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The chemical toolbox is only part of the story for successful ryegrass management, says Rob Adamson (pictured above).  “Success is judged on the number... Cultural controls help get most from herbicides

The chemical toolbox is only part of the story for successful ryegrass management, says Rob Adamson (pictured above).  “Success is judged on the number of grass ears and subsequent seed return in the summer,” he adds.

Preventing any ryegrass weeds that successfully establish from tillering too heavily is essential to the protection of subsequent crops. This comes down to ensuring the current crop is as competitive as possible.

Seedbed preparation, crop nutrition and drilling date all important considerations, says Mr Adamson. “The protracted germination of ryegrass means that, unlike in a blackgrass situation, delayed drilling is not as useful.

“Although this tactic will still give an opportunity for a stale seedbed to be established, it could be counter-productive if the crop is drilled too late, as this would allow competitive ryegrass plants to overpower the weaker and thinner wheat seedlings.

“Thankfully, recent weather conditions mean there’s good soil moisture available this year, which means there should be the opportunity for growers to remove the first flush of ryegrass and to drill wheat into a clean seedbed.

Any subsequent weed growth should then be nearer the pre-emergence application.

“In the worst affected regions, it will make sense to use cinmethylin – the strongest active – pre-emergence to get ryegrass control off to the strongest possible start.”

DNA loops provide blackgrass resistance clue

Scientists say a new discovery could help explain why blackgrass can rapidly develop resistance to herbicides.

Blackgrass prevalence is largely due to widespread multiple-herbicide resistance. Now a study has shown that whether blackgrass will become herbicide resistance depends on more than its chromosomes.

Working with researchers at Clemson University in the USA, scientists form Rothamsted Researchers have found that the weed contains small loops of DNA that are outside the plant’s chromosomes.

Genetic structures

These loops, called extra-chromosomal circular DNA, are not inherited in the same way chromosomes are. Instead, they evolve separately from the main genetic structures in the plant and could explain how blackgrass quickly develops resistance.

Compared to blackgrass that are herbicide sensitive, the DNA loops of herbicide-resistant blackgrass have extra copies of genes known to confer herbicide resistance, including genes related to herbicide detoxification, says Dana MacGregor, who was part of the Rothamsted group.

“These [loops] may contribute to the genetic diversity we see in blackgrass and explain how it has adapted to man-made and abiotic stresses, including herbicide treatment,” she explains.