Bayer has extended the supply period of grass weed killer Atlantis (mesosulfuron-methyl-sodium + iodosulfuron-methyl) because the prolonged cold weather has reduced the opportunities for spraying.

Autumn applications were curtailed by wet weather causing a backlog of crops needing treatment this spring. But the cold winter meant conditions have only recently become suitable for applications, although blackgrass growth is slower than usual this spring.

Many growers will still want to apply Atlantis this month, Bayer says, so it has extended the normal cut off date for supply to 23 April.

The firm says responsible stewardship of Atlantis is critical, as delayed applications to mature grass weeds can compromise efficacy and possibly encourage the development of resistant populations on farms.

When active growth starts, priority should be given to applications to earlier drilled crops where grass weeds are more likely to be advanced, Bayer adds.

Later drilled crops or those that have received a more effective pre-emergence herbicide, such as Liberator (flufenacet + diflufenican), should then be treated. Where no subsequent emergence of grass weeds is anticipated this spring, Atlantis WG + Biopower is most effective when applied alone.

In a compressed spray season, growers have also been advised to avoid complex Atlantis tank mixes and pay attention to optimising application factors, such as spray quality and boom heights.