The effects of several preemergence herbicides at various rates were tested on bearing Redblush' grapefruit trees and non-bearing Navel orange trees. Some of the preemergence herbicides caused foliar injury symptoms on the trees including Hyvar X Diuron, and Krovar I although they did not cause significant yield reductions in the short time period of this experiment. Several herbicides including Solicam, Surflan, and Prowl did not cause foliar injury or reduce yield and provided good weed control for various lengths of time. The Prowl treatments provided the longest period of weed control in the experiment on bearing grapefruit trees.

When applied early-postemergence, Milestone at 0.75 and 1.0 lbs-ai/A provided excellent control of summer annual grasses and broadleaf weed for as long as 4 months, equivalent to Karmex. Princep and Krovar also provided good weed control but appeared to offer slightly shorter residual against some broadleaf species. Solicam, although it provided good weed control, particularly of the grasses, was the weakest material evaluated in this trial. Although Karmex is notorious for causing crop injury on the sandy soils of the Yuma Mesa, we did not detect any injury from this herbicide or any others in this trial.