SHIJIAZHUANG - Forestry authorities in North China's city of Baoding released 600 million bees this month to kill off American white moths, which have plagued large areas of crops and forests.

White moth infestations have been detected on 20,000 hectares of farmland and forests in the city so far this year, said Duo Jianguo, head of the Baoding forest epidemic prevention station on Monday.

He said that this year marks the fifth year in a row that authorities have used bees to kill the moths, as they are an effective and environmentally friendly form of pest control.

The bees use their stingers to bore into white moths' pupa and kill their larvae. The bees have been previously used to eliminate moth infestations in the provinces of Hebei and Shandong.

Known as the "forest locust," the moths can destroy more than 300 plants and consume the leaves of two hectares' worth of poplar trees within two days.

According to the State Forestry Administration, the pest has threatened plants and crops in Beijing, Tianjin, Shaanxi, Hebei and Shandong since it was first detected in Liaoning province in 1979.