20 July 2021, UK: Pre-emergence herbicide timing gives the best chance to target grass weeds, enabling higher rates of application to get long-lasting residual activity, without the danger of crop safety issues.
Susceptible weeds can be effectively controlled as they emerge, whilst seeds drilled below the treatment zone can grow through clear of competition.
However, if weather conditions and workloads prevent pre-emergence application, Defy has the flexibility to still be included in mixes for peri-em and post-em treatments.
Extra care should be taken with application rates and mixes particularly for peri-em applications – from first crop emergence to one-true leaf – to avoid combinations and conditions that could risk crop safety.
Once the crop is larger, through to GS21, issues of potential crop safety from any herbicide mix is reduced. Defy will still control any weeds with soft meristem close to the surface, but generally levels of residual activity would be lower.
A further challenge with peri- or post-emergence treatments would be the variable growth stages at the time of application, which could leave some plants more susceptible to transient damage and slower to recover – especially as growth slows later in the season.
“Trials and growers’ field experience consistently show application as soon as conditions permit after drilling has achieved the most reliable results,” advised Georgina Wood.
“That’s especially true where drilling has beneficially been delayed, to control initial weed flushes, and chances for later herbicide applications could be compromised by weather and soil conditions.”