At 10 a.m. on the 22nd, at the summit of Gyeyang Mountain in Gyeyang-gu, Incheon. People holding long hoses headed into the brush beside the trail. When someone shouted, "Start the engine!" a powerful stream of water burst from the end of the sprayer moments later.
The water spreading like white mist through the wet soil and piles of fallen leaves contained an eco-friendly control agent to kill the larvae of the red back hairy fly, known as the lovebug. After Gyeyang Mountain suffered from swarms of lovebugs last summer, a preemptive control experiment began there this year.
◇Pesticide with a 98% kill rate… dissolves larvae's gut before pupation
That day, researchers from the Ministry of Climate, Energy and Environment National Institute of Biological Resources and the Sahmyook University Institute of Environmental Ecology sprayed BTI (Bacillus thuringiensis israelensis) control agent across nine sites totaling 900㎡ (about 272 pyeong) around the summit of Gyeyang Mountain. They mixed about 2 kg of the agent with 1 ton (t) of water and sprayed mainly on leaf litter, brush, and moist soil. The work continued from morning to afternoon.
Kim Dong-geon, head of the Sahmyook University Institute of Environmental Ecology who led the development of the BTI agent, said, "A pair of lovebugs lays up to 500 eggs," and noted, "They prefer high, humid places in the mountains, so we are spraying BTI to control their numbers."
Lovebug larvae usually pupate around mid-May and emerge as adults from late June. At this time of year, the larvae hide and grow under fallen leaves and in moist soil. Even at the site that day, one had to look closely at the ground to find the larvae. They were about 1 cm long, small and similar in color to twigs, making them hard to distinguish with the naked eye.
The BTI agent developed by the research team is an eco-friendly microbial product using soil bacteria that works by acting only on the guts of specific insect larvae to kill them. It is said to have little impact on plants or the surrounding ecosystem. In an indoor verification test in Oct. last year, the larval kill rate within 48 hours after application was 98%.
Next month, the team plans to install 10 traps each in treated and untreated areas to verify actual population reduction effects and safety. They will then proceed with the biocidal product registration process. Additional control work and regular inspections will continue through July, when lovebug numbers surge.
◇Lovebugs spread from Incheon to Seoul… complaints "frequent"
They will also expand the test sites. The research team plans to conduct on-site verification next month around Baengnyeon Mountain in Eunpyeong-gu and Bulam Mountain in Nowon-gu, Seoul. Park Seon-jae, a researcher at the National Institute of Biological Resources, said, "The goal is not to eradicate lovebugs completely, but to guide ecological stabilization by controlling an excessively increased population."
In Korea, lovebugs were first discovered on Gyeyang Mountain in 2015. Since 2022, they have been appearing in large numbers, mainly in the northwestern Seoul metropolitan area, including Eunpyeong-gu in Seoul and Goyang in Gyeonggi Province. Their numbers are increasing rapidly every year.
Lovebugs are classified as beneficial insects because their larvae decompose fallen leaves and organic matter, and adults carry pollen. But because males and females fly attached in swarms and stick to light-colored clothing or people's bodies, the public has labeled them "nuisance insects." On social media (SNS), videos have been posted one after another showing swarms of lovebugs covering mountain summits and rest facilities.
Complaints have also surged. Lovebug-related complaints filed with Gyeyang-gu reached 504 last year, eight times more than the year before. On one day alone, 159 were reported.
Incheon City and Gyeyang-gu expect the BTI agent experiment to be effective. An Incheon City official said, "We have also secured a budget this year for lovebug control," and added, "We will continue to support the eco-friendly agent trials."
A resident of Gyeyang-dong, a person surnamed Oh, 61, said, "Last year I didn't even dare to hike the mountain," and added, "I hope things improve this year." A resident of Yongjong-dong, a person surnamed Shin, 21, also said, "It was hard because bugs stuck to me while walking," and added, "I expect the control measures to work."