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.
Grass weed control to prevent competition with crops for valuable nutrients is likely to prove even more crucial this autumn.
With some growers seeking to make savings on the high cost of fertiliser inputs this season, every unit needs to be focussed on delivering crop yield,
Even a moderate grass weed population could rob over 25% of the nutrients applied to, and intended for, the crop.
Improved fertiliser efficiency is also a key element of driving down the unit carbon footprint for farms.
A robust residual pre-em strategy is now recognised as the cornerstone of an effective autumn grass weed control strategy, especially given that there’s fewer opportunities for good contact control on established weeds later in the season and wider issues of herbicide resistance.
Last season’s Syngenta trials and field-scale work in Staffordshire had demonstrated that Defy-based pre and peri-em combinations performed better than newer grass weed chemistry actives in reducing the populations of weeds. It also proved more cost effective to give better margins.
Newer chemistry is valuable to add another tool for growers in the most difficult grass weed situations and when facing very high populations.
However, the existing options can work very effectively as part of an integrated control strategy in the majority of situations – as has been repeatedly proven over recent seasons,
Results in predominantly ryegrass control situations show that increasing the rate of Defy in a pre-em stack from 2.0 l/ha to 4.0 l/ha would give a higher marginal increase in overall weed control and at significantly lower extra cost, compared to switching to using newer grass weed chemistry.
Growers and agronomists have made significant strides in grass weed control with strategies to reduce both ryegrass and black-grass. That knowledge and experience can continue to deliver gains in sustainable control, against a potential backdrop of tighter arable margins for the coming season.
Pete Hawkins autumn strategy to tackle grass weeds this season includes:
- Manage stale seedbeds for specific target weed species
- Delay drilling for as long as practically possible
- Grow more competitive hybrid varieties
- Use a robust multi-active pre-em stack including DEFY
- Higher rates of DEFY will enhance overall grass weed control
- Apply a peri-em sequence to boost residual activity where conditions allow
- Focus efforts on worst affected fields
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