Walnut leaf-eating pests mainly include walnut leaf borer, American white moth, wood tamarind inchworm, thorn moth, water cyan moth and so on. Larvae endanger leaves, often cluster hazards, resulting in eating leaves within a few days, seriously affecting the potential and yield of walnut trees.
1. Walnut leaf borer
It is also called leaf bush borer, wood maple armyworm and so on. It belongs to lepidoptera, family Moths, and is a genus of leafy clump borers. In recent years, the northern walnut has been more and more seriously damaged by the leaf borer, and there has been a disaster, the general damage rate is 50% to 80%, and the density of a single insect mouth in severe cases is more than 3,000 heads; the leaves are harmed by larvae, and all the leaves can be eaten up in serious cases.
(1) Symptoms of harm. The affected leaves are mostly located in the upper and outer parts of the canopy, easy to find, with larvae to harm the walnut leaves, after the plant is killed, the branches are broken, the nets are rolled, covered with insect feces, the crown is bare, resembling fire, leaving a Nestle-like nest on the branches, and in severe cases, within a few days, all the leaves can be eaten (Figure 1).
Fig. 1 Walnut leaf borer larvae and hazards
(2) Prevention and control methods. Artificial control. Remove the buds. When the larvae are endangered in groups, the buds are found, removed in time, and burned in a concentrated manner. Using the habit of adult insects laying eggs on the periphery of the canopy and decorating leaves to form a nest, the nest net can be cut off to eliminate some of the larvae.
Physical control. Taking advantage of the phototropism of adult insects, during the peak of adult feathering from late June to early July, lamps are set up to trap and kill adult insects.
Pharmaceutical control. In the early stage of the larvae in mid-to-late July, the larvae can be sprayed with 50% (mass fraction, the same after) dichlorvos emulsion 1000 times liquid, or 25% ceivine wettable powder 500 to 800 times liquid, and focus on spraying the nest net on a sunny morning, with better results.
2. American white moth
Also known as american lamp moth, autumn caterpillar, autumn curtain moth, belongs to lepidoptera, lamp moth family.
(2) Hazard symptoms. The hatching larvae spit silk into a net, and the group is harmful, and each tree can reach hundreds or thousands. Larvae often eat away at the leaves, seriously affecting tree growth (Figure 2).
Figure 2 American white moth larvae and hazards
(2) Prevention and control methods. Strengthen quarantine. Active prevention and control in the epidemic area to effectively control the spread of the epidemic. Seedlings in the affected area are not quarantined or treated and are prohibited from being transported.
Artificial control. Before the larvae are 3 years old, the net curtain is found, and the net curtain is manually cut and processed centrally. If the larvae have been dispersed, before the old mature larvae pupate, at 1 to 1.5 meters from the ground from the trunk, tie it tightly with grain grass, straw or grass curtain, lure the larvae of the tree pupa, during the pupa, change the grass handle every 7 to 9 days, and the unsolved grass handle should be burned or buried deeply, and the regular centralized treatment.
Trapping. Traps are used to trap adults during the feathering phase of adults. Insect trap lights should be set in the previous year when the occurrence of the American white moth is more serious, and the surrounding empty plots can obtain a better control effect.
Pharmaceutical control. Pharmaceutical control works best before the larval 3-year colony has dispersed. Optionally, 0.12% propylene glycol alginate (algae cap), or 2.5% high performance cypermethrin microemulsion 1500 times liquid, or Bt emulsion 400 times liquid, or 2.5% high efficiency cypermethrin emulsion 1500 times liquid spray. Can effectively control pest damage.
Third, the wooden scale inchworm
Also known as the wood maple step, the wood maple ruler moth, the walnut inchworm, the acacia inchworm, commonly known as the hanging ghost, the measuring ruler, the small big head worm, the stick worm. It belongs to lepidoptera, Ulmus ulnar moth family.
(1) Symptoms of harm. It is a bulivorous pest on walnut trees, mainly feeding on the leaves with larvae, and when it occurs severely, the whole leaf piece can be eaten in 3 to 5 days, leaving only the leaf veins and petioles, which seriously affects the tree potential and yield (Figure 3).
Fig. 3 Larvae and hazards of the inchworm inchworm
(2) Prevention and control methods. Artificial planing pupae. In areas with high pupal density, in early autumn or early spring, after leaf fall to before freezing, after thawing in early spring to before feathering, combined with the ground repair weir, artificial pupae are organized, and pupae are dug within 1 meter around the tree to suppress the amount of insects. Before the adults feather, turn over the tree tray or cover the mulch under the canopy to prevent the adults from emerging.
Trapping. During the feathering period of adult insects from May to August, black lights (200 watt electric lights can also be used) are set up at night to trap adult insects by using the phototropism characteristics of adult insects. It can also be artificially caught in the early morning, or shaken down to kill the larvae.
