Citrus growers in California are using predatory wasps to combat a tree bacteria threatening their orchards.

The tiny, parasitic wasps -- scientifically known as Tamarixia radiata -- are imported from Pakistan and are used to attack a species of psyllid that has been spreading a deadly bacteria, known as citrus greening, the Los Angeles Times reported Sunday.

The wasp "is going to be our number one weapon to control to Asian citrus pysllid," said Mark Hoddle, an invasive species expert at UC Riverside, who has been bringing the wasps to California. "We have no other choice except to use this natural enemy or do nothing. And the 'do nothing' option is unacceptable."

Hoddle and his team have so far released more than 75,000 wasps in infected citrus groves.

Meanwhile, U.S. Department of Agriculture has enacted quarantines in nine states, including Florida, Texas and California that prohibit the interstate movement of citrus trees and require special labels on trees from areas where greening has been detected.

In California, nine counties have been quarantined.