Load up for long life with autumn pre-em residuals
22 August 2022, UK: Syngenta Technical Manager and grass weed specialist, Pete Hawkins, looks ahead to the season’s challenges and results from trials to find cost-effective solutions for growers.
Cool and dull weather conditions around the grass weed seed-setting timing in early June indicate a higher than normal level of seed dormancy this season that will increase challenges for control.
It puts extra focus on the importance of stale seedbed preparations, as well as delaying drilling and the need for more persistent pre-emergence herbicide applications – to cover the risk of extended grass weed emergence more effectively.
Stacking additional active ingredients at the pre-emergence timing has been shown to consistently increase the control of both ryegrass and black-grass. Trials have repeatedly shown using a higher rate of Defy always gives an incremental gain in control of both grass weeds.
Pete Hawkins pre-em priorities
- Maximise stale seedbed opportunities
- Delay drilling if possible
- Sow competitive varieties
- Increase the number of actives in mixes
- Maintain good rates of DEFY in the mix
- Extend residual control with DEFY peri-em (if not used pre-em)
Risk management
With the benefits of later drilling and pre-emergence herbicide timing, however, comes the increasing risk that rain and soil conditions could prevent follow up applications. That makes it essential to load extra active ingredients into the pre-em application for the best control possible.
Where drilling has been delayed, herbicide residual activity will also remain more effective in cooler weather conditions and shorter sunlight hours with later season applications.
A series of trials in 2020-21 showed adding Defy at 3.0 l/ha into pre-emergence mixtures gave up to 23% increase in black-grass control, including in combination with newer chemistry actives.
Results from new high-pressure black-grass trials in Yorkshire last season confirmed that Defy boosted levels of control in every treatment in which it was applied.
Proven results
New chemistry does offer a useful option for grass weed control in some particularly challenging situations. But, mindful of the pressures on gross margins with high costs for crops going into the ground this autumn, DEFY provides an extremely well proven and cost-effective opportunity to maintain high levels of control.
Defy should be at the core of pre-emergence herbicide stacks in all ryegrass situations, along with other grass weed treatments in winter barley crops, where newer chemistry options are limited.
If newer chemistry has been used at initial timings, Defy still gives the opportunity to boost residual control from peri-em applications.
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