People who lived next to fields where fungicide maneb or herbicide paraquat had been sprayed were, on average, about 75 percent more likely to develop Parkinson's, California study shows. And: Maneb often goes on potatoes, tomatoes, lettuce and corn; paraquat is used on corn, soybeans, fruit (click 'See also'). Map of their use mirrors areas of U.S. where people are more likely to die of Parkinson's disease.