Jointed Goatgrass – A Growing Problem in PNW Winter Cereals

Chapter 5 – Weed Control, No. 3, December-January 1985

Roger Veseth

Jointed goatgrass (Aegilops cylirzdrica) is a winter annual grass that was introduced from Europe earlier this century. It has been spreading rapidly and is now a widely distributed problem weed in winter cereal areas of the Pacific Northwest. In addition to the yield losses from this competitive weed, grain contaminated with jointed goatgrass cannot be certified and is subject to dockage at the elevator.

The similarities in life cycle, appearance and seed size between jointed goatgrass and winter cereals make it very difficult to control. Jointed goatgrass seeds may also have a long dormancy with germination rates often less than 50 percent for 6 months to a year after maturity. No presently available herbicides are effective in selectively removing jointed goatgrass from winter wheat or winter barley. Rotations and cultural practices are the main control methods.

STEEP researcher Don Rydrich, Oregon State University agronomist at the Columbia Basin Agricultural Research Center near Pendleton, has been evaluating winter wheat yield losses from jointed goatgrass competition. Table 1 shows that jointed goatgrass is a serious competitor with winter wheat, even at low populations. Jointed goatgrass populations of 5 plants per square foot reduced wheat yield by 24.6 percent. In 1982, 8 plants per square foot reduced yield 29.4 percent.

Table 1. Jointed goatgrass competition in Stephens winter wheat, Columbia Basin Agricultural Research Center, Pendleton, OR (Rydrych, Oregon State University, Agricultural Experiment Station Special Report 680, 1883).

Rydrich points out that jointed goatgrass is a low-profile competitor, staying relatively unnoticed until heading. Its vigorous root system competes well with winter wheat for moisture and nutrients, however. The weed populations in Table 1 consumed 0.4 inch extra soil water in 1981 and 0.9 inch in 1982. This was in addition to the total soil water used by the wheat crop.

Dean Swan, Washington State University Extension weed specialist, recently completed Pacific Northwest Extension Publication 256, Jointed Goatgrass. It includes numerous colored pictures and is a helpful guide for identifying the nature and characteristics of the weed. Swan also reviews the extent and severity of the weed infestation and discusses available control measures. Following are some highlights in prevention and control considerations:

1. Preventing infestations through planting clean seed and equipment sanitation is of prime importance.
2. If the weed is present along field margins, mowing to prevent seed set and planting competitive perennial grasses are possible considerations.
3. When harvesting infested fields, reducing the air on the combine and cutting low will help remove more of the seed from the field. Straw and chaff catchers will also help.
4. Growing spring crops to allow germination of a majority of the jointed goatgrass seeds is the most effective control. At least two successive years of spring crops out of three crop years is suggested. Spring barley appears to be a good competitor.
5. Delay fall seeding to allow elimination of jointed goatgrass seedlings with contact herbicides or tillage.

A copy of this publication is available through the Agricultural Extension Agent in your county.