How China is breeding a beetle army to defend the Three Gorges Dam from plant invasion
- Scientists learn from successful use of the insect in the US to tackle plant pest that arrived with Japanese occupation
- Today, voracious eaters are raised in greenhouses over winter and released in spring
Scientists are breeding millions of beetles for a battle against a weed that threatens to choke rivers across China and bring one of the country’s great engineering achievements, the Three Gorges Dam, to a halt.
Alligator weed is native to South America but was introduced to the Yangtze River in 1937 by the occupying Japanese as a feed crop for their horses. It was not until the 1980s that researchers realised what people living along the river knew – the prolific alligator weed was a menace.
After the second world war, it was grown across southern China for animal feed, garden greening and herbal medicine. That growth came at a price. Other crops such as rice could not compete with the weed for nutrition, sunlight and space, and it began to choke the life out of fish and other aquatic species.
Farmers attacked the plant with sickles and bulldozers, while others tried herbicides. Physical and chemical measures were costly, damaging to the environment, and they could not kill the alligator weed.
Engineers said alligator weed could block filters at infrastructure like the Three Gorges Dam, reducing the amount of water to turn the turbines that create electricity and disrupting river traffic.