What causes the occurrence of thin-shelled pecan leaf borer?
Fund Project: 2011 Central Financial Forestry Science and Technology Promotion Demonstration Project "Thin-shell Pecan Breeding and Demonstration Forest Construction Technology Promotion" (Contract No.: [2011] TK046); 2012
Central Financial Forestry Science and Technology Promotion Demonstration Project "Thin Shell Pecan Yield Cultivation Technology Promotion demonstration" (Contract No.: [ 2012 ] TK36); 2017 Anhui Forestry Science and Technology Promotion and Innovation Project "Thin Shell Hickory Container Seedling Promotion Demonstration"
Chen Lei, Teng Huarong
The leafy bush borer is an important leaf-eating pest that harms the growth and development of thin-shelled pecans after the Star Sky Bull and the American White Moth. In June 2019, the pest was found in some thin-shelled pecan nursery areas in Fuyang, and due to the timely prevention and control and effective measures, no major losses were caused. Due to the concentration of eggs of the insect, the net of larvae is harmful, the amount of feeding is large, and the high egg laying site is not easy to find, it is easy to eat the leaves of a single plant in a short period of time, forming a whole bare plant in the local range, coupled with the leaf veins and leaf epidermis left by the larvae in the early stage of the pest, from a distance, the shape is like death, which not only affects the growth of seedlings, but also seriously affects the beauty of the forest. The pest is mainly concentrated in July and August, the temperature is high, the development is fast, and it is easy to cause outbreak hazards if it is not careful, and it is one of the main pests that the current scale and industrialization of thin-shelled pecans should focus on prevention and control. The occurrence of the pest and the control method are introduced as follows, for your reference only.
1 Name and host range
Locastra muscosalis Walker, also known as walnut leaf borer and woodworm, is a lepidoptera, family mothidae. The leafy bush borer prefers to eat walnuts, thin-shelled pecans, walnut catalpa trees, and at the same time harms a variety of forest trees: maple, yellow wood, yellow jujube, salt skin wood, yellow oak, plane tree, torch tree and so on.
2 Morphological characteristics
２． 1 Adult
Female adults are 14 to 18 mm long and spread their wings 32 to 36 mm. Male adults are 12 to 14 mm long and spread their wings 25 to 28 mm. The body is yellowish brown, the compound eyes are greenish brown, the antennae are filamentous, and the feet are brown. There is a black-brown transverse band in the middle of the forewing, serrated dark brown, the outer transverse line is curved like ripples, the inner and outer transverse lines are dark chestnut brown, the forewings have two black spots near the leading edge, the outer edge line is light grayish white, the sub-outer edge line is black, the middle chamber is grayish brown, the outer edge is dark gray to the shoulder angle, the base angle is dark brown, and the apex has a small yellow-brown eye spot. The hindwings are greyish brown , darker near the outer margin , gradually fading outward , with a crescent-shaped yellowish-white spot near the outer rim. Males have no villi at the anterior leg segments, while females have villi on the front legs.
２． 2 eggs
The eggs are oval in shape, the initial light bean is green, densely arranged into fish scales, laid on the back of the leaf, on both sides of the main vein, generally 1 to 100 eggs per egg. The egg shell is covered with a mesh of veins, has mucus, and sticks firmly.
２． 3 Larvae
The larvae hatch milky white, gradient milky yellow, and the head and hip plates are black. After each molting, the color gradually darkens. Mature larvae are 31 to 42 mm long, have a black, shiny head, and are about 3 mm wide.
The dorsal plate of the forebreast is dark brown with a light longitudinal groove in the middle. The dorsal midline is broad, apricot-red, the base color between the sub-dorsal line and the valve line is black-brown, with yellowish-brown markings between them, the valve line is brownish yellow to light yellow, the hip plate is black brown, the ventral surface and feet are dark yellow, and all have short white hairs.
２． 4 Pupae
Pupae are 12 to 19 mm long and yellow-brown, black-brown to black.
２． 5 Cocoons
Cocoon gray-brown, leathery, flat oval, 16 to 20 mm long, 8 to 12 mm wide, strong, similar to kraft paper.
