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Occurrence Patterns and Control Methods of the Soybean Hawkmoth

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Damage symptoms: The soybean hawkmoth feeds on leaves as larvae. Young larvae eat leaves into a net-like, notched pattern, and after the third instar the larvae can eat all the soybean leaves, preventing the plants from setting pods and greatly affecting yield. Occurrence patterns: Mid-to-late July to early August is the peak period for adult egg-laying, late July to late August is the peak period of larval damage, and in early September the light-yellow mature larvae enter the soil to overwinter. Life habits: Adults: Adults hide by day and come out at night, and have a strong tendency toward black light lamps. They begin activity in the evening and are strong fliers with strong migratory ability. They mate at night, and lay eggs 3 days after mating. Eggs are mostly scattered on the undersides of soybean leaves, generally 1 to 2 eggs per leaf, and the eggs hatch into larvae after about 7 days. Larvae: Larvae are photophobic, mostly staying on the undersides of leaves or on stems during the day, and feeding strongly at night; on cloudy days they can feed all day. First and second instar larvae eat little and generally do not move between plants to cause damage; after the fourth instar they have the habit of moving to cause damage; fifth instar larvae show a sharp increase in food intake, accounting for about 90% or more of the total food consumption. The larval stage lasts 30 to 35 days.

Damage symptoms: The soybean hawkmoth feeds on leaves as larvae. Young larvae eat leaves into a net-like, notched pattern, and after the third instar the larvae can eat all the soybean leaves, preventing the plants from setting pods and greatly affecting yield.

Occurrence patterns: Mid-to-late July to early August is the peak period for adult egg-laying, late July to late August is the peak period of larval damage, and in early September the light-yellow mature larvae enter the soil to overwinter.

Life habits: Adults: Adults hide by day and come out at night, and have a strong tendency toward black light lamps. They begin activity in the evening and are strong fliers with strong migratory ability. They mate at night, and lay eggs 3 days after mating. Eggs are mostly scattered on the undersides of soybean leaves, generally 1 to 2 eggs per leaf, and the eggs hatch into larvae after about 7 days. Larvae: Larvae are photophobic, mostly staying on the undersides of leaves or on stems during the day, and feeding strongly at night; on cloudy days they can feed all day. First and second instar larvae eat little and generally do not move between plants to cause damage; after the fourth instar they have the habit of moving to cause damage; fifth instar larvae show a sharp increase in food intake, accounting for about 90% or more of the total food consumption. The larval stage lasts 30 to 35 days.

Occurrence conditions: Drought is unfavorable to the occurrence of the soybean hawkmoth. Dense plant growth, low-lying terrain, and fertile silty soil make occurrence more severe; early-maturing soybean varieties suffer more severe damage. During pupation and emergence, if rainfall is moderate, occurrence will be severe. If there is too much rain, the occurrence period is delayed.

Control methods: Trapping and killing adults: Taking advantage of the adults' strong phototaxis, set up black light lamps to trap and kill adults, which can reduce the number of eggs laid in soybean fields and lessen the damage. Chemical control: The proper timing for controlling soybean hawkmoth larvae should be before the third instar. Use 4.5% beta-cypermethrin at 1500 to 2000 times dilution per mu, or 50% phoxim emulsifiable concentrate at 1500 times dilution for spraying, with 50 kg of spray solution per mu. Because the larvae have the habit of hiding by day and coming out at night, spraying should be done after 5 p.m.

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