Beijing Battling Fall Webworm Infestation with Unprecedented Measures

In Beijing, China, an unusually high number of fall webworm caterpillars have been spotted in recent weeks. According to reports, over 70,000 of these invasive moths were collected by visitors at the Beijing Wildlife Park in a two-day contest.

The fall webworm is native to North America and has been introduced to China as an invasive species. They live in groups, spin silken webs around leaves and branches, and feed on over 300 plant species, causing damage to trees, fruit plants, flowers, and crops.

The outbreak of fall webworms in Beijing can be attributed to several factors. Warmer winters have increased the survival rate of the moths' pupae, with a recorded survival rate of 84.2% this year compared to 65.3% in 2023. Frequent summer rainfall has also reduced suitable windows for spraying and may wash pesticides off foliage.

Beijing is using multiple control methods to combat the infestation, including removing webbed branches, trapping mature larvae, and applying targeted pesticides. Biological control is another tool being employed, with nearly 700 million Chouioia cunea parasitoid wasps released in the city so far this year.