Beijing fights invasive moths with parasitic wasps and caterpillar-catching contests

Beijing is battling an invasive pest known as the North American fall webworm using an unusual strategy - releasing over a billion parasitic wasps and organizing caterpillar-catching contests. The caterpillars, the larval stage of Hyphantria cunea, have coated trees in the city and surrounding areas with grayish-white webs as they devour foliage. Although harmless to humans, these insects pose a threat to numerous plant species, according to China Science Daily.

Professor Chen Min from Beijing Forestry University reported that this generation of caterpillars faces a higher risk of spreading than usual, making control measures more challenging. He attributed this to a warm winter and a rainy summer, which create ideal conditions for the pest to thrive, washing away pesticides.

To combat the outbreak, municipal workers employ physical measures such as removing webs and trapping moths, along with spraying pesticides. Nearly 3,000 monitoring sites have been set up around Beijing to guide control efforts, reported Xinhua, the state news agency. Community efforts include caterpillar-catching competitions and encouraging people to report infected trees.

The fall webworm, native to North America, was accidentally introduced to Europe in the 1940s and has since spread to Asia. In China, it was first detected in 1979 and has now been found in 13 provincial-level areas. In the US, native populations are typically kept under control due to natural predators.

Chen noted that this year's concentrated outbreak, the third generation, poses a significant challenge. The first generation, which emerges around May, is the most crucial to target. This year's outbreak in China highlights the need for better synchronization and adaptation in control efforts, especially as climate change expands the pest's suitable habitats.