Pest Control Methods in Chestnut Cultivation

1. Chestnut gall wasp

The chestnut gall wasp, also called the chestnut gall wasp, has a dark brown head and abdomen in the adult stage, filiform brown antennae, and a swollen, jet-black thorax. It lays eggs in the buds from June to July, and the larvae grow and overwinter inside the buds. In spring, when the buds sprout and produce short shoots, the damaged branches or leaf stalks swell into galls (tumors), causing the branches and leaves to die and the tree to weaken, seriously affecting growth and fruiting in the current and following year.

Control methods: ① In winter, prune out weak twigs and diseased or pest-infested branches and burn them to eliminate overwintering larvae. ② Protect the natural enemy, the encyrtid wasp. ③ Before and after adult emergence from the galls (June to July), spray 40% omethoate 1000x solution; or in early April (when chestnut buds are red and swollen but not yet open), apply 40% enhanced omethoate to the trunk and branches. You may select a branch or trunk about 10 cm thick, scrape off the cork layer in a 30 cm long semicircular ring, and brush on about 10 mL of the solution.

2. Cloud-banded longhorn beetle

The adult cloud-banded longhorn beetle is dark brown, with 2 white spots on the pronotum, and the larva has a brown “mountain”-shaped mark on the pronotum. It mainly damages branches and trunks, causing dead branches and affecting tree vigor.

Control methods: ① From May to July, capture and kill adults before egg laying. ② From June to July, scrape off eggs and newly hatched larvae from the trunk. ③ Use a steel wire hook to kill larvae that have already bored into the trunk. ④ Inject 80% dichlorvos 100x solution into the insect holes, or use a cotton ball soaked with 50% phosphamidon (or 50% fenitrothion) 40x solution and plug the insect holes.

3. Red-waisted clearwing moth

The adult red-waisted clearwing moth resembles a large yellow-jacket wasp in body color. The female adult has a yellow abdomen, a red-purple waist, membranous transparent wings, and brown hair tufts on the legs, with a spindle-shaped cocoon on the outside made of silk, frass, and wood shavings. The larvae overwinter under the bark of branches and trunks, begin activity in April of the following year, and adults emerge in peak numbers from late August to late September. They lay eggs in cracks in the rough bark of the trunk or in insect tunnels, mostly on the trunk 10-70 cm above the ground. They mainly damage the phloem of the trunk and main branches. The damaged areas bulge like tumors, the bark splits and curls, and the scars do not heal for a long time. In severe cases, the tree dies.

Control methods: ① During the peak adult period, spray the trunk with 80% dichlorvos 1000x solution to kill adults and newly hatched larvae. ② Find areas with insect frass and scrape out the larvae. ③ Apply 1 part 80% dichlorvos plus 30 parts kerosene to the trunk.

4. Chestnut weevil

The adult chestnut weevil is small, black or dark brown, 7-9 mm long, with a slender snout. The larva is spindle-shaped and milky white. The larvae feed on the kernel. About 10 days after harvest, the larvae mature, bore out of the chestnut fruit, and make cocoons to overwinter.

Control methods: ① During the adult activity period, spray the canopy with 90% trichlorfon or 80% dichlorvos 1000x solution. ② Fumigate the chestnut fruits. Under sealed conditions, fumigate with 2.5-3.5 g methyl bromide per cubic meter of chestnut fruits for 24-48 hours, or treat with 30 mL carbon disulfide for 20 hours to kill the pests without affecting germination ability. ③ Kill larvae by soaking chestnut fruits in warm or hot water. Soak in warm water at 50-55°C for 15-30 minutes, or in hot water at 90°C for 10-30 seconds. The insect mortality rate can reach over 90%, and germination ability is not affected.

5. Peach fruit borer

The peach fruit borer is also called the peach fruit moth, fruit-spot pyralid moth, etc. The adult is bright yellow, with rows of black spots on the back and sides of the abdomen. The larvae overwinter in bark cracks or in dry involucres and similar places. After adults emerge, they lay eggs on the involucre around August. After hatching, the larvae enter through the stalk of the involucre and often cause severe fruit drop. During chestnut growth, only a few older larvae bore into the chestnut fruits, but after harvest they feed heavily, often hollowing out the chestnut fruits and binding them together with frass and silk-like material, causing even non-hollowed chestnut fruits to lose their food value.

Control methods: ① During the larval hatching period, spray 80% dichlorvos 1000x solution. ② After the involucres are brought back, remove the shells and take out the chestnut fruits promptly within 5-6 days to reduce damage. ③ After harvest, fumigate the involucres with carbon disulfide, or quickly dip the involucres in 90% trichlorfon 100x solution and then pile them up.

6. Chestnut red spider mite

The chestnut red spider mite damages the leaf surface with adults and nymphs, causing the affected leaves to show pale small spots, and finally turn yellow-brown, scorched, and drop early. It overwinters as eggs on the backs of branches, hatches from late April to mid-May, and the peak occurrence period is from mid-May to early July.

Control methods: ① During the occurrence period, spray the canopy with dicofol 800-1000x solution, or 40% dimethoate 1000x solution. ② In early to mid-May, apply chemicals to the trunk. Scrape a 10 cm ring at the base of the trunk (only scrape off the rough bark, slightly exposing the tender bark), apply 40% dimethoate 1-10x solution or 50% monocrotophos 1-20x solution, apply once more after the solution dries slightly, and wrap with plastic film after it dries.

7. Red-legged green chafer

The red-legged green chafer is also called the copper green chafer. Adults damage young leaves, young shoots, and inflorescences, often eating leaves into a net-like pattern. Larvae bite the root system, causing the tree to weaken or even die. The larvae overwinter in the soil, emerge from late April to early May, and the adult peak period is from June to July.

Control methods: ① Poison the larvae. Evenly broadcast 3% carbofuran at 1-1.5 kg per mu, then rake the soil to cover it, or drench with 50% phoxim 1000x solution. ② During the adult peak period, spray 90% trichlorfon 1500x solution or 80% dichlorvos 1000x solution in the evening. ③ In the morning or evening, shake the insects down by hand and kill them. ④ Use lights at night to trap and kill them.

8. Great bagworm

The larvae of the great bagworm hide in bags, stand on the leaf surface or hang on the underside of leaves, and eat leaves. They are highly voracious and often eat all the leaves on the tree.

Control methods: ① Spray the canopy with 90% trichlorfon 800-1500x solution. ② Remove the insect bags.