Northern farmers learning from the south

Northern growers seeking southern knowledge was the theme at an open day exploring grass weed control in the light of advancing resistance held in Yorkshire by Bayer CropScience.

More than 50 growers and agronomists came to Stockbridge Technology Centre to hear Stephen Moss give a comprehensive overview of the speed and spread of resistant weeds. Dr Moss revealed that both enhanced metabolic resistance (EMR) and target site resistance in black-grass and rye-grass had increased since 2002.

Different types of target site resistance affect fops/dims/dens and the sulfonylurea type herbicides and that tends to be herbicide specific, but confers a high degree of resistance. In contrast enhanced metabolism affects many herbicides, but tends to confer only partial resistance.

The key point is that, regardless of the type of resistance, it tends to increase steadily leading to a progressive decline in herbicide efficacy. It is important to detect it early, while more options are still available, rather than delay until a catastrophic failure has occurred.

’To deal with it, growers in what have been traditionally ’easy’ areas for weed control will have to get used to greater use of pre-emergence applications of more robust actives based on flufenacet. Flufenacet is the pre-emergence herbicide least affected by resistance so it is important to use it at full rate.

’Such a strategy will help control most black-grass,’ he said. The aim must be to achieve over 95% control of black-grass, and this will become increasingly difficult as resistance increases. Thus it is essential that herbicide use is integrated with non-chemical methods to improve the overall level of control.

’I’d like to learn from experiences in the South,’ says Richard Hinchliffe, farming at Goole, Yorkshire. ’Nearly a third of our farm already has tricky black-grass and this issue is going to get worse unless we address it.

’Stewardship of chemicals is crucial, but it’s the whole package that matters - from creating a fine yet consolidated seedbed, through to boom stability, the only way to get the control is through paying attention to the details.

’I couldn’t believe the variation in control that Dr Moss’s results showed on cultural control. Ploughing for example, achieved 96% control in some cases but in others brought 20% more seed to the surface.

’Obviously the weather has a huge role to play in the success of these methods but it showed how important it is to know the history of the field and the seed bank that lies under the surface.

’The farm we recently took over had a huge problem so we decided to take the hit of spring cropping for a couple of years, but it is simply not economical, the land is just too heavy. Our aim is to achieve a sterile seed bed, so we are now using a winter bean break crop alongside delayed drilling and high seed rates.’

When subjected to Dr Moss’s test, these measures proved effective, achieving 82% and 53% reductions in grass weeds.

Concluding the day was the weed screen, a feature that is building quite a reputation for Bayer CropScience. For Mr Hinchliffe, it inspired him to try pre-em stacking on fields harbouring the most black-grass.

’This year we are going to add something to Liberator to get that lst 5-10% control,’ he says. ’It’ll either be diflufenican or pendimethalin. Although the weedscreen showed how effective Liberator and Kula (diflufenican and cholorotoluron) are, it can antagonise an autumn Atlantis WG (mesosulfuron and iodosulfuron) application, something which is already a struggle with the weather at that time of year but crucial in tackling the most awkward black-grass.’

’Elsewhere in the weed screen, the importance of timing for both pre- and post-emergence products was clear to see,’ remarks Gordon Anderson-Taylor, herbicides development manager for Bayer CropScience. ’When Liberator was applied at peri-emergence or at early post-emergence rather than the recommended pre-emergence timing, control was reduced allowing surviving plants to get away and set seed.

’Atlantis WG, biopower and Stomp (pendimethalin) applications at before the one leaf stage of grasses proved too early; all the weeds had not emerged but the spring applications demonstrated the loss of activity as a result of being too late,’ he points out.

’In this location the mid November application achieved good control, demonstrating the need for growers to look for suitable spray windows during the autumn period.’

Diflufenican also proved to be a crucial way to deal with sterile brome, with Liberator having the edge on Crystal (pendimethalin and flufenacet) in tackling this surprisingly difficult weed.