There are relatively few pests and diseases of walnuts. Common ones include rot, canker, beetle, inchworm, and scale insects. The prevention and control methods are: promptly cut off diseased and insect-infected branches, dry and dead branches and burn them in a concentrated manner in winter. Do a good job in clearing the garden to reduce the sources of pests and diseases; spray 600 times the amount of dimethoate solution when the larvae hatch from early spring to early summer, which can prevent and control pests such as beetles, inchworms, and scale insects; scrape off the infected bark with a knife at the end of autumn, and apply 100 times Familiar Arsenic Liquid can prevent and treat dry rot, canker and other diseases.

1. Walnut canker

Walnut canker can be prevented and treated by removing diseased branches and leaves, scraping off the rough bark at the base of the trunk, applying 5-10 Baume degrees lime sulfur mixture or 50% thiophanate methyl, and then Spraying 50% 800 times solution of 50% Bactericide twice from July to August can reduce the disease rate to less than 1%.

2. Walnut limb-lifting moth.

The main damage is to fruits. The larvae eat into the green skin and eat many tunnels, which are filled with insect feces. The green skin turns black at the damaged area. The seed kernels shrink and fall early in the early stage of the damage, and turn black in the later stage. , commonly known as "walnut black". There are 1-2 generations in a year. The mature larvae spin cocoons in the soil and overwinter. They pupate from mid-May to mid-June of the second year. Adults occur in early June and mid-to-early July. The larvae usually appear in June. The middle period is the peak period of harm. The egg stage lasts for 4-5 days. The larvae only stay on the fruit surface for 3-4 hours before worming their way into the fruit. They remain in the fruit for 30-45 days and then fall off the fruit. The occurrence of this insect is closely related to rainfall. During the adult emergence period from May to June, if the rainfall is less than 30 mm, the occurrence will be light, and vice versa.

Prevention and control methods: (1) Manual control. Remove diseased fruits in time before August; clear the garden thoroughly before winter and plow the soil to eliminate overwintering cocoons; during the adult emergence period, use sex attractants to trap male adults to reduce mating and reduce the population density of offspring. ②Pharmaceutical prevention and control. Sprinkle toxic soil into the tree before the adults are unearthed, and lightly hoe after applying 25% phoxim microcapsules; use 25% carbaryl every 10-15 days during the peak spawning period (early June to early July) Spray the trees with 400-500 times of wettable powder, Bt emulsion, etc. (2) Adopt a comprehensive prevention and control plan based on cultivating under trees and removing fallen branches and leaves, picking black fruits as the main measure, and canopy spraying as an emergency measure. That is, plowing, expanding and clearing the garden from the time of fruit picking to mid-May of the following year; picking black fruits from June to August and destroying them in a centralized manner; selecting 50% of the fruits in the worst-hit areas during the adult emergence period from early June to mid-July. Spray the canopy with 1,000 times to 1,500 times of fenitrothionate solution or 3,000 times of enemy killing solution.

3. Cloud-spotted beetle.

The larvae feed on the trunk of the tree, while the adults damage the tender bark and leaves of new shoots, and in severe cases, cause the tree to die. The vigor of the injured trees weakens, the yield decreases, and the wood loses its utilization value. 1 generation every 2 years. The insect overwinters as an adult or larvae in the damaged tree trunk. It begins to be active in mid-April. May is the peak adult emergence period. Mid-to-late June is the peak egg-laying period. It pupates in August and emerges as an adult in September.

Prevention and control methods: ① Adults can be captured manually, and insect holes can be plugged with pesticides in time to kill eggs and larvae. In August, trees can be sprayed with 40% insecticidal net solution 500 times, and the control rate can reach 90% %above. . Adult insects have phototaxis and suspended animation habits, and are lured under the tree with lights at night to kill them; during the larval egg-laying period, the eggs and larvae in the crescent-shaped egg-laying grooves on the tree trunks are scraped; during the larval damage period, the wormhole diaphragms are found to remove feces, Use a cotton ball dipped in dichlorvos solution to stuff into the insect hole, and then seal it with mud and it will have a good insecticidal effect. ② In winter or before the spawning period, mix thoroughly with 5 kg of quicklime, 0.15 kg of sulfur, 0.25 kg of salt, and 20 liters of water, and then paint the base of the trunk to prevent adults from laying eggs and also to kill the larvae.

