Annual weed competition in young orchards and vineyards can often reduce first-year growth as much as 50 percent. In fields with extremely heavy weed populations and limited irrigation, trees and vines have been killed by weeds in the first year. Perennial weeds are even more harmful than annual weeds to newly planted trees and vines. Even though a persistent tillage program can give a practical control of perennial grasses, many growers still have serious problems with perennial weeds.

The authors wish to acknowledge the excellent cooperation of Norman Ross, Farm Advisor, Stanislaus County; H. Agamalian, Farm Advisor, Monterey County; D. Holmberg, Yolo County; J. DeTar, Solano County; L. Hendricks, Merced County; V. Schweers, S. Sibbett, J. LaRue, W. Peacock, Tulure County; L. Brown, Kings County; J. Foott, San Luis Obispo County; Warren Bendixen, Santa Barbara County; Ron Tyler, Santa Cruz County; W. Humphrey, Orange County; E. Roncoroni, Staff Research Associate, U.C. Davis; J. Schlesselman, Les Nygren, and R. Goertzen, Staff Research Associates, Kearney Field Station; the Stauffer Chemical Company and Eli Lilly and Company for their financial and technical support.