Applying a contact plus residual herbicide mix two to three weeks after planting is the most effective way of controlling annual meadowgrass in potatoes, Scottish Agronomy trials suggest.
“Post-emergence options are very limited so the main thing is to go early,” says the firm’s Eric Anderson. “Allow the ridge to settle and time the spray when the largest sprouts are still 2-5cm below the soil surface. Growers with large areas to cover need to start as early as possible to avoid getting caught by the weather.”
On heavier soils weed control should be straightforward using either metribuzin or Artist-based programmes, he says, based on trials carried out last year and the advisory team’s recent experiences.
“But in challenging annual meadowgrass or cleavers situations, the flufenacet component of Artist adds the extra residual activity needed,” he says. Adding 1.2 litres/ha of a 500g/litre formulation of linuron will also boost control.
But growers must take account of varietal and soil type restrictions, when using metribuzin-containing products, including Artist, he stresses.
Annual meadowgrass growth stage is the main consideration when choosing a contact herbicide partner, Mr Anderson says. “For small meadowgrass, 2 litres/ha of diquat should be sufficient. If it has reached three leaves, reduce the rate to 1.5 litres/ha and mix with Shark, or for the strongest meadowgrass control, use Harvest at 2 litres/ha, provided you are confident of getting six hours’ drying time post-application.”
Artist – flufenacet + metribuzin
Defy – prosulfocarb
Harvest – glufosinate-ammonium
Shark – carfentrazone-ethyl