Migratory pests from China spread rapidly along southern coast amid climate anomalies

Abnormal weather patterns have allowed migratory pests to take hold across rice-growing areas along South Korea's southern coast.

Migratory pests — including the brown planthopper — ride air currents from China into Korea, and can deal a devastating blow to rice output depending on when they arrive and whether they establish themselves. The South Gyeongsang Province Agricultural Research and Extension Services and local governments along the southern coast have launched a joint surveillance and pest-control operation.

Brown planthoppers and rice leaffolder moths, two of the most damaging summer pests, are threatening rice fields across the southern coastal region, according to Yonhap and the South Gyeongsang Province Agricultural Research and Extension Services on Saturday.

Unlike mosquitoes or aphids, these insects are not native pests that overwinter in Korea. Unable to survive the Korean winter, they die off naturally each year, only to re-emerge every June and July — around the monsoon season — after crossing the sea from areas south of China's Yangtze River on prevailing westerly winds. This migratory behavior is the origin of the Korean term "birae haechung," meaning pests that fly in and cause damage.

Once they arrive, these pests multiply exponentially in the hot, humid summer conditions, posing a serious threat to crops. Early surveillance and control timed to their arrival are therefore essential to stopping them at the source.

Climate change and rising global temperatures have accelerated the movement of these pests in recent years. Hotter, more humid weather has shortened their generational cycle, causing population densities to surge.

This year in particular, brown planthoppers are believed to have entered the country as early as mid-June. They are expected to spread primarily across the southern and western coastal regions.

Among migratory pests, the brown planthopper and the rice leaffolder moth cause the greatest damage to farms. The brown planthopper lives at the base of rice plants and sucks out their sap, causing the plants to yellow and wither. In severe cases, patches of rice paddies collapse as if struck by bombs — a phenomenon known as "concentrated die-off." The rice leaffolder moth is equally destructive: its larvae roll rice leaves lengthwise and feed on them, blocking photosynthesis and sharply reducing both grain quality and yield.

To minimize damage from summer rice diseases and pests, the provincial agricultural research service plans to conduct an 11-week intensive early surveillance program targeting five southern coastal cities and counties — Tongyeong, Sacheon, Goseong, Namhae and Hadong — from this month through Sept. 18. The aim is to block the primary entry routes through which foreign pests first enter the country and prevent damage before it occurs.

Surveillance teams made up of provincial and municipal officials are using suction traps and insect nets to precisely measure pest population densities in rice paddies. The findings are fed in real time into the national pest management system and shared with farmers along with control guidelines.

In addition, the service will conduct three rounds of joint national-regional surveillance with the Rural Development Administration and municipal agricultural technology centers between this month and September. Coordinated pest-control operations using drones and wide-area sprayers are also planned.