The fight against a disease threatening California citrus got a boost Tuesday when the U.S. Department of Agriculture said it would expand efforts to breed and release a tiny parasitic wasp, a natural enemy of a pest that spreads the incurable ailment.

In recent months, federal agriculture officials have coordinated a multi-agency effort to contain the spread of huanglongbing, also known as citrus greening, a disease that has infected and killed thousands of citrus trees in Florida and is now threatening California's $2-billion citrus industry.