What kind of pest is the Northeast giant black chafer?
〔Pest scientific name〕Holotrichia diomphalia Bates
〔Damaged crops〕It damages sugar beets and various vegetables, and also damages legume and grass-family crops.
〔Pest identification〕The larvae cause damage by biting through the roots and stems of vegetable seedlings, causing the whole plant to wither and die, resulting in missing plants and broken rows; they also gnaw on root tubers and stem tubers, affecting quality. The adults feed on crop leaves, especially preferring crops such as soybean and peanut, leaving holes or notches. The Northeast giant black chafer belongs to Coleoptera, Scarabaeidae. The adult body is 16-21 mm long and 8-11 mm wide, black or dark brown, glossy. The antennae are yellowish brown. The sides of the pronotum are arcuate. The scutellum is nearly semicircular. The elytra are long oval, each elytron with 4 longitudinal ribs. The outer side of the fore tibia has 3 teeth, and the inner side has 1 spur. The egg is about 2.5 mm long, white, long oval when newly laid, and round later. The larva is a white grub. When the larva is mature, the body is 35-45 mm long, the head is yellowish brown, the body is milky white, and it curls into an "O" shape when at rest. There are 3 setae on each side of the anterior vertex of the head, arranged in 1 longitudinal row. The anus has no bristle row. The pupa is 21-23 mm long, yellow or yellowish brown, the caudal segment is narrowly triangular, the upper elytra, and the end has 1 pair of forked tail spines (Figure 36).
〔Life habits〕The Northeast giant black chafer has 1 generation every 2 years, and adults and larvae overwinter alternately in alternate years. Adults are first seen from late April to early May, the mass emergence period is from May to June, the peak egg-laying period is in mid and late June, the peak egg hatching period is in mid-July, and in mid and late October the larvae burrow below the frozen soil layer to overwinter. The overwintering larvae rise to the surface soil layer in early and mid May of the second year, and the severe damage period is from late May to early June. From July to September, mature larvae enter the soil to make cells and pupate, and after about 20 days they emerge as adults, which do not come out of the soil that year and overwinter in the soil cells. They do not begin to emerge until late April of the second year. During the day, adults hide in the soil, and after dusk they emerge to feed and move about. Adults have the habit of playing dead, and males are strongly phototactic and attracted to undecomposed manure. Adults mostly mate in the evening and lay eggs after 10-15 days. Adults prefer to feed on the leaves of crops such as soybean and peanut, and mostly lay eggs in the soil of these fields. Each female lays an average of more than 100 eggs in her lifetime. The developmental duration of this pest: egg stage 15-22 days; larval stage 340-400 days; pupal stage about 20 days; adult stage about 300 days. Soil temperature and humidity have a direct effect on white grub activity. When the soil temperature at 10 cm depth is 22-23°C, they mostly activity at 10-20 cm depth; if it is 5-10°C, they move downward. The optimum humidity is 15%-20%.
〔Control measures〕(1) Plowing and turning the soil. After harvesting crops in autumn, autumn plowing should be carried out in time, which can freeze overwintering adults and larvae to death or allow them to be eaten by birds. (2) Apply fully decomposed manure to reduce white grub damage. (3) Manual control. In spring, collect insects manually along with plowing to reduce the insect population. After vegetables are planted, if white grub damage is found in the field, check plant by plant and kill them. (4) Control adults. During the peak adult occurrence period, spray with 50% phoxim emulsifiable concentrate, or 90% trichlorfon crystal at 800-1000 times dilution, or 25% quinalphos emulsifiable concentrate at 1500 times dilution, or 40% dimethoate emulsifiable concentrate at 1000 times dilution, or 2.5% deltamethrin emulsifiable concentrate at 3000 times dilution. (5) Control larvae. Apply poisoned soil: use 50% phoxim emulsifiable concentrate, or 90% trichlorfon, or 25% fonofos microcapsule suspension, with 1.5-2.25 kg of pesticide per hectare, diluted with a small amount of water, then mixed with 225-300 kg of fine soil, and apply in the planting holes. Cover the poisoned soil with a layer of soil so that the seedlings are separated from the poisoned soil to avoid phytotoxicity. Root drenching: in plots with a relatively large larval population, the above pesticides can also be used for root drenching.