SARE 2001 Highlights

Broccoli Rotation Reduces Wilt in Strawberries Without Fumigation

Above: A California researcher who tested growing broccoli before strawberries to control wilt—commonly managed with methyl bromide—found he could consistently reduce the disease by diversifying the rotation and incorporating crop residue. A worker at the Monterey Bay Academy managed by the California Strawberry Commission shreds broccoli residue. Photo by Krishna Subbarao.

Strawberry growers have long relied on the soil fumigant methyl bromide to control soil-borne diseases such as Verticillium wilt that can devastate the valuable crop. As supplies of the chemical—to be pulled off the market by the U. S. EPA in 2005—dwindle and become more expensive, researchers are seeking new environmentally sound, cost-effective ways to control strawberry wilt. Armed with a SARE grant, University of California-Davis researcher Krishna Subbarao has tested a promising rotation using broccoli, a crop he found in earlier research to suppress the disease. In that research, where Subbarao introduced broccoli into cauliflower rotations, he found that growing broccoli and incorporating its residue into the soil suppressed 95 percent of the microsclerotia—structures that cause the disease—and reduced wilt in subsequent cauliflower crops. In his SARE project, Subbarao tested broccoli in rotations with strawberries to see if he would get similar results. He also experimented with lettuce and Brussels sprouts, commonly grown in northern California, in the rotation. Thus far, broccoli rotations look the most promising to control wilt. Researchers found rotations of broccoli-broccoli-strawberries—with broccoli residue incorporated prior to strawberries—exhibited the same suppression abilities as in their earlier work. While growing two crops of broccoli prior to strawberries is less profitable than growing strawberries year round, growers can realize some economic return. Moreover, with methyl bromide costing up to $2,000 an acre, a non-chemical alternative is an attractive solution. Area growers are interested. An organic strawberry grower has adopted the rotation, while three large conventional strawberry growers are testing it. "If growing broccoli reduces Verticillium wilt in the post-methyl bromide era, while giving a reasonably high strawberry yield, it will be a significant boon for the growers," Subbarao says.

[For more information, go to http://www.sare.org/projects/ and search for SW99-009]

Top