3 Occurrence
In northern Anhui Province, one generation occurs a year, and the old mature larvae overwinter in the soil near the roots of thin-shelled pecans, and the soil depth is generally within 10 cm of the surface layer. Pupate occurs in late April and early May of the following year, with a pupal period of 20 to 25 days. Feathers into adults by the end of May and the beginning of June. Adults often feather in the early morning, are active at night, are most abundant in the middle of the night, fly quickly, and have strong phototropism. After feathering for 1 d, the tail is crossed, and the eggs begin to lay after 1 to 2 days, and the eggs are mostly laid on the back of the thin-shelled hickory leaves. Adults live 3 to 5 days and die after laying eggs. Generally, after 2 to 3 days and nights, multiple eggs are laid continuously on the adjacent leaves, and each piece has 30 to 100 eggs. The initial laying of eggs is light bean green, and after 24 hours of fertilized eggs, it gradually changes from green to red (unfertilized eggs do not change color), and becomes black-brown before hatching. The eggs hatch the larvae after 7 to 10 days, and the hatching rate is about 95%. Mid-June is the incubation period for larvae, late June for larvae for pests, and mid-July for the peak of pests. An egg hatches dozens to hundreds of larvae, and the hatching larvae form a large nest that sticks together nearby branches and leaves, licks the leaf flesh, and retains the epidermis and reticular veins. At this time, the larvae are active, wandering around on the leaves in the net during the day, molting and excreting all in the net curtain. Most of the harmful leaves are located on the periphery and middle upper part of the canopy and are not easy to detect. 1-2 instar larvae feed in small amounts and feed only on leaf flesh. After 3 years of age, the amount of food increases, and only the leaf veins are retained in the feeding leaves. A life history of a leafy borer larvae can 20 to 30 cm2 and a thin-shelled hickory compound leaf size. The larvae increase by one year in about 4 to 5 days, a total of 6 instars, and the same batch of egg blocks hatched larvae, molting time is more concentrated. The carcass of the larvae is white at the beginning of the molting of each age, and gradually recovers its color from the skull after about 30 to 40 minutes; after 3 years, the larvae begin to divide into small groups, decorate the leaves into a barrel, and feed in the cylinder when they are stationary; after the 4th instar, the larvae mostly feed and transfer at night, lie still on the leaves or in the net during the day, and occasionally crawl out of the ground string when frightened. In early August, the old mature larvae successively descend the tree to find a suitable cocoon in the soil, the larvae spit silk to make a cocoon for 3 to 5 days, the larvae curl up in the cocoon and sleep for overwintering, and the old mature larvae hibernate for 230 to 240 days. The life history of the leafy bush borer is shown in Figure 1;
Figure 1 Life history of thin-shelled pecans in northern Anhui Province
3 Prevention and control methods
３． 1 Physical control
３． １． 1 Clear the host
Remove peripheral symbiotic or host rhizosphere cocoons and canopy larvae. According to the types of trees around the site of Fuyang, camphor is a parasitic tree species of the leaf bush borer, and it is more harmful. Peach trees and other green tree species need to be further observed.
３． １． 2 Lights trap adults
From late May to mid-June, adults are booby-trapped by black light lamps during the adult occurrence period and eliminated in time.
３． １． 3 Picking mesh screen
The larvae of the leafy bush borer are often networked in the upper and outer parts of the canopy, and the leaves are concentrated as pests. In plots with lighter net curtains in the previous year and fewer net screens in that year, the net curtains can be manually picked or the insect branches can be cut off with hooks and sickles to concentrate on eliminating the larvae.
３． １． 4 Dig up the cocoon
Depending on the number of canopy nests, dig up cocoons at the rhizosphere of the canopy. The cocoons of the leaf-studded bush borer are generally concentrated next to the roots of the tree or in the soft soil, and are dug up and sorted before freezing or after thawing, and are destroyed in a concentrated manner.
３． 2 Biological control
３． ２． 1 Protect and utilize predators
There are many natural enemies of the leafy bush borer, which can be fully utilized: the natural enemies of the egg stage include ladybirds, wattles, and praying mantises; the parasitic natural enemies in the larval stage include bees, cocoon bees, hook-bees, etc.; predatory bird predators are:, sparrows, thrushes, gray magpies, yellow orioles, bald eagles and other beneficial birds.
３． ２． 2 Spray biological agents
According to the "Biological Characteristics and Its Prevention and Control Of the Leaf Bush Borer" published by Ke Zhiguo of the Wuhan Institute of Botany of the Chinese Academy of Sciences, a variety of bacteria, viruses and fungi can restrict the occurrence and spread of the leaf bush borer. The larvae of the leafy bush borer can be sprayed with white zombie powder during the infestation stage, and the larvae are sprinkled with white zombie powder on the ground under the canopy at the mature stage, and then shallow ploughing loose soil to eliminate the mature larvae in the soil. In the early to mid-June larval incubation period, 1 500 to 2 000 times 2% avermectin emulsion or 1% methyl vitamin salt 1 000 times liquid + permethrin pesticides were used, and the control effect was good. At the same time, according to the control tests of Ke Zhiguo and others, plant pesticides such as neem oil have obvious food rejection effects on leaf bush borer, especially 250 times bitter bark vine emulsion and triptolide root powder leaching solution, and the food rejection effect is more than 95%.
３． 3 Chemical control
３． ３． 1 Spray control
6-7 months larvae for pests peak period, 2. 5% bromocyanid chrysanthemum vinegar 3 000 ~ 5 000 times liquid, 90% dimethodium 800 times liquid or 50% octylthion emulsion 1 000 ~ 2 000 times liquid, 5% imidacloprid emulsion 2 000 ~ 3 000 times liquid, sprayed nest by nest at 8-10 a.m. on sunny days, the control effect is good.
３． ３． 2 Trunk injection control
During the peak of pests, in different directions at the base of the trunk, according to the thickness of the tree, drill 4 to 8 holes with electric drills, up to 2 to 4 cm deep in the xylem, at an angle of 50° with the trunk, depending on the age of the insect and the density of the insect mouth, the size of the plant, inject 40% acephthateminophos (or oxidized fruit) stock solution with a syringe 4 to 6 mL, and fill the hole with wet clay in time. While controlling the leaf bush borer, it can also treat thorny mouthpart pests such as stinging moths, aphids and leafhoppers.