Focus on cereals, still to early for oilseed rape

Prioritise applications of Atlantis to winter wheat rather than worrying about Kerb on oilseed rape, says NIAB TAG’s Ben Freer.

Current soil temperatures favour Atlantis WG (mesosulfuron and iodosulfuron) and Broadway Star (pyroxsulam and florasulam)/Broadway Sunrise (pyroxsulam and pendimethalin) for sterile brome whilst the residual effect of Kerb (propyzamide) greatly diminishes when it is applied in the same situation.

"We have perfect conditions for Atlantis," says Ben Freer, regional technical agronomist at NIAB TAG. "The black-grass has flushed through and is growing actively. Atlantis is most effective on small weeds with two to three leaves and, with most black-grass at this stage now, growers need to get out there and tackle it.

"Well-made applications of Atlantis, partnered with the appropriate residual, will be very effective against black-grass and other problem grass-weeds if made under current conditions.

"Conversely, Kerb is far more effective when the soil cools to around 8°C. The half-life at this temperature is double that at 15°C," Mr Freer explains.

"Today soils are around 13°C to 14°C and it will be about three weeks before the soil temperature is low enough for growers to benefit from the full 120 days half-life.

"This product needs time to penetrate the soil profile to reach the grass-weed root zones. It starts to degrade the moment it touches the soil surface.

"If growers are to make the most of the herbicide, they need to ensure that sufficient active ingredient reaches the root zone.

"I strongly advise growers to wait. The frost this weekend shows that the weather is turning but the soil acts a buffer and takes time to cool," says Mr Freer.

"In order to get the most out of the herbicide it is of vital importance to spray in the right conditions. This may be particularly galling if you were planning to tank mix a fungicide as this should be applied now and will mean a separate pass through the crop."