How to control bagworm pests in bayberry cultivation

The male and female adults of the bayberry bagworm differ greatly in morphology. The male adult is 15-20 mm long with a wingspan of 30-35 mm, dark brown, with 3-5 semi-transparent markings near the outer margin of the forewings, and brown hindwings. The female adult is wingless, maggot-shaped, about 26 mm long, with a dirty white body, a fat abdomen and a slender tail end.

After the larvae grow up, males and females are also clearly different. The female larva is plump, reaching 25-40 mm in body length when grown, with a reddish-brown head, a grayish-yellow-brown thoracic dorsal plate and a blackish-brown abdomen; the male larva reaches 17-24 mm in body length when grown, with a yellowish-brown head and grayish-yellow-brown thorax and abdomen. The egg is oval and light yellow. The pupa is about 30 mm long and reddish-brown. The protective case is 40-60 mm long, with larger broken leaf pieces and a small amount of twigs attached outside the case, the twigs arranged irregularly. Life habits: In the middle and lower reaches of the Yangtze River, this insect has one generation a year, with occasional second-generation adults appearing between August and September, which also lay eggs and hatch, but their larvae often cannot overwinter. Generally, most overwinter as mature larvae hanging on branches in their protective cases. Pupation begins from late April to early May, and adults begin to emerge in early May. Adults mostly emerge around midnight; male moths are active after dusk and are phototactic. In mid-May female moths begin to lay eggs, depositing them in the pupal shell inside the protective case, with an average fecundity of about 2,600 eggs. Larvae begin to hatch in early June; newly hatched larvae chew the leaf mesophyll, leaving the epidermis, and eat little. After the 3rd to 4th instar, their appetite increases sharply and they devour large amounts of leaves. Damage is heaviest between August and September; the larvae can spin silk and hang from branches, drifting with the wind, hence the common name “hanged ghost”. The larvae are phototactic, and on osmanthus they mostly gather on branch tips and treetops to cause damage. After the larvae mature, they pupate inside the protective case and overwinter attached tightly to leaves with silk. Damage is generally severe in dry and hot summers, while in years with more rainfall, outbreaks are unlikely. Control methods: 1. In combination with pruning, remove the protective cases at any time. 2. Use black light lamps or sex pheromones to trap and kill male adults. 3. Protect natural enemies. Bagworm larvae are often parasitized by various natural enemies such as tumor ichneumon wasps, ichneumon wasps and tachinid flies, with parasitism rates reaching more than 50%. Therefore, use fewer broad-spectrum chemical pesticides and more highly specific microbial preparations, such as nuclear polyhedrosis virus preparations, Bacillus thuringiensis and Bacillus preparations, which not only have a high toxicity rate against the current generation of larvae but can also be passed on to the next generation and avoid pollution. 4. If the insect population density is high and the occurrence range is wide, you can choose 90% trichlorfon 1,000-fold dilution, 50% malathion emulsion 1,000-fold dilution, or 50% phosmet 800-fold dilution, all of which have good effects. As the larval age increases, the spray concentration should also increase; for example, trichlorfon should be used at 500-800-fold dilution. The spray volume should be large, and the protective case must be thoroughly wetted. The best time to spray is in the evening when the larvae are most active, followed by early morning. This insect has obvious repellency and strong starvation tolerance; after spraying certain control agents (including some microbial preparations), it refuses to feed, and its starvation tolerance can reach three weeks, so sometimes repeated spraying is needed to see results.