What are the control methods for the soybean yellow-bellied tiger moth?

The larvae of the yellow-bellied tiger moth, called caterpillars or leaf caterpillars, are a major seedling-stage pest of soybeans. At the same time, this pest can also damage corn, foxtail millet, sunflowers, vegetables, weeds and fruit trees.

1. Morphological characteristics: The adult yellow-bellied tiger moth is white, with many black spots scattered on the forewings. The abdomen and back are both yellow, with one black spot in the center of each segment and two black spots on each side; the legs have black stripes, and the femora are yellow. The eggs are hemispherical, creamy white when first laid, later turning grayish yellow; the larvae are earth-yellow on the back and ventral surface, with gray or grayish-brown longitudinal bands on the back and densely covered with long hairs from brownish yellow to dark brown; the prolegs are earth-yellow; the pupa is dark brown, relatively thick and short, and the earth-yellow cocoon is wrapped with a large amount of body hair shed by the larvae.

2. Life habits: The yellow-bellied tiger moth occurs in 1 generation per year in various regions, overwintering as pupae in cocoons and emerging as adults in early June of the following year. The adults hide by day and come out at night, hiding in crops or grass during the day and becoming active at night, and they are phototactic. About 3 to 4 days after emergence, the adults begin to mate and then lay eggs on the underside of the middle leaves of the crops, and the eggs hatch into larvae after 5 to 6 days. The first-generation larvae occur in mid-to-late June, and the newly hatched larvae feed in groups. After growing slightly larger, they disperse to cause damage. The larvae have a habit of playing dead and are good at crawling; those of the 3rd to 4th instar can crawl 5 to 7 m per minute, and those of the 6th to 7th instar can crawl 10 to 14 m per minute. After being disturbed, the pest immediately burrows into soil cracks or hides under grass.

3. Damage symptoms: The yellow-bellied tiger moth damages crop leaves as larvae, and can feed both day and night, stopping feeding for only 1 to 2 hours during the hot midday, and feeding most in the early morning, evening and at night. Generally, the larvae begin to gnaw on the leaf mesophyll 40 to 50 minutes after hatching, and after the 5th instar their food intake increases sharply; they can eat the leaves into notches or holes, causing the leaf surface to show withered yellow spots, and in severe cases they eat the leaves completely, and even the young stems are all eaten, after which they move to nearby soybean fields to continue causing damage. One larva can eat 28 to 37 soybean leaves in its lifetime, and when it occurs severely it can cause total crop destruction.

4. Control methods: When controlling, pay attention to timely chemical control at the young larval stage; when the larvae are too old, the control effect is poor; spray pesticides in the early morning and evening when the larvae are most active; and carry out coordinated control, because the pest crawls quickly, and only when all households spray pesticides at the same time can they prevent it from moving and achieve a better control effect. Specific methods: (1) Install black light traps to kill adults. Because the adult yellow-bellied tiger moth is phototactic, black lights can be installed to trap and kill adults, thereby reducing the number of eggs laid by adults. (2) Carry out deep autumn plowing to destroy the overwintering sites of the yellow-bellied tiger moth and reduce the source of the pest. (3) Promptly clear weeds around the damaged field, or dig trenches to prevent movement. When larvae are found migrating into the main field, trenches can be dug around the field and some pesticide scattered in the trenches to kill the larvae. (4) Chemical control. When it occurs, spray 2.5% trichlorfon powder or 5% carbaryl powder. Use 22.5 to 30 kg per hectare; a 50% phoxim emulsifiable concentrate 800 to 1000 times solution can also be sprayed. When the larvae are older, a 90% crystallized trichlorfon 1000 to 1500 times solution can be sprayed, using 375 to 450 kg of solution per hectare.