Charcoal production and control of Rhododendron crenatum

Stephanitisscott. Belongs to Hemiptera Pentatomidae, which is widely distributed and is the main pest of rhododendron flowers. The host plants are rhododendron and horse drunken wood, which seriously affected the growth, reproduction and ornamental value of the two genera of flowers.

1. Harmful symptoms

The rhododendron crown bug mainly harms the leaves of the host plant by nymphs and adults, absorbs juice and excretes feces, which makes the back of the leaves yellowish yellow, and needle-like white spots appear on the front of the leaves, which seriously make the whole leaves green and pale, affecting plant photosynthesis, slow plant growth and early defoliation, reducing the ornamental value.

2 morphological characteristics

The adult body is small and flat, about 3.4mm, about 2.0mm wide, the head is small, brown, the compound eye is large and protruding; the antennae are 4, and the third is the longest; the forechest dorsal plate is well developed, with reticulate lines, extending forward to cover the head, backward extending to cover the small shield, and protruding from both sides of the thin disc-shaped lateral dorsal piece; the wing membrane is transparent, the wing vein is dark brown, the front wing is covered with reticulate pattern, and the joint between the two front wings shows an obvious "X" pattern. The abdomen of the female is complete and spindle-shaped, while the abdomen of the male is small and long oval. The egg is milky white, about 0.52mm long, about 0.18mm wide, banana-shaped, bag mouth-shaped at the top and slightly curved at the end. The nymph is 5 years old, the mature nymph is flattened, about 1.96mm in length and 0.95mm in width, the forechest is well developed, the wing bud is obvious, the body is dark brown, and the compound eye is red. There are thorn-like processes in the head, chest and abdomen, 3 at the top of the head, arranged in an isosceles triangle, 1 beside the compound eye, 2 pairs on the chest and back, and 1 on the back of the 2nd, 4th, 5th and 7th segments of the abdomen.

3 occurrence regularity

The adults and nymphs overwintered in litter, weeds or rhizosphere topsoil. If the climate is warm, the overwintering phenomenon is not obvious, and its harm can be seen almost all the year round. The overwintering adults and nymphs begin to move in late March every year, and the first generation nymphs appear in the middle of April, with the largest number and the most serious damage from June to September. The egg stage is 7-15 days, the nymph stage is 16-23 days, and the average duration of one generation is 28-30 days. The newly hatched and molted nymphs were snow-white all over, and then the color of the nymphs gradually deepened. The nymphs are highly clustered and often cluster near the main and lateral veins of the back of the leaves. The adults are pink and white at Eclosion and gradually turn dark brown after 2 hours. They are not good at flying and can mate and lay eggs 2 days after Eclosion. The eggs are mostly laid in the leaf tissue next to the dorsal main vein of the host leaf, and a few are produced on the marginal vein and the main vein, covered with brown gelatinous material. High temperature and dry weather are the most suitable for the occurrence of the insect.

4 methods of prevention and control

4.1 artificial hunting and killing

Because of its clustering and non-toxicity to the human body, when a small number of pests occur on potted cuckoos, they can be pinched and killed with their hands.

4.2 Landscape measures

The litter and weeds in the nursery are all latent places for overwintering. Clearing fallen leaves and weeding in time at the end of autumn can eliminate a large number of overwintering insect sources, and the selection of pest-free seedlings can also reduce the occurrence of pests.

4.3 Chemical control

When the occurrence of insect pests is serious, chemical control is a rapid and effective method. It can be sprayed with 1000 times of 10% cypermethrin EC or 40% omethoate EC or 2000 times of 50% fenitrothion EC, 2.5% kungfu EC 2500 × 3000 times, and 10% imidacloprid wettable powder 1500 times.

4.4 Protection and utilization of natural enemies

The natural enemies of rhododendron crown net bugs are lacewings, spiders, ants, etc., and lacewings are the dominant species. There are 4 and 5 lacewings on a potted rhododendron, which can reduce the population density of insects and do not need to be controlled. Therefore, when pests occur, we should pay attention to investigate the species and number of predators. If we find predatory natural enemies such as lacewings, we should use or not use pesticides to protect natural enemies and control the occurrence of insect pests.