Delayed pre-emergence sprays might not be too much of a problem, particularly when it comes to controlling broadleaved weeds this season, Interfarm UK has told growers.

Trials found that flumioxazin applied early post-emergence at 100ml/ ha when weeds were between the one and three leaf stage gave 100% control of charlock, chickweed, fumitory, groundsel, field pansy, red deadnettle, ivy-leaved speedwell and mayweed.

That rate and timing also controlled 99% of cleavers, common field speedwell and Shepherds purse and 98% of poppy.

“Flumioxazin also gave up to 90% control of annual meadowgrass, 80% control of ryegrass and 65% control of blackgrass, applied early post-emergence,” said Interfarm’s David Stormonth.

He suggested growers waited until weeds had 1-3 leaves before applying flumioxazin (as in SumiMax), rather than applying a pre-emergence herbicide in less than optimal conditions.

“Ideally the soil should be moist. As is the case for most pre-emergence herbicides, it is best to avoid soft or lush crops, waterlogged crops or crops under stress. The use of a tank cleaner is recommended after spraying.”

In bad blackgrass situations, he said flumioxazin was best applied early post-emergence when the weed had 1-2 leaves.

“Here it can be mixed with other partner herbicides such as Liberator (flufenacet and DFF), Defy (prosulfocarb), chlorotoluron or IPU. It can then be followed up by Atlantis (mesosulfuron-methyl and iodosulfuron-methyl-sodium) later in the autumn. Alternatively it can be used with Lexus (flupyrsulfuron-methyl) early post-emergence.”