The life history and control methods of several forest pests, including the larch cone fly, gypsy moth, and others, are described in detail. These pests have specific biological characteristics that influence their behavior, development, and impact on forest ecosystems.
**2. Living Habits**
(1) **Adults**: Male adults typically emerge 2–3 days earlier than females. Newly emerged adults are active on the ground, with females being chased by males for mating. Copulation usually occurs on the ground, grass, shrubs, or dead branches, sometimes on saplings or tree branches. Mating happens mainly between 10:00 and 12:00. After mating, females climb trees to lay eggs at the tip of outer leaves, 1–3 mm below the tip. Each female produces 26–32 eggs, and adults may feed on young leaves as supplementary nutrition. Their lifespan is 3–11 days, with a male-to-female ratio of 1:0.9. Adults are most active between 9:00 and 16:00, rarely active after rain or cloudy days. They can migrate up to 1 km via wind.
(2) **Eggs**: Hatching occurs between 6:00 and 9:00, accounting for over 60% of daily hatching. The hatching rate is about 90%, and the egg period lasts 20–30 days.
(3) **Larvae**: Immediately after hatching, larvae climb to the leaves to build nests. They start feeding every other day, with small initial food intake and difficulty in detecting fecal droppings. Mortality among 1st and 2nd instar larvae reaches up to 20%. By the 4th instar, larvae feed heavily during the day and forage at night. They molt five times and take 21–28 days to develop. The development of all instars (1st to 5th) is visible simultaneously. Five days after dropping from the tree, larvae create underground chambers.
(4) **Pupae**: Pupation occurs in earthen chambers 2–3 cm deep, typically near the base of the trunk. The pre-pupation period averages 295 days, with a pupation rate of 85%.
(5) **Control Methods**
(1) **Artificial Control**: In late autumn and early winter, soil is turned over in Laoshan Mountain to destroy overwintering sites, exposing pre-cockroaches to freezing or predation. In 1992, this method was used to control a large infestation in Taozi Forest Park, effectively reducing the worm population.
(2) **Biological Control**: Natural enemies such as birds and nematodes are protected and utilized. Red tree ants were introduced to prey on larvae, achieving long-term pest control.
(3) **Chemical Control**: Insecticides like 4.5% cypermethrin EC are sprayed before egg hatching or before the 4th instar. Smoke machines are used to apply the solution, achieving over 92% effectiveness under favorable conditions.
(4) **Pollution-Free Prevention**: Plant-based insecticides like 1.2% bitter-smoke EC mixed with diesel are used to control larvae, with a success rate exceeding 90%.
**5. Coleophora sinensis Yang**
This species belongs to the family Coleophoridae. It is distributed in parts of Shanxi and Hebei. Adults have a body length of 2.5–3 mm and a wingspan of 6.5–8.5 mm. They exhibit dark gray coloration with a silken sheen. Larvae overwinter on branches and bark, beginning feeding in late April. High larval density causes entire canopies to appear pale. Eggs are laid on the back of leaves, with one egg per instance.
**6. Gypsy Moth (Lymantria dispar Linnaeus)**
This species is classified under the family Noctuidae. It is found in China and abroad, feeding on over 500 plant species. Adults are brown with distinctive markings, and females are larger. Eggs are oval, yellow initially, turning brown later. Larvae go through six instars, with mature larvae forming shelters. Control measures include forest management, manual removal, light trapping, chemical sprays, and biological agents like viruses and parasitoids.
**7. Larch Cone Fly (Strobilomyia laricicola)**
This fly is found in regions such as Heilongjiang, Jilin, and Xinjiang. Adults are gray, with dark brown wings. Eggs are needle-shaped, and larvae feed inside cones. Control includes physical traps, chemical injections, and monitoring based on environmental conditions.
These pests require integrated management strategies, combining cultural, biological, and chemical controls to ensure effective and sustainable pest management in forest ecosystems.
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