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What are the characteristics of the black locust seed chalcid, and how can it be controlled?

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The black locust seed chalcid mainly damages black locust (Robinia pseudoacacia). Its larvae feed on the seeds inside the pods. Adult: body length about 3 mm, black, antennae yellowish-brown, thorax raised, wings transparent, covered with short spines, wing venation simple, slightly yellow. Egg: spindle-shaped, with a long slender stalk at one end. Larva: mature body length about 4 mm, milky white, head inconspicuous, mandibles brown, body curved. The black locust seed chalcid has 2 generations per year. It overwinters as a larva inside the seed. In the following year it generally pupates between April and May, and adults emerge and lay eggs after early to mid-May

The black locust seed chalcid mainly damages black locust (Robinia pseudoacacia). Its larvae feed on the seeds inside the pods.

Adult: body length about 3 mm, black, antennae yellowish-brown, thorax raised, wings transparent, covered with short spines, wing venation simple, slightly yellow. Egg: spindle-shaped, with a long slender stalk at one end. Larva: mature body length about 4 mm, milky white, head inconspicuous, mandibles brown, body curved. The black locust seed chalcid has 2 generations per year. It overwinters as a larva inside the seed. In the following year it generally pupates between April and May, and adults emerge and lay eggs after early to mid-May; in mid-May the first-generation larvae hatch and bore into the pods to feed on the seeds, and in mid-June the second-generation larvae appear, boring and feeding on the seeds inside the pods until autumn, then overwintering inside the seeds.

The occurrence period of this insect varies slightly from year to year, but it is consistent with the phenological period of black locust, especially the pod formation period. Adults lay eggs inside the seeds, and after egg laying yellow gum spots can be seen on the surface of the pods; after the larvae hatch they bore into and feed on the seed cotyledons, and the damaged pods gradually change color and develop brown spots. The larvae do not move to other seeds; in their lifetime they damage only 1 seed, and the surface of the damaged seed appears pale purplish-brown.

Control methods. Strengthen quarantine, strictly prohibit the spread of seeds carrying the insect, and when necessary fumigate the seeds; before sowing, soak the seeds in 80°C warm water for 30 minutes to kill the larvae in them; for large areas of forest, during the adult occurrence period, dichlorvos smoke-generating cartridges with inserted tubes can be released for fumigation; in winter, thoroughly remove the insect-infested pods from the trees to kill the overwintering larvae.

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