In some areas where a control agent was sprayed before lovebugs (Plecia nearctica) emerged as adults, as many as 98% fewer adults were trapped than in nearby unsprayed areas. However, because the control effect was unclear in some locations, the government plans to continue inspections through July and then decide whether to conduct additional spraying.
◇ At Bukhansan, 98% fewer lovebugs in sprayed areas than in unsprayed areas
According to data submitted by Rep. Kim Wi-sang of the People Power Party to the Ministry of Climate, Energy and Environment (the ministry) on the 27th, traps in an unsprayed location in Bukhansan in Nowon District, Seoul, caught 249 adult lovebugs over two days starting on the 16th. During the same period, traps in a sprayed location in Bukhansan caught only four adults. The number in the sprayed area was 98.4% lower than in the unsprayed area.
Sahmyook University in Nowon District showed similar results. In the unsprayed area, 233 adult lovebugs were caught, while only four were trapped in the sprayed area, a 98.3% decrease. Suraksan in Nowon District also showed a difference: 244 in the unsprayed area versus 22 in the sprayed area, a 91% gap.
In addition, fewer adult lovebugs were found in sprayed areas than in unsprayed areas at ▲ Dodeoksan in Gwangmyeong, Gyeonggi (100%) ▲ Baengnyeonsan in Eunpyeong District, Seoul (84.4%) ▲ Onansan in Siheung, Gyeonggi (71%) ▲ Bongsan in Eunpyeong District (69%) ▲ Gwanaksan Mountain in Anyang (50%).
◇ Control agents sprayed at 18 sites in the greater Seoul area since April
Earlier, the ministry moved preemptively to reduce the number of lovebugs. It sprayed control agents twice starting in April at 18 sites in the greater Seoul area identified as lovebug occurrence zones—five in Seoul, four in Incheon and nine in Gyeonggi. The timing considered that lovebug larvae typically pupate around mid-May and emerge as adults from June.
The operation used a soil bacterium-based control agent, Bacillus thuringiensis israelensis (BTI), developed under the lead of Kim Dong-geon, head of the Environmental Ecology Research Institute at Sahmyook University. BTI acts on the guts of specific insects to kill larvae and is known to have relatively limited effects on plants and surrounding ecosystems.
But the same results did not appear everywhere. In some cases, more lovebugs were caught where the agent was sprayed. On Jeongbalsan in Goyang, Gyeonggi, 67 were caught in the sprayed area, compared with 12 in the unsprayed area. ▲ Cheonmasan in Gyeyang District and Seo District, Incheon ▲ Gahaksan in Gwangmyeong ▲ Seodoksan in Gwangmyeong ▲ Seongjusan in Bucheon also saw more catches in sprayed areas than in unsprayed areas.
Kim, who led the control effort, said, "In some areas, work began in mid-May, the timing of the second round, which is when larvae transition to pupae," adding, "The results may reflect the timing of the spraying."
◇ Results vary by area… "Need to weigh climate effects"
Factors beyond spraying—such as weather conditions and movement paths—may also have affected numbers. With the monsoon delayed and area-specific temperatures and wind patterns shifting, the timing and density of lovebug occurrences may have changed. On the 24th, when the National Institute of Forest Science expected lovebug activity to peak this year, people near Gyeyangsan in Incheon said the numbers were lower than expected. By contrast, northern Gyeonggi areas such as Dongducheon and Uijeongbu saw mass occurrences as early as March to April.
Areas filing complaints about lovebugs have also changed year by year. In 2022, Eunpyeong District accounted for 3,558 complaints—80.5% of all lovebug complaints in Seoul. The following year, they spread to Seoul's northwestern area and Goyang, Gyeonggi, and since then related complaints have continued across the greater Seoul area.
Yang Yeong-cheol, a professor in the Department of Occupational Health, Environment and Safety at Eulji University, said, "Lovebugs have weak flight capabilities and move with wind direction and flow," adding, "It is too early to conclude there is a reduction effect from preemptive spraying."
◇ Kim Wi-sang: "Lovebugs require a nationwide quarantine network"
The government will review the control results through late July and then discuss additional measures through the "insect outbreak response council," involving local governments and experts.
An official at the ministry said, "We will compare changes in flies, other insects and arthropods inhabiting the surrounding soil before and after spraying to decide on additional introductions of the control agent."
Rep. Kim Wi-sang said, "A bill that defines lovebugs as an 'outbreak insect' and imposes a control mandate on local governments passed the National Assembly's plenary session last month," adding, "We urge the operation of a systematic nationwide quarantine network."