TALLAHASSEE, Fla. (AP) _ Florida's billion-dollar citrus industry suffered probably its worst blow in the 2-year-old struggle against citrus canker when scientists confirmed the disease has attacked a mature, fruit-producing grove in Manatee County.

State agriculture officials confirmed the discovery Thursday at the Manatee Fruit Co.'s fresh-fruit grove near the town of Palmetto, marking the first time canker has been found in a mature commercial grove during the recent rash of canker discoveries.

Dr. Sal Alfieri Jr., director of the Department of Agriculture's Division of Plant Industry, said about 150 acres of the 360-acre grove have been infected.

Agriculture officials quarantined the grove immediately.

Officials believe the strain of canker that attacked the grove might be a more potent variety discovered only recently in Florida, said Phyllis Habeck, a spokeswoman for the division. But laboratory analysis was pending.

The new strain of canker, found in other citrus-producing countries, is more aggressive and thought to spread more easily than the milder Florida strain which has infected only young trees in 18 nurseries and two immature groves since 1984.

The Asiatic strain was found last month in residential yards on Anna Maria Island near Manatee County and in Holmes Beach near St. Petersburg.

Asiatic strain caused the first Florida outbreak of canker in 1912. That eradication battle took two decades. In the latest fight, more than 10 million seedlings, saplings and young trees have been uprooted and burned, the only known method of destroying canker.

Alfieri said about 900 trees of a total of 20,000 were affected in the grove. He said 50 acres were moderately to heavily infested, while 100 acres had scattered infestation.

U.S. Agriculture Secretary Richard E. Lyng on Thursday announced that Florida would receive $250,000 in federal funds to help with the canker program. His announcement came before canker was confirmed in the Manatee grove.