In a San Joaquin Valley peach and nectarine research plot treated with compost made from city dwellers' lawn clippings, tree prunings and leaves, the incidence of the dreaded stone fruit disease brown rot has been surprisingly low two years in a row. Its presence was significant, however, in adjacent research plots treated with traditional composts and fertilizers at typical levels. San Joaquin Valley-based UC Davis plant pathologist Themis Michailides doesn't know why "green waste" appears to reduce brown rot, but he has a theory. "We found in plots treated with urban compost that there were millions of yeast spores on the fruit surface," Michailides says. "The more yeast we had on the fruit, the less brown rot developed." The green waste compost may carry the harmless yeast into the orchard or provide a more favorable environment for the yeast to grow in and thrive, he says. Its presence also may block development of brown rot. Research continues this year on the project, which could lead to the reduction of waste reaching urban landfills by thousands of tons per year.