Integrated Management of Jointed Goatgrass in the Pacific Northwest

Integrated Management of Jointed Goatgrass in the Pacific Northwest

EB2042E
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Joseph Yenish, Associate Professor, Washington State University, Daniel Ball, Professor of Weed Science, Oregon State University, Roland Schirman, Extension Coordinator (PNW), National Jointed Goatgrass Research Program, Washington State University
Jointed goatgrass is a major problem in most winter wheat-growing areas west of the Mississippi River. This publication discusses best management practices for the prevention and control of jointed goatgrass infestations, especially in the specific climate and cropping systems of the Pacific Northwest.
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Overview

Jointed goatgrass (Aegilops cylindrica) is an annual invasive grass weed that is particularly troublesome in winter wheat fields in the western United States. The severity of the infestation has increased over the past 50 years in many areas to levels that reduce yield and quality significantly. Native to southeast Europe, jointed goatgrass is believed to have been introduced into the United States in contaminated wheat in the late 1800s. Spikelets of jointed goatgrass cannot be completely removed from contaminated wheat grain with conventional sieves or with special length-grading seed cleaners. This has prompted the grain industry to increase the penalty when goatgrass spikelets are part of the dockage, which further lowers the market price of contaminated wheat.

Although jointed goatgrass is a major problem in most winter wheat growing areas west of the Mississippi River, the climate and cropping patterns of the Pacific Northwest (PNW) are unique and may influence the choice of options available for effective management of this pest. In particular, producers have noted that by adopting direct seed/reduced tillage management systems, both the number of jointed goatgrass infestations and the densities of these infestations tend to increase.

Jointed Goatgrass Biology

Jointed goatgrass is a winter annual grass weed that closely mimics the life cycle of winter wheat, and has a similar life cycle to other grass weeds of importance such as downy brome

Figure 1. Collar region and seed of jointed goatgrass (far left), wild oat (center), and downy brome (right). Note hairs along edge of leaf; the small ligule (membrane located behind the stem where the leaf blade meets the leaf sheath); and short, stiff hairs at the collar region and along leaf margins of jointed goatgrass.
and, to a certain extent, wild oat. Jointed goatgrass can be distinguished from these other grass weeds by the presence of short, stiff hairs on its leaf margins (Figure 1). As with most winter annual grasses, seed germinate in the fall with emerged plants overwintering and resuming growth in the spring. Although jointed goatgrass seed typically germinate in the fall, it can also germinate during March and April and still produce viable seed. Spring-germinated plants usually mature and produce seed later than fall-germinated plants. As jointed goatgrass plants mature, intact spikelets (joints) (Figure 2) shatter and fall to the soil surface beginning about three weeks prior to wheat harvest and continue to do so up to wheat harvest. Scientists in Washington recently discovered that jointed goatgrass can produce seed without vernalization (an overwintering chilling period). It seems clear that merely rotating to a spring cereal may not completely eliminate jointed goatgrass seed production in that crop, without additional production changes.

Seed can remain viable in the soil for up to five years (Figure 3), especially in drier regions and when deeply buried. Seed will typically decay faster in a region with higher precipitation. A study in the PNW showed that seed remained viable for more than five years in a 10-inch rainfall area, compared to less than three years in a 22-inch rainfall area. In addition, most jointed goatgrass seed will germinate and emerge from soil depths as great as two inches. Approximately 80% of the seed placed between the surface and a depth of two inches will germinate within three years. Some seed will emerge from depths of two to three inches, but very few will emerge from soil depths greater than four inches. The optimum temperature

Figure 2. On the right side is a single intact jointed goatgrass spikelet (joint) with two seeds that have been removed from a spikelet. On the left is a single spikelet with two seedlings emerging from seed which are inside.

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Copyright 2016 Washington State University

Published May, 2009

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