Annual weed control in deciduous trees and vines.
Herbicide treatments used for chemical weed control in deciduous fruit trees and vines in California are enumerated and notes are included on some recently evaluated compounds. Oryzalin at 8-16 lb/acre was safe to use in young trees but caused some injury to newly planted vines; it is highly active against most annuals. In comparison, Rydex [N1,N1-dipropyl-2,6-dinitro-4-trifluoromethyl-m-phenylenediamine] has a broader spectrum of control, possibly a greater safety margin in vines and longer residual activity; excellent control of sown milo [Sorghum bicolor] was obtained with 4 lb/acre for more than 2 years after application. Norflurazon pre-em. controlled a broad spectrum of weeds, but lacked activity against Conyza canadensis, Amaranthus sp. and Melilotus indica. Goal (oxyfluorfen) gave good residual activity against broad-leaved weeds and was safe on trees and most vines at > 8 lb/acre. Goal was the most effective of any of the herbicides tested when injected through the drip irrigation system in a young apple orchard. Such mixtures as simazine + oryzalin or + napropamide and terbacil + Rydex were also tested. The value of irrigation and/or layering for improving herbicidal activity is discussed.