Millions of parasitic wasps have been released across 24 US states in an effort to stop the spread of the tree-killing emerald ash borer beetle.
The beetle has killed about 38 million ash trees, according to the US Department of Agriculture (USDA) which has approved the release of four species of wasps, which lay eggs inside the ash borer larvae and prevent them from developing into adult beetles.
The wasp program is unlikely to save any current trees, but rather aims at preventing the ash borer from decimating future tree populations, according to entomologist Ben Slager. “It’s really a long-term management thing,” said Mr Slager, an entomologist at the Michigan laboratory producing the wasps for the federal program.
The wasps have been released in 24 of the 26 states where the insect has been found. The two remaining states, Texas and Georgia, are also expected to introduce the wasp program.
The emerald ash borer, which feeds on a tree’s tissue and prevents nutrients from moving to branches, is believed to have been accidentally introduced in North America during the 1990s through wood-shipping crates from Russia, China, Japan or Korea.
The treatment and removal of the trees affected by the ash borer in the US is estimated to be up to $25bn.