At the 46th BCPC Annual Weed Review, held at the PGRO, Peterborough on 4 November 2009, a clear message was given – “there are no existing cultural