Grass weed yield culprits 'named and shamed'

The dramatic effect of heavy grass weed infestations on cereal yields is highlighted in new trials results this month, a timely reminder to any growers still making up their minds about autumn herbicide programmes.

Technical manager at Masstock Arable, Clare Bend, named and shamed the worst culprits when discussing herbicide strategies during a 'podcast' for Bayer CropScience.

"The enormously competitive nature of grass weeds in a cereal crop is well-known," she said, "but we were surprised by the results from our latest trials.

"Untreated black-grass infestations produced a 50 per cent yield loss, while failure to control rye-grass resulted in a 90 per cent yield loss.

"Even annual meadow-grass showed its ability to wreak havoc, delivering a yield loss of between 20 and 30 per cent," she added.

Ms Bend said the figures, collated from among the 23,000 different trials conducted by Masstock last year, provided adequate proof of the importance of tackling grass weeds early in the season.

"All our grass weed trials are being taken to yield so that we can demonstrate the short-term economic effects of different control policies," she explained. "For example, use of a pre-emergence herbicide delivered on average 40 more wheat ears per square metre compared to plots where no pre-em was used.

"Such figures could be very significant in slug-damaged crops or those sown at low seed rates," she noted.

"Moreover, by using a pre-emergence herbicide you reduce the number of black-grass plants exposed to the post-emergence treatment by a massive 80 per cent. That's good news as far as resistance management is concerned, because you're using AIs at the pre-em timing with less of a resistance issue."

Ms Bend advised growers to be careful with the timing of applications. Pre-em timing, she said, was critical because of low dormancy in black-grass this season - in some OSR crops it was already at the three-leaf stage - so growers must aim to 'get on ASAP' after drilling.

"The greater concern is that black-grass will be further on by the time we get to winter," she pointed out, "which should serve as a warning to those who sprayed Atlantis in the spring last season, despite their good results.

"In the spring, the target may be a tillered black-grass plant which could be harder to kill. It's paramount that growers go by black-grass growth stage and weather conditions, rather than calendar date. Remember that the weed must be actively growing."