Don't court returns with low herbicide rates

Increasing pre-emergence Defy application rate to 4.0 l/ha could reduce Black-grass seed returns by the same weight of grass seed per m2 as used to sow Wimbledon Centre Court.

Results of trials at Syngenta Black-grass Innovation Centres have consistently shown the increased control from a higher rate of Defy in the autumn pre-emergence herbicide stack, reported the company’s cereal herbicide campaign manager, Melanie Wardle.

Increasing the rate of Defy in a pre-emergence stack from 2.0 l/ha to 3.0 l/ha, reduced Black-grass seed return by an average 160 kg/ha - equivalent to the seed rate typically used to sow a lawn, and all the crop competition that density of cover would entail, according to Mel Wardle of Syngenta

placeholder image — Increasing the rate of Defy in a pre-emergence stack from 2.0 l/ha to 3.0 l/ha, reduced Black-grass seed return by an average 160 kg/ha - equivalent to the seed rate typically used to sow a lawn, and all the crop competition that density of cover would entail, according to Mel Wardle of Syngenta

“Increasing Defy rates from 2.0 l/ha to 3.0 l/ha reduced Black-grass seed return by an average 3200 seeds per m2 – an equivalent to 160 kg/ha,” she highlighted.

Further increasing the rate, to 4.0 l/ha, gave another step change in improved control – reducing seed returns by more than 5800 Black-grass seeds per m2, or 290 kg/ ha, compared to the 2.0 l/ha rate.

“Reduced rates of control not only hits yields of the growing crop, but the enormous seed return has long-term implications right through the rotation and the potential success of any future control strategies,” warned Mel.

She pointed out that adding Defy into the pre-emergence stack had always improved overall efficacy and Black-grass control.

“With the aim to achieve 97% Black-grass control just to hold populations in check, growers and agronomists need to maximise performance at every point in an integrated approach,” she added.