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Overview
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Registration
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Plan Your Blackgrass/Grassweed Management
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A crucial step to achieving successful control of headache grassweeds in winter wheat – blackgrass, ryegrasses and sterile brome, is to monitor when grassweeds emerge, so that post-emergence treatments can be applied as soon as possible when the weeds are small and are actively growing.
To help growers and advisers understand growth of these weeds, Dow AgroSciences is funding an ADAS monitoring scheme once again this season.
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If you would like to receive the latest GEM report directly to your inbox or would like to find out more about this service, please contact our Technical Hotline on 0800 689 8899, your local Dow AgroSciences representative or E-mail.
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GEM first began in the autumn of 2010, and already some key factors influencing emergence patterns have been recognised - the rapid emergence of sterile brome being one of them. Sterile brome is most effectively controlled in the autumn when small.
This year we are hoping to monitor five representative UK sites in Cambridgeshire, Herefordshire, Oxfordshire, Wiltshire and North Yorkshire. As in previous years this will involve monitoring:
Three sown major grassweeds: Blackgrass, sterile brome and Italian ryegrass (all sown 500 seeds/m2) and a 'natural' unsown blackgrass population. Two planned drilling dates - late September and late October - but this hasn't gone to plan!
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Report 6 - 14th December 2012
Another cold week cold week across all sites with average minimum temperatures below 0°C and average maximum temperatures at just 6°C. Emergence at some sites last week could not be assessed due to snowfall. Soil temperatures are now below 6°C across all sites with the lowest temperatures recorded in Cambridge at 4.4°C. Finally we are experiencing a little less rainfall and Oxfordshire and Wiltshire have experienced their ‘driest’ week since 23rd October with around 5 mm. Since our last report, there has been little change in grassweed population numbers or size as a result of the cooler temperatures and wet soils. Emergence has commenced in all sown weeds at the late-drilled Cambridgeshire site which was drilled on the 20th November. Similar emergence is being seen in the early drilled Cambridgeshire site with low levels of blackgrass, sterile brome and Italian ryegrass germinating. The first sign of emergence in the unsown blackgrass population has also been seen at the early drilled Cambridgeshire site at low levels. Second sowings in Oxfordshire and Yorkshire both drilled on 20th November have yet to see any emergence whilst Wiltshire is still not drilled. Interestingly in Herefordshire more weeds have emerged at the late drilled site than the early drilled site. These populations fell at the end of November, most notably Italian ryegrass, which was attributed to waterlogging. Growth stages of grassweeds in both the early drilled and late drilled crops have remained unchanged with all grassweeds between 1-3 leaf, with the exception being in Herefordshire on the early sown sites where sterile brome is now at 3-6 leaves.
All sown grassweeds are drilled at 500/m2
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Current advice for grassweed control in winter wheat:
Although growth has still been evident at some sites, the recent drop in soil and air temperatures means that conditions for application of pyroxsulam may now be sub-optimal. With many grassweeds going into winter small, there is still time to achieve effective grassweed control from later applications. Growers should be vigilant if conditions turn mild and favour active growth as these are good opportunities for grassweed control with UNITE or Broadway Star.
For crops that are yet to receive a residual herbicide, a priority would be to apply as soon as you can travel. This will help to hold back size of grassweeds for follow up treatments when active growth resumes.
If growers can travel apply a residual herbicide appropriate to the target weed:
- 240 g ai/ha flufenacet up to the end of December (Blackgrass)
- 120 g ai/ha flufenacet + additional residual e.g. PDM or prosulfocarb from 1st January (Blackgrass)
- Min 1,000 g ai/ha PDM (Blackgrass/brome)
- Min 1,500 g ai/ha CTU combinations (Ryegrass*)
*Please note there is no specific requirement for use of a residual programme partner with Broadway Star + adjuvant for control of ryegrass but it will help give greater flexibility for later timings. However it is important where there is ACCase resistance as in this case fop / dim chemistry would not be effective program partners. The use of residual partner may also offer similar benefits in control of wild oats.
Follow-up treatments should then be made once active growth resumes and approximately 4 weeks after the residual spray. Additional residual may be needed.
Use UNITE where blackgrass is the driver-weed.
Use Broadway Star where ryegrass, wild oats and bromes are the driver-weeds.
Learn more about UNITE
Learn more about Broadway Star
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It is important to remember that germination of grassweeds will also be subject to local factors and the information provided by GEM should supplement but not replace field monitoring.