4. Walnut root elephant is also known as Henggou elephant.

It occurs in walnut-producing areas of Sichuan, and is particularly serious in Guangyuan City and Bazhong City. The damage is more severe in valleys at the bottom of slopes, in fertile soil areas near villages, and in vigorously growing walnut trees. Because the insect feeds in the cortex of the neck of the walnut root, it destroys the conductive tissue of the tree and hinders the normal transportation of water and nutrients, resulting in weakening of the tree. In mild cases, it will reduce yields, and in severe cases, it will cause the death of the tree. Symptoms of damage are that when the larvae first start to harm, the root neck cortex does not crack, no insect feces and sap flows out, and there are adult emergence holes the size of soybean grains in the root neck.

When the damage is severe, many insect canals in the cortex are connected and filled with dark brown fecal particles and sawdust. The damaged bark layer splits vertically and brown sweat is shed. This insect has one generation every two years in Sichuan and Shaanxi, and it takes three years to overwinter as adults and larvae in the root cortex. Overwintering adults begin to move from late March to early April, feeding on leaves and twigs to replenish insect nutrition. May to October is the egg-laying period, and 90% of the larvae are concentrated in the root cortex 5-20 cm deep under the surface soil. The damage depth of individual larvae can reach 45-60 cm of the main root, and the lateral roots are also harmful 140-200 cm away from the main trunk. The larvae have a long harmful period and can eat from March to November every year. The overwintering period is from December to February of the following year. The larvae are white, legless, and slightly curved.

The prevention and control method

From April to June, dig out the soil at the roots and stems, chop the cortex every 10 centimeters or so with an axe, and paint the affected areas with Walnut Baoguoling No. 1 The parts are then re-soiled to kill the root larvae; before the beginning of winter, the litter and weeds in the lower part of the crown are completely removed, the old bark at the base of the trunk is scraped off, and burned intensively. Tilling the soil under the trees will eliminate most overwintering larvae. In spring, before the infected young fruits fall off, cut them off in time, pick them and bury them deeply to reduce the insect population density in the following year.

5. Walnut longhorned beetle

The scientific name of the long-spotted longhorned beetle is also called the long-spotted longhorned beetle and the iron cannon bug. It is distributed in the walnut producing areas of Sichuan. It mainly damages branches and trunks, with the rate of damaged plants reaching 95% in serious areas. Some of the main branches of the injured trees died, and some of the main trunks died as a result of the damage.

Symptoms of damage include slight cracking of the cortex of the affected area and the discharge of large amounts of feces from the wormholes. After damage, the cortex cracks, and there are fewer insect passages in the xylem than with woodworm moths. The emergence holes of adults are mostly in the upper part and are in the form of a large round hole. The generation number of clouded beetles varies from place to place, and the overwintering state of the insects also varies. Generally, one generation occurs every two years, spanning three years. Adults or larvae overwinter in tree trunks and begin to be active in late April. May is the peak adult emergence period, and mid-to-late June is the peak egg-laying period. The larvae are light yellow and legless. The adults are dark brown or russet, with the habit of suspended animation and phototaxis.

The prevention and control method is to paint the trunk with Walnut Fruit Protectant No. I in winter or before the spawning period; use wire to clean the wood chips in the insect holes in places where there are insect holes, and then use a syringe to apply Walnut Fruit Protectant No. No. 1 original drug is injected into the worm hole and the hole is sealed with soil. The insecticidal effect is good; using the phototaxis and suspended animation habits of adult insects, lights are used to lure them to the tree for hunting at night. Observe leaves and twigs frequently during the day. If you find that small twigs are bitten and fresh, you can catch adult insects nearby. After the adults lay eggs, check regularly and find grooves for laying eggs. Use a hammer to knock the eggs and newly hatched larvae away. When the larvae burrow into the tree trunk, the insect droppings can be used as a sign. Use a thin wire to make a small hook at the tip, insert it through the insect hole, and kill the larvae with the hook.

