What Are the Main Insect Pests on Chestnut Trees? Read This One Article to Understand
What are the main insect pests of chestnut? Please introduce them. The occurrence characteristics and control methods of the chestnut gall wasp and the cloud-spotted longhorn beetle on chestnut trees are introduced as follows: 1. Chestnut gall wasp 1. Morphological characteristics The adult is a small black wasp, body length 2-3 mm, with transparent forewings and hindwings. The egg is oval, length 0.1-0.2 mm, milky white, with a short filamentous stalk at the tail end...
What are the main insect pests of chestnut? Please introduce them.
The occurrence characteristics and control methods of the chestnut gall wasp and the cloud-spotted longhorn beetle on chestnut trees are introduced as follows:
I. Chestnut gall wasp
1. Morphological characteristics
The adult is a small black wasp, body length 2-3 mm, with transparent forewings and hindwings. The egg is oval, length 0.1-0.2 mm, milky white, with a short filamentous stalk at the tail end. The larva is 2-3 mm long, spindle-shaped, stout, legless. Both ends of the body are slightly pointed, milky white, with brown mouthparts. The pupa is a naked pupa, body length 2.5-3 mm, initially milky white, black at eclosion, with red compound eyes.
2. Habits and damage characteristics
The chestnut gall wasp has one generation per year and overwinters as first-instar larvae in damaged chestnut buds. From mid-to-late March to early April of the following year, during the budburst period of chestnut, the larvae begin activity, and the damaged buds gradually swell to form galls. The galls are round or irregularly oval, hard, cherry red, sometimes with green, and sometimes small deformed leaflets grow on the galls, seriously affecting flowering, leafing, and shoot growth of chestnut trees. The insect begins pupation in early May, and a large number of adults emerge in mid-June. After emergence, the adults stay in the gall for 10-15 days, then bite a hole and bore out, laying eggs in plump buds, generally 2-3 eggs per bud. Adults mostly emerge from the galls and are active during the day, most frequently from 8-12 a.m.; clear, windless weather is favorable for adult emergence and activity. Their flying ability is not strong, and they spend most of their time crawling on the tree. From late July to mid-September, larvae hatch, feed and cause damage inside the buds, and form small chambers, then begin overwintering in late September.
3. Control methods
Before the end of May, remove gall-bearing branches. From April to May, before adult emergence, in combination with pruning, cut off all the branches and leaves with galls of the current year and take them out of the orchard to burn, so as to prevent the chestnut gall wasps in the galls from emerging and reproducing. If this measure is carried out thoroughly and throughout the chestnut-growing area, the damage can be eliminated. For heavily damaged trees, carry out heavy pruning and strengthen fertilizer and water management to enhance tree vigor.
From June to July, during the adult occurrence period, spray the canopy. If the previous measure was not carried out thoroughly, then use spraying as a remedy. During the peak activity period of chestnut gall wasps emerging from galls (generally from mid-June to early July), spray 50% fenitrothion 800-1000 times dilution or 80% dichlorvos 800-1000 times dilution or 90% trichlorfon crystal 800-1000 times dilution. Spray the canopy twice on clear mornings, with the first spray in mid-June and another spray 10-15 days later. The chestnut gall wasp has parasitic natural enemies, so try not to use the method of spraying on the tree foliage.
II. Cloud-spotted longhorn beetle
1. Morphological characteristics
The adult body length is 32-97 mm, black or dark brown, with 2 kidney-shaped white spots on the pronotum, and 2-3 rows of cloud-like white spots of varying sizes on the elytra. The egg is long oval, pale yellow, about 8-9 mm long. The larva is 70-80 mm long, milky white or pale yellow, with a "mountain"-shaped brown patch on the pronotum. The pupa is 40-70 mm long, milky white to pale yellow.
2. Habits and damage characteristics
The cloud-spotted longhorn beetle has one generation every two years and overwinters as adults or larvae inside the trunk. Adults appear from April to June, feed on leaves and tender branches, and begin mating and laying eggs about 30-40 days after feeding. Adults have weak flying ability and are prone to falling to the ground and crawling when disturbed; during the adult occurrence period, this habit can be used to shake the tree and kill them. Adults mostly lay eggs on trunks within 2 m above the ground. When laying eggs, they first bite a soybean-sized groove in the bark, then lay 1 egg in the groove. After the larvae hatch, they first bore triangular feeding marks under the bark and discharge a large amount of frass from the entry hole, and the bark gradually swells and splits longitudinally. After the larvae have caused damage inside the bark for a period, they bore into the xylem, and upon reaching the pith, they bore upward along the trunk. In severe cases, the whole tree is hollowed out and dies. In August of the second year, they pupate in the larval gallery, and in September they emerge as adults, then in April-June of the third year they bite a round hole and bore out of the trunk.
3. Control methods
(1) Manual control
The main work is to manually scrape off eggs and newly hatched larvae. The egg-laying sites of the cloud-spotted longhorn beetle are relatively low, and the egg-laying marks and damage symptoms of newly hatched larvae are obvious. From May to July, during the adult egg-laying and larval hatching period, inspect frequently. When egg-laying marks and damage symptoms of newly hatched larvae are found on the trunk, scrape them off promptly with a sharp knife and apply 40% omethoate 10 times dilution to kill the larvae during the early stage of damage under the bark. This method is fast and effective and is a very important control measure.
(2) Applying pesticide to insect holes
After April, inspect the trunk frequently. If fresh frass of cloud-spotted longhorn beetle larvae is found on the trunk, promptly remove the frass from the insect hole and hook-kill with a steel wire, or insert a cotton ball dipped in undiluted dichlorvos or gasoline into the insect hole for fumigation, and seal the insect hole with wet mud after applying the pesticide.
(3) Whitewashing the trunk
In late April, before adults lay eggs, use a whitewash made of 10 kg quicklime, 1 kg sulfur, 50 g salt, and 20 kg water to brush the trunk below 2 m to prevent adult egg-laying damage.
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