Mexico pulls out of tomato pricing agreement.(Knight Ridder Newspapers)

MIAMI _ Mexican tomato growers have fired the first salvo in a resumption of trade hostilities, announcing they are pulling out of a five-year-old price agreement that kept the peace with Florida growers.

The decision by Mexico's largest group of tomato growers to withdraw from the agreement _ which sets a price floor on wholesale tomatoes _ will trigger a new probe by the U.S. Commerce Department into whether Mexican tomato producers sell their produce below cost in the United States, a practice known as "dumping."

If Commerce finds no evidence of dumping, Florida growers could face a flood of low-cost tomatoes this winter, a reprise of the situation in the …