6. Walnut leaf beetle

This insect mainly damages walnut branches and leaves and is one of the main pests of walnut leaves. Adults and larvae feed on the mesophyll, causing damage to the leaves in the form of nets or notches. Sometimes the entire leaf is eaten, leaving only the veins. This insect has one generation per year and overwinters as adults in the ground cover or in bark cracks at the base of tree trunks. The overwintering adults become active in early or mid-April of the following year, often clustering on leaves to feed and cause harm. They mate and lay eggs from late April to early May. The eggs are laid in lumps on the underside of leaves, with about 20-30 eggs in each lump. The larvae hatch out in mid-May. The newly hatched larvae feed in groups, and the damaged leaves turn yellow. After the second instar, they spread to the whole tree and cause damage. In late May, the tail end of the mature larvae adheres to the back of the leaf, peels off and pupates, and the end of the pupa's abdomen adheres to the larvae's molted skin, hanging upside down on the back of the leaf, and can bend and stretch when touched. The pupal stage lasts 4-5 days, and then emerges as an adult. After a short period of feeding, it descends the tree and lurks over the winter. May-June is the peak period when overwintering adults and larvae appear at the same time. When a large outbreak occurs, the leaves of the entire tree will be eaten up and appear to be on fire. If the plant is damaged for 2-3 consecutive years, the entire plant will die.

The prevention and control method is to combine the prevention and control of walnut fruit bugs in late April and early May, and use Walnut Fruit Balm diluted 800-1000 times for spray control; during the period when a large number of adults occur, use fire or black light to trap and kill them . Taking advantage of its habit of feigning death, it is artificially shaken down and killed.

7. Walnut branch blight

Symptoms

It mainly damages branches, especially 1 to 2-year-old branches.

The disease first invades the top shoots and then spreads downward to the branches and trunk. The branch cortex is dark gray-brown at first, then turns to light reddish-brown or dark gray, and many small black dots are formed in the diseased part, which are the conidia of the pathogenic bacteria. The leaves on the infected branches gradually turn yellow and then fall off. When the humidity is high, a large number of black short columnar conidia emerge from the conidia disk. If the humidity increases, oblong black spore masses are formed, containing a large number of spores.

Pathogen

Melanconium oblongum Berk. It is called Pansporium oblongata and belongs to the fungus Deuteromycetes. The conidiophores are buried under the epidermis of the host, and then break through the epidermis to be exposed; the conidiophores are densely grown on the conidiophores, unbranched, light gray or five-colored, and 25 to 50 (μm) in size; the conidia are borne At the top of the conidiophore, it is oval to elliptical in shape, mostly blunt at both ends, some with one end slightly pointed, single cell, size 16~27×8~13 (μm). The sexual form Melanconis juglandis (Ell.et Ev.) Groves, called walnut black shell, belongs to the Ascomycota fungus. The ascothecia are buried in the stroma, the ascospores are twin cells, and the septum is in the middle of the cell, light or colorless. The sexual stage is rare.

Transmission routes and disease conditions

The pathogenic bacteria mainly overwinter in the diseased parts of branches and trunks as conidial discs or mycelium. When conditions are suitable the following year, the conidia produced will survive the wind and rain. Or insects spread and invade from wounds. This fungus is a weak parasitic fungus, and walnut trees or branches with weakened growth are susceptible to the disease, and the disease is more severe in years of spring drought or frost damage.

Prevention and control methods

(1) Strengthen the management of walnut orchards, cut off diseased branches in time, bury them deeply or burn them to reduce the source of bacteria. Apply more organic fertilizer to enhance tree vigor and improve disease resistance.

(2) Pay attention to cold protection in the north to prevent the trees from freezing. Prevent and treat walnut tree pests promptly to avoid insect damage or other mechanical damage.

(3) If the main trunk is affected, the diseased part should be scraped off in time and disinfected with 1% copper sulfate or 40% thiramoscopyridine wettable powder 50 times

Then apply coal tar for protection.