Herbicides, or weed killers, are the most commonly used pesticidesin California, but the pesticide that causes the most worker injuries is sulphur, used as an insecticide and a fungicide, says Patrick Marer, pesticide coordinator for the Integrated Pest Management program at UC Davis and a key speaker at an upcoming symposium on preventing and treating pesticide illnesses. "It causes about half of all the reported worker injuries per year," Marer estimates. Ironically, sulphur is commonly used by organic growers, he says. The symposium, sponsored Sept. 27-28 by the UC Davis School of Medicine in the Veterans Affairs Medical Center in Fresno, will bring together some 15 speakers, all experts in their fields. Some speakers are "cluster busters," health experts who probe clusters of cancers, genetic abnormalities and other chronic conditions that may be linked to pesticides. Marer will discuss "Pesticide Use and Major Crops: Statewide Focus" at 9:30 a.m., Friday, Sept. 27.