Hit black-grass hard in OSR

With such high levels of black-grass in oilseed rape crops this autumn, growers are being advised to use the most effective herbicides in sequence to get on top of the grass-weed.

Adopting an approach to tackling this weed in oilseed rape as is done in cereals will lead to more consistent and better control, whilst also protecting the valuable actives that we have left in our current herbicide arsenal, says Don Pendergrast, product development manager for Arysta Life Science.

Don Pendergrast.

“It is essential to control black-grass at all stages of the rotation, pre and post drilling where possible – the battle needs to be fought at every stage in the whole rotation. Ensuring that the levels of control in oilseed rape are as good as possible, is key to this.”

Three years ago the herbicide Centurion Max, was launched onto the market; Centurion MAX contains 120g/L clethodim formulated as an emulsifiable concentrate . It was recommended for use post-emergence in winter oilseed rape and sugar beet to control black-grass, annual meadow-grass, other grass weeds and cereal volunteers.

“In many situations, growers will find themselves coming around to using the product again in the same place in their rotation and it is critical that they are fully aware of how to get the best of the herbicide for the best black-grass control possible, and also to fully understand the stewardship of the product which means how to use it as part of an anti-resistance programme,” he says.

The ‘dims’ are a group of actives that are affected by ACCase target site resistance in black-grass.   Although clethodim is a ‘dim’ it has proven itself to be more effective against resistant black-grass than other herbicides of the same class, such as tepraloxydim (Aramo) and cycloxydim (Laser), says Stephen Moss, weed expert.

Consequently, Dr Moss says that even growers who know they have ACCase-resistant black-grass populations shouldn’t be put off using the product as it can still improve control.

“A worldwide research review considered clethodim to be the lowest resistant risk ACCase inhibiting herbicide, with only two of the 11 know target site mutations conferring high resistance to it.”

Dr Moss points out that its relative efficacy in the field is likely to be strongly influenced by the dose used, weed size and time of use.

Clethodim is likely to be best used in sequence with non-ACCase inhibiting herbicides, such as propyzamide, which is unaffected by herbicide resistance, he says .

“In addition, use of clethodim should be integrated with non-chemical control methods, used throughout the crop rotation, to reduce reliance on herbicides and reduce the risk of further evolution of resistance. “

Centurion Max is extremely good on a range of grass weeds such as annual meadow-grass, rye grass, wild –oats, brome and cereal volunteers in winter oilseed rape and sugar beet, but its strength is that it is providing good control of black-grass, says Dr Tudor Dawkins, technical director for ProCam.

“In practical terms it should be the black-grass stage which governs the application timing; however he advises growers who have high black-grass populations to use Centurion Max early in the programme when the oilseed rape has reached the 2 – 3 true leaf stage. The blackgrass should also be around the 2-3 leaf stage, to get the optimum efficacy.

It is important to follow up with products such as propyzamide, as part of the programme, to complete the black grass control programme and to protect the product from undue selection pressure and resistance development.

“Since its launch we have got better at using Centurion Max in the stewardship context and this is helped by its compatibility with products that are being applied at the same time, such as insecticides for Cabbage Stem Flea Beetle.”

“We have found that using a water conditioner with Centurion Max improves the benefits, and this is an approach that I would advocate this autumn. It will also be necessary, in some areas, where there is strong pressure from cabbage stem flea beetle, to include an insecticide.”

• Centurion Max should be applied at a dose rate of 1 L/ha in 200-400 litres of water and at a fine or medium spray quality.
• In winter oilseed rape it can be applied from the 2 true leaf stage and in sugar beet from cotyledon stage.
• One application can be applied per crop and the latest time of application in oilseed rape should be before the end of October.
• Avoid later applications (after mid October) to earlier flowering or maturing varieties of oilseed rape (6 or above)
• Avoid later applications (after mid October) to crops drilled on or before 25th August and in sugar beet before row closure.
• Centurion MAX has no LERAP.