Johnsongrass, Sorghum halepense, is the most serious perennial weed control problem in California orchards. This fast-growing, warm-season weed propagates prolifically from seed and underground rhizomes. The fleshy underground stems provide the necessary overwintering mechanism by which this plant gets an early start in competing with crop plants, as well as other weeds. In established trees and in young, producing orchards, competition from Johnsongrass may reduce nutrients, moisture, and light. In a field test at the Kearney Field Station, Fresno County, Johnsongrass seedlings were controlled in the nursery row with various soil-persistent herbicides. MSMA is not currently registered (or recommended by University of California) for orchard use. Dalapon is not registered for use on walnuts or almonds.

Photos by Tracy Borland. Cooperators and contributors to this study included B. Fischer, L. Brown, T. Aldrich, H. Kempen, L. Hendricks, C. Hemstreet, N. Ross, L. Smith, J. Yeager, D. Bayer, and W. B. McHenry