Key features of grass weeds
- Grass weeds are monocots meaning that each seed initially contains one embryonic leaf (cotyledon)
- Long and often narrow blades (leaves) with parallel veins
- Stems usually hollow
- Usually small inconspicuous spikelets (spikelets are the flowering unit of a grass)
- Grass weeds are summer annuals, winter annuals or perennials
As many important cereal crops (oats, barley, wheat) are also grasses, it can make identification of grass weed problems challenging in the field. 'How to identify grass weeds in arable fields' on the AHDB website is a useful tool for in depth identification.
There are a number of management options with the main ones being cultural and chemical (herbicide) control.
- A wide range of cultural control techniques can be employed specific to the targeted grass weed. This may include using optimal rotations, tillage and cultivations, suitable crop row spacing, using competitive crop varieties/cultivars and altering key timings (e.g drilling dates).
- The aim is to have optimal field conditions that make it more challenging for weed population establishment and growth.
- For example delayed drilling of winter wheat is a commonly recommended to avoid the main black-grass flush.
- A wide range of pre-emergence and post-emergence herbicides can be used on grass weeds - most commonly this includes ALS inhibitors (e.g sulfonylureas) (HRAC Group 2) and ACCase inhibitors (HRAC Group 1)
- Some other pre-emergent options: HRAC Group 3 inhibition of microtubule assembly (Pendimethalin, trifluralin), HRAC Group 15 Inhibition of long-chain fatty acid synthesis (Flufenacet, tri-allate),
- Some other common post-emergent options: HRAC Group 9 inhibition of EPSP synthase (glyphosate)
- Widespread target site resistance and enhanced metabolism resistance to ALS and ACCase inhibiting herbicides has been reported across many grass weed species. Often seeing multiple resistance in populations and resistance is a growing problem.
- This has increased the reliance on pre-emergent options and glyphosate - putting increasing pressure on weeds to become resistant to glyphosate. As such a widely relied upon herbicide, glyphosate resistance risk should be continually monitored.
- Genetic testing has elucidated some of the common mutations responsible for TSR in grasses.
- Regular monitoring and resistance testing is recommended along with integrating cultural control methods.
Please attach any relevant projects or pages linked to grass weeds to to this topic page.