Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: February 7, 2008
Publication Date: July 16, 2008
Citation: Boydston, R.A. 2008. Yellow Nutsedge Biology and Control in Potato Rotations. Proceedings 47th Washington State Potato Conference, pp 9-12. Technical Abstract: Yellow nutsedge (Cyperus esculentus L.) is a native perennial weed common in irrigated row crop production throughout most of the U.S. Yellow nutsedge is particularly problematic in crops that do not provide adequate shading, such as onions. The weed competes strongly for water, nutrients, and light and management practices including frequent irrigation and high nitrogen fertilization stimulate yellow nutsedge growth . Yellow nutsedge tubers are able to grow into potato tubers causing them to be graded as culls. Yellow nutsedge biology and identification are discussed in detail. Integrated control methods for yellow nutsedge including growing competitive crops, cultivation, biological controls, fumigation, and use of herbicides are discussed. Potatoes compete fairly well with yellow nutsedge, especially when planted early and when conditions favor potato growth and early canopy closure. Planting certified potato seed and avoiding planter skips will help provide a competitive potato canopy. Soil fumigation with metham sodium can reduce yellow nutsedge tuber viability but control is variable. Fumigant efficacy depends on the dose reaching the nutsedge tubers and the physiological stage of the tubers when fumigated. Glyphosate applied at 1 to 3 lbs ai/a controls top growth of yellow nutsedge, but new sprouts usually emerge later. Herbicides that suppress or control yellow nutsedge in potatoes include EPTC applied PPI, metolachlor or s-metolachlor and dimethenamid-p applied PRE, and rimsulfuron or metribuzin applied PRE or POST. A new nonregistered herbicide was tested in potatoes in 2007 in Washington and Oregon. Both preemergence and sequential applications (preemergence followed by postemergence) of this herbicide suppressed yellow nutsedge well without injury to potatoes at both locations. Sequential applications controlled the weed more consistently at both locations. Treatments of s-metolachlor and dimethenamid-p applied preemergence in container trials reduced the number of viable tubers to less than 6 per container compared to 34 to 88 tubers produced by nontreated control plants. Growth of yellow nutsedge shoots was reduced by 90% or more by both herbicides over the 6 week period. S-metolachlor and dimethenamid-p applied to emerged yellow nutsedge in the 2-leaf stage was less effective than preemergence applications, but still reduced the number of viable tubers produced by 72 to 93% compared to nontreated plants.