Chemical Control of Weeds in Potatoes in Southcentral and Interior Alaska

Abstract

Weeds cause serious problems for commercial potato growers in Southcentral and Interior Alaska. Reductions in potato yields of 20 to 70 percent due to weeds have been observed in previous studies (Carling, unpublished data). Competition by weeds generally is so intense that profitable yields cannot be produced unless weed growth is controlled. Mechanical methods alone, including cultivation and hilling, have not provided acceptable levels of control. For many years, commercial potato growers relied on the chemical herbicide Premerge® (dinoseb) to control weeds. Premerge killed weeds by contact and was very effective in controlling the most troublesome broad leaf weeds when applied just prior to emergence of the potato plants. In addition, Premerge left no chemical residues in the soil to damage vegetable or other crops grown in succeeding years. Unfortunately, several years ago Premerge was found to be a hazard to human health and now may not be used as an herbicide. Commercial growers have been trying other chemicals as they search for alternatives to Premerge. Several of these chemicals are promising but, unlike Premerge, all leave chemical residues in the soil that could be toxic to crops that potato growers plant in rotation. In 1988, a field study was initiated to evaluate the efficacy and carryover of several herbicides. Five chemicals including: Treflan® (trifluralin), Enide® (diphenamide), Eptam® (ETPC), Sencor® (metribuzin) and Lorox® (linuron) were evaluated at Fairbanks and Palmer. Eptam, Sencor and Lorox controlled weeds most effectively of the five and were selected for reevaluation in 1989. Summarized in this report are data on potato yields and weed control from the study in 1989. Information on phytotoxic residues associated with some of these chemicals will be presented in later publications.