Jointed goatgrass, Aegilops cylindrica
Also known as cylindrical goatgrass.
Weed identification:
- Seedlings have narrow, grass-like leaves with fine hairs on the leaf margins.
- Mature plants are erect, cool-season annual grasses growing 1-3 feet tall.
- Stems are hollow and jointed, similar to wheat but often with more hair on each node. Nodes are often harder than wheat.
- Inflorescences are a distinct cylindrical spike with multiple segments (joints), each containing one to three seeds.
- Seeds are encased within joints of the spike, resembling wheat seeds but enclosed in a rigid, jointed structure. Each seed can produce one or two seedlings.
Jointed goatgrass seedling
Image credit: Steve Dewey, Utah State University, Bugwood.org
Jointed goatgrass stem
Image credit: Joseph M. DiTomaso, University of California, Davis, Bugwood.org
Biology and life cycle:
Growth habit: Jointed goatgrass is a winter annual weed species that has a similar growth habit and competitive ability to wheat. Germination takes place in the fall; seedlings overwinter and resume rapid growth in the spring. Plants reach reproductive stages in late summer. Requires cool temperatures for germination, typically emerging in late summer to fall. Dormancy can last 1-3 years, with seeds often persisting in the soil seed bank.
Pollination: Primarily self-pollinated but capable of limited cross-pollination. Hybridization with wheat is possible, leading to genetic contamination
Seed production and viability: Produces 50-100 seeds per plant, enclosed within spikelets. Seeds remain attached to the spike, contributing to dispersal through contaminated equipment and grain. Seeds can remain viable in the soil for 2-5 years under favorable conditions; buried seeds persist longer than those on the soil surface.
Genetics: Jointed Goatgrass has a chromosome designation of CCDD, meaning it inherits two sets of chromosomes from each of its two ancestors. Each set consists of seven chromosomes, totaling 28. In contrast, wheat has three ancestral genomes, resulting in six sets of seven chromosomes.
Resistance
Jointed goatgrass has limited confirmed herbicide resistance cases. Resistance to Group 2 (ALS inhibitors) has been reported, but remains rare in this species. There is no widespread documented resistance in Colorado at this time.
Jointed goatgrass inflorescense features (right), compared to wheat inflorescences (left)
Image credit: USDA APHIS PPQ, Oxford, North Carolina, Bugwood.org
Jointed goatgrass infestation in wheat. A native to Asia, is a serious problem in wheat producing areas of the United States. It hybridizes with wheat and outcompetes the crop for nutrients and water.
Image credit: Phil Westra, Colorado State University, Bugwood.org
Jointed goatgrass field infestation
Image credit: Steve Dewey, Utah State University, Bugwood.org
Integrated weed management strategies based on Colorado cropping systems:
Prevention
- Use certified, weed-free wheat seed to prevent contamination
- Clean equipment thoroughly between fields to reduce seed spread
- Rotate fields with non-host crops like broadleaf species to disrupt lifecycle
Cultural control
- Plant competitive wheat varieties to suppress weed establishment in early fall
- Adjust planting dates to favor wheat over Jointed Goatgrass emergence
- Utilize cover crops to reduce seedling establishment
Mechanical control
- Deep tillage can help bury seeds beyond emergence depth, but minimal tillage reduces seedbank longevity
- Mowing before seed set can reduce seed production
- Harvest weed seed control (e.g., chaff carts) can help reduce seed return to the soil
Chemical control
- Selective herbicides such as imazamox (Clearfield wheat system) can control jointed goatgrass in wheat
- Pre-emergence and post-emergence applications of Group 2 herbicides (ALS inhibitors) can be effective but require rotation to prevent resistance
- Tank-mix herbicides with multiple modes of action to reduce selection pressure
References
References
References:
Rodriguez, J. A. (2018). An ALA122THR substitution confers imazamox-resistance in jointed goatgrass (Aegilops cylindrica host.) (Doctoral dissertation, Washington State University).
Donald, W. W., & Ogg Jr, A. G. (1991). Biology and control of jointed goatgrass (Aegilops cylindrica), a review. Weed Technology, 5(1), 3-17.
Gandhi, H. T., Mallory-Smith, C. A., Watson, C. J., Vales, M. I., Zemetra, R. S., & Riera-Lizarazu, O. (2006). Hybridization between wheat and jointed goatgrass (Aegilops cylindrica) under field conditions. Weed Science, 54(6), 1073-1079.
Fleming, G. F., Young, F. L., & Ogg Jr, A. G. (1988). Competitive relationships among winter wheat (Triticum aestivum), jointed goatgrass (Aegilops cylindrica), and downy brome (Bromus tectorum). Weed Science, 36(4), 479-486.