Pharmaceutical control. Grasp the egg hatching and the critical period of young larvae for spraying, the larvae before the 3rd instar insect mouth density is small, the amount of food is small, the harm is small, the resistance to drugs is relatively poor, and it should be sprayed in a timely manner. It can spray 90% of the dimethoate 800 to 1000 times liquid, or 5% high-efficiency cypermethrin emulsion 3000 times liquid, or 20% chrysanthemum emulsion 1500 to 2000 times liquid, or 20% juma emulsion 2000 times liquid, can be used 1 to 2 times, at an interval of 7 to 10 days; rotation of medication to delay the production of resistance, have a better control effect.
Biocontrol. The release of red-eyed wasps in July and August can play a certain role in controlling pests.
4. Thorn moths
It is also called spicy seeds, hairy pepperworms, flat-spined moths, octagonal worms and so on. It belongs to the family Lepidoptera , with about 500 species ; it is an important leaf-eating pest.
(1) Symptoms of harm. The leaves are harmed by larvae, and the young larvae eat the leaf flesh and leave the leaf veins; slightly larger to eat the gaps and holes; in severe cases, the leaves can be eaten, leaving only the petiole and the main vein, which seriously affects the walnut tree potential and fruit development (Figure 4).
Fig. 4 Larvae and hazards of the stinging moth
(2) Prevention and control methods. Artificial control. 1) Handle the larvae. A variety of thorn moths such as the green thorn moth, the green thorn moth, the longitudinal whiskered thorn moth and other juvenile larvae, multi-cluster feeding, the affected leaves appear white or translucent patches, etc., easy to find, at this time near the plaque, often inhabit a large number of larvae, in the small larvae cluster leaf back damage, timely removal of insect branches, leaves, concentrated destruction treatment, killing larvae, the effect is obvious. Many mature larvae of thorn moths often descend along the trunk to the dry base or the ground to form a cocoon, which can be removed in time by means of trunk binding grass.
2) Remove the overwintering cocoon. During the period when the mature larvae are looking for a cocooning place, the human being is organized to kill the mature larvae; the cocoons are collected and treated intensively. The cocoon period of the overwintering generation of the thorn moth is more than 7 months. At this time, the fruit farmers are more idle, summer (1st generation area) and winter and spring (1st to 2nd generation area) combined with pruning and other production operations, according to the similarities and differences of different moth species wintering places, using knocking, digging, shearing and other methods to remove the insect cocoon; the insect cocoon can be concentrated with a yarn net, so that the natural enemies of pests feather out, and the cocoon parasitic by the green bees is picked out for protection and utilization; in order to avoid the harm of poisonous hair on the cocoon, the cocoon can be buried in a 30 cm deep soil pit, and buried in the ground.
Light booby-trapping. Most adult stinging moths have strong phototropism, and can be used to trap adults in the feathering period and use black light to trap them at 19-21, which is better.
Pharmaceutical control. Severe garden tablets are sprayed during the larval stage. The larvae of the thorn moth are sensitive to the agent, generally touch killers can be effective, in the young age of the larvae, can be foliar sprayed 300 ~ 500 times liquid Bt emulsion once, 10 days later, and then spray 25% pyrifos urea No. 3 2000 times liquid 1 time; larval harm peak, the canopy can be sprayed 90% of the enemy insects 800 ~ 1000 times liquid, or 20% rapid killing of 2000 ~ 4000 times liquid, or 80% of dichlorvos emulsion 1200 times liquid, or 2.5% cypermethrin emulsion 5000 times liquid, or cyanobacteria 800 times liquid It can also spray insecticides such as scavengers, which can control pests.
5. Water moth
Also known as the Great Water Moth. It belongs to lepidoptera, silkworm moth family, long-tailed water cyanotic moth genus.
(1) Symptoms of harm. The larvae encroach on the leaves and, in severe cases, eat the leaves quickly (Figure 5).
Figure 5 Larvae, adults and hazards of the water moth
(2) Prevention and control methods. Manual hunting. The larvae are large, non-toxic, large fecal grains, easy to find, and can be organized for artificial capture; after the winter leaves fall, the overwintering cocoons hanging on the trees are picked in time to use the nest silk.
Pharmaceutical control. In each generation of juvenile larval stages, 90% dimethoates can be sprayed with 800 times liquid, or 20% rapid extermination 2000 to 4000 times liquid, or 80% dichlorvos emulsion 1200 times liquid, or 2.5% cypermethrin emulsion 5000 times liquid. (Source: New Technology of Fruit Tree Cultivation, Friends of Fruit Growers)
Edit: Ren Jing