Grassweed killer Atlantis (mesosulfuron-methyl + iodosulfuron-methyl-sodium) may have greater residual activity than competitor Lexus (flupyrsulfuron-methyl), according to trials by Bayer CropScience, in direct contrast to the commonly-held view in the industry.

But the firm’s Gordon Anderson-Taylor says the results are not a reason for growers to avoid tank mixing a residual partner with either product.

“Both Atlantis and Lexus are only moderately persistent, so there is still a practical requirement for residual partners to provide acceptable levels of control of blackgrass germinating after application.”

In the trials carried out at three sites, crop and blackgrass were sprayed off with total foliage killer paraquat at three timings during the growing season before pre-emergence application of both products.

“The results show Atlantis having greater residual efficacy than Lexus.”

October applications of Atlantis gave on average 72% control compared with 37% for 20g/ha of Lexus, and 45% for the higher 40g/ha rate.

Other timings gave similar results, albeit with less germination of grassweeds after initial burn-off, he says.

“A TAG trial last season also gave similar results, which supports the data we’ve generated.”

DuPont’s Neil Morey says his firm has not done similar trials work.

“But our customers have seen good residual activity from Lexus and that’s one of the reasons why we have been able to get a pre-emergence barley recommendation for flupyrsulfuron-methyl.”