Clethodim trial demonstrates importance of stewardship guidelines

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A field trial has demonstrated the importance of stewardship guidelines currently in place for graminicide clethodim.

The guidelines were devised several years ago, to support best use and product performance when the product is applied to winter oilseed rape to control weeds such as blackgrass.

UPL has continued to evaluate the stewardship, altering it in accordance to the latest science and findings from annual trials, with the most recent changes taking place prior to last year’s season.

The latest in a series of independent trials has since taken place to further explore the potential outcomes when adhering or not adhering to the stewardship, demonstrating the impact of variables such as application timing and tank mixing.

Technical specialist & arable herbicide lead at UPL UK & IE, Rob Adamson, said: “The clethodim oilseed rape stewardship scheme has evolved over the past few years, after originally being created to minimise the risk of phytotoxicity at stem elongation.

“The purpose of this latest field trial was to demonstrate the importance of changes that were made to the stewardship in 2018, which included reinforcing the application cut-off date of October 15.

“To do so, we investigated the impact of clethodim applications on OSR, both inside and outside of stewardship to varying degrees to observe potential crop damage, as well as the effect of tank mixing, which isn’t recommended.

“The results have proven that the stewardship does offer the optimum guidance for applying clethodim, and application outside of this could result in varying levels of phytotoxicity at stem elongation.”

The application cut-off date considers the declining average daily temperature, slowed crop growth, larger crop growth stages, and the increased chance of frost, to mitigate the highest risk scenarios for phytotoxicity.

The stewardship also recommends that product efficacy is optimised through using a water conditioner, although clethodim should not be mixed with other products, including adjuvants. The trial showed that water conditioner does not have an impact on phytotoxicity.

Mr Adamson added: “Clethodim is a highly effective product for controlling grass weeds, particularly when used following a post-emergence graminicide such as quizalofop-P-tefuryl.

“This approach reduces the competition from cereal volunteers, to allow the blackgrass to actively grow and reach the three-leaf stage, which is when clethodim is most effective.

“With growers having fewer blackgrass control options due to resistance, it’s vital that the products that remain are used effectively in adherence to recommended stewardship, and as part of a wider, programmed approach.

“This includes following up with an application of an alternative mode of action, such as propyzamide or carbetamide.”

Clethodim is the active ingredient of Centurion® Max by Arysta LifeScience, now part of UPL. For more information including the complete stewardship document, visit


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