Winter poa annua & barley grass weed control is an essential component of pasture management, especially in new permanent ryegrass pastures in paddocks with a history of winter grass infestations. The quick to establish winter grasses compete with resown grasses for nutrients, water, and light, reducing pasture productivity and quality.
Key points of approach
- Improve pasture and tiller density
- Pre and or post emergent selective herbicide use
- Grazing management for productive pastures
- Multi year summer forage crop programme
Why are they undesirable?
- Hold high levels of moisture – contribute to pugging
- Poor feed quality
- Can crowd out better quality species, reducing productivity
- Short growth cycle – quickly die off in spring – leaving bare patches
- Produce excessive seed – hard to control in following season
By spring the winter grasses (easily spotted with their vivid light green colour) have become reproductive, producing large amounts of seeds, which can remain viable in the soil for several years. The bare patches left by winter grasses can reduce pasture productivity and quality long term.
In late spring pastures when winter grasses perish paddocks are left visibility open and subject to further weed invasion for subsequent years. The target of our approach is to ensure the investment in perennial pastures pays off – by having the paddock in high productivity for the longest period possible.
Thoughts from Adam Fisher, agronomist in Gippsland.
“To combat winter grasses in new ryegrass pastures, a multi-pronged approach to management is recommended” advises Adam Fisher of Notman Pasture Seeds in Poowong
First, proper establishment practices of perennial pasture, such as timely planting (sometimes out of our hands), adequate seedbed preparation (no big clumps), and increased seeding rates (30-40kg/ha), can help reduce the opportunity for winter grasses to establish early.
Densely tillered ryegrasses
“To create a competitive pasture, it is also essential to choose a densely tillered ryegrass. This could include Matrix SE, Stampede CM142 or a Base AR37” Mr Fisher said.
Dense tillering means more shoots per plant, creating a thick plant that can shade out weeds like Poa annua, capeweed, and summer weeds. We also know tiller density also helps pastures withstand pugging and trampling in wet conditions through winter, reducing impact to production and improving the overall health of the pasture.
A high-density sward efficiently utilises nitrogen and gibberellic acid applications in winter by converting more nutrients into productive growth. Rather than the winter grasses taking advantage of the N applications!
Pre-emergent selective herbicides
- Scanner 500 is our top choice
- Disrupts root development of winter grasses
- Provides 60-70 days residual control
- Works best in cultivated soils, with no trash
- Partner with glyphosate for improved knockdown
- Enhances long-term pasture productivity by minimizing seedbank buildup.
Applying pre-emergent herbicide Scanner 500 is a key strategy to prevent winter grass seeds from germinating and establishing in pastures. Using it at 3-4L per hectare before the first autumn rain creates a chemical barrier in the soil, stopping Poa annua and other winter grasses from emerging.
Ethofumesate, the chemical active, disrupts seedling root and shoot development, preventing weed establishment. It is absorbed by emerging seedlings, stopping growth before they reach the surface.
It provides 60-70 days of residual control, provided it is washed through the soil shortly after application. Apply to well-prepared, moist soil with minimal trash for best uptake. Works best in cultivated or lightly disturbed soils.
Can be mixed with glyphosate or paraquat for additional knockdown of existing weeds.
“Selective herbicides, such as Scanner, are effective for controlling annual winter grasses and other grassy weeds, while leaving the desirable ryegrass unharmed”
Grazing management generally ineffective
Grazing or mowing, while useful in managing some types of weeds, is generally ineffective for controlling winter grass. These methods rarely reach the root of the problem, as Poa annua rebounds quickly, continuing its growth and spreading seeds. Without a focused control approach, pastures can rapidly become overrun.
“Heavy grazing, topping or harvesting can reduce the seed production of winter grasses in spring, but in reality there will still be significant amounts of seed set down for subsequent years.”
Summer cropping program before perennial pasture
A multi-year summer forage cropping program is a proactive approach to renovate pastures, control winter grass seed banks before the autumn of sowing perennial pasture. By incorporating forage brassicas, turnips, and pre-emergent herbicides like Trifluralin in the spring beforehand, farmers can strategically break weed cycles, minimise winter grass seed set, and as a bonus, extra summer or early autumn feed.
“We suggest using a strategic renovation programme using forage brassicas or turnips with a pre-emergent Trifluralin herbicides well worked into the soil, followed by a Scanner 500 application in the Autumn.”
Conclusion
In conclusion, a multi-pronged approach is an essential component of good pasture management, especially in avoiding seed set of winter grasses in new permanent ryegrass pastures. Proper establishment, herbicide use, grazing management and mutli year summer crop renovations are all effective strategies for controlling weeds.
Recognising Winter Grasses
Winter grass is easily identified by its light green color, tufted growth habit, and its tendency to seed prolifically. Poa annua matures quickly, typically seeding from late winter through to early summer. This rapid life cycle and extensive seed production allow it to spread aggressively, making it challenging to control once it has established itself in pastures.
Scanner 500 SC
Scanner 500 SC, for selective weed control of winter grasses and weeds in ryegrass pastures and seed crops and established turf.
Active Constituent: 500 g/L Ethofumesate
