Complex tank mixes could reduce herbicide efficacy and compromise blackgrass control, according to Bayer CropScience.

Recent cold weather has delayed many spray programmes and growers keen to catch up when conditions improve should be wary of over-complex tank mixing, said the firm’s agronomist, Ron Graham.

“Delayed spray operations has compounded the pressure on tank mix decisions so, not surprisingly, many growers would like to combine a variety of inputs in one application.”

But, Bayer’s Atlantis (mesosulfuron-methyl + iodosulfuron-methyl) can be 2-3% less effective when used in a complex mix, he said.

This not only leads to more blackgrass surviving, but also increases the risk of resistant weed survivors, which will be returned to the soil next season, he warned. He advises against complex mixes, particularly in difficult weed situations or where applications are delayed.

“It is essential to apply Atlantis as soon as possible, but growers must avoid the temptation to apply immediately after an extended cold period as grass weeds may not be actively growing.

Bayer recommends applying Atlantis at 400g/ha, together with the adjuvant biopower.