front wing are dark brown, and both near the leading edge bend sharply to the outer edge to form an acute angle, which is composed of dark brown patches. The sub-baseline of the hind wing is not obvious, and the midline and sub-outer edge lines are arc-shaped and dark brown. Oval-shaped, .58-''.67 mm long and .42-.48 mm wide, green at first birth, then gradually dark red to grayish black, and transparent shell. Larvae has 3 pairs of thorax feet and 2 pairs of abdomen feet. It is yellow-brown when it is first hatched and green after feeding. The 2-5 instar larvae are all green, and the mature larvae are 2~4mm long, and their backs turn purple. The pupa is 13~16mm long, pink at first, and gradually turns purple, with 2 buttock spines.
2 Harmful symptoms of geometrid of Sophora japonica
1-3 years old insects eat less, and the larvae of the first 9 days often burrow into the bud to feed on young leaves, which are reticulate and can spin down, and spread to orchards and fields in the downwind direction with the wind, endangering crops such as agriculture, fruits and vegetables: after 3 years old, their food intake increases sharply, leaving only midvein for feeding on mesophyll. The amount of leaves eaten in the whole larval stage is equivalent to the weight of a compound leaf, so as long as there is one worm in each compound leaf on average, all the leaves can be eaten up. The geometrid of Sophora japonica is a gluttonous pest of Sophora japonica. When it occurs, it can eat all the leaves in a short time.
3 the life history and habits of geometrid
geometrid has three generations a year in western Henan province. Overwintering with pupae, overwintering pupae emerged one after another in mid-April, the first generation larvae appeared in May, and the first generation larvae reached the peak in mid-May, while the second and third generation larvae reached the peak in early July and mid-August, respectively, and the pupation peak of each generation was in the middle and late May, mid-July and late August. By the end of September and early October, a small number of larvae were still pupated. Every April, the overwintering pupae emerge in the evening, and mate on the same day after emergence, mostly at night, lasting about 3min, and they are separated when they are frightened. The geometrid of Sophora japonica has the habit of supplementing nutrition, and the amount of eggs laid is related to the supplementary nutrition. The number of eggs laid by adults with supplementary nutrition is 2~3 times higher than that of hunger strikers. It is observed that adults generally like to feed on begonia flowers to supplement nutrition. The life span of male adults is 3-19 days, and that of female adults is 3-17 days.
the seeds are scattered on leaves, petioles and branchlets, and most of them are in the south of the crown. Most of the eggs are laid at 19 ~ 2 o'clock, and the same female moth lays eggs regularly. When the egg is born, it is green, gradually changes to dark red with grayish white stripes, and finally becomes grayish white. There is a black stripe around the egg shell, and the middle of the egg is obviously sunken. This kind of egg hatches the next day or the same day.
larvae begin to feed on leaves after hatching. Larvae spin and droop, drift with the wind or cling to the tree by chest feet and two pairs of abdomen feet. After the 5th instar, the back of the larva appears purplish red, which indicates that the larva is ripe. After ripening, they lose the ability to spin silk, and often climb down the trunk or fall to the ground during the day to pupate in the soil. The pupation sites are mostly located in the vertical projection range of the crown, with the southeast of the crown being the most. Under the condition of soft soil, the depth of most larvae is 2-5cm, and a few are 12cm. The larvae of urban street trees mostly pupate under hedgerows and on the floating soil at the root of walls. When there is no suitable pupation place, it can also be pupated on the bare ground, but the survival rate is very low.
4 comprehensive control techniques of geometrid of Sophora japonica
4.1 artificial control
The pupae of geometrid of Sophora japonica mainly live in soft, moist, shaded and defoliation-covered environment, and most of them are at a depth of 3-5cm. Therefore, manual pupation can be adopted for control. The suitable time for digging pupae is from September to early November of that year or from the end of February to the end of March of the following year when the weather gets warmer. If the pupation stage of the second to third generations is combined, the effect of pupation digging will be better. When digging the pupa, find the habitat of the pupa. Use a small wooden stick, a small iron stick or a small flower shovel to gently stir the soil and fallen leaves in the soft soil with a depth of 3~5cm to find the pupa. Concentrate the pupae in plastic bags and seal them, then burn them, or dig a pit 5cm deep and bury them. Protein content of the pupa is high. If the pupa is large, it can be sold or sent to a nearby chicken farm. This work must fully mobilize the masses and carry out large-scale corps operations. According to the characteristic that the geometrid of Sophora japonica has suspended animation, that is, the silkworms droop, the larvae can be killed by vibrating trees, and when the mature larvae get off the trees and pupate, they can be killed manually.
4.2 agricultural control
destroys the ecological environment of pupae and reduces the hatching rate of larvae. Build a 2mX2m weir under the trunk of street trees, and lay a pedestrian walkway with nine bricks to destroy the habitat of insect pupae. Every autumn and spring, the dead branches, fallen leaves and floating soil under the hedge should be removed in time (that is, soil falling). Strengthen the management of tree maintenance, and prune trees according to the technical operation procedures, especially the pruning of flowers and shrubs near Sophora japonica, so as to make them well ventilated and transparent. The requirement of Sophora japonica for soil conditions is that the soil layer is deep, the drainage and ventilation are good, and the soil with strong alkalinity and high viscosity is not suitable for planting Sophora japonica. Apply organic fertilizer before sowing, and apply organic fertilizer at the same time when sowing. Topdressing is mainly inorganic quick-acting fertilizer. Avoid planting begonia plants in Sophora japonica cultivation areas, so that adults can not supplement nutrition in time and reduce the amount of eggs laid by adults. It is not allowed to plant Sophora japonica, Sophora spinosa, Sophora japonica and Sophora japonica in the same place at the same time.
4.3 biological and physical control
wasps often prey on geometrid of Sophora japonica in breeding. From the end of July to the beginning of August, one end was tied with straw and wheat straw to make a nest shed. The nest shed was 2．5m above the ground and fixed on a tree trunk or wooden stake. At night, it was taken back in a cloth bag and put in the forest. According to the research, placing 45 nests/／hm2 can control the inchworm of Sophora japonica well, but the management of urban gardens is prohibited. You can also put the eggs laid by Chrysopa Chrysopa for 2 days, and release them in the forest when their bases turn gray. When released, they can be tied or stuck to the plants with paste. The resistance of Chrysopa grandis adults is very poor, so chemical control should try to avoid using drugs in May-June. When larvae occur, 1 billion spores/g of Bacillus thuringiensis powder is used to dilute water 2 times and spray it. The temperature above 3~(2) is the best. Mixed with trichlorfon and pyrethroid pesticides has good effect. Taking the medicine once in May and July can basically control the harm. The adult geometrid of Sophora japonica has obvious phototaxis. According to this habit, the garden department specially designed and produced a beautiful, economical and practical light trapping device, which was placed in the area where pests occurred heavily to trap and kill by light. Under normal circumstances, more than 3 integrated worms can be lured every night. At the peak of eclosion with high temperature and good weather conditions, more adults were trapped.
4.4 chemical control
before the 4th instar, pay close attention to whether the leaves at the top and edge of the crown have been nibbled or not. If yes, it shows that the average killing rate of leaves exceeds 5%. At this time, spraying equipment should be prepared and spraying prevention should be started. The larvae can be killed by spraying with 1 times of 2% diflubenzuron No.3, or 1 times of 4% hypertonic omethoate, or 4 times of 2% Juma EC, or 2-3 times of 5% Phoxim EC, or 15-2 times of 5% Butachon EC. Try to spray evenly when spraying. For underground larvae, 2.5% trichlorfon powder and 3% dimethoate powder were sprayed on the ground. Mature old larvae are the most favorable time to control the inchworm of Sophora japonica, which can be cleaned and killed before the mature larvae enter the soil. Or combine with loosening the soil in autumn, find pupae in 2cm thick soil layer and treat them centrally to reduce the source of insects and reduce the harm in the next year. You can also spread 5% zinc-sulfur-phosphorus granules 3 ~ 5g/m2 on the soil surface under the tree, and hoe it once to make the pesticide granules enter the soil layer to kill the insect pupae. In areas where trees are planted alone or it is not suitable for spraying, 4% monocrotophos can be injected for prevention and control, and the effect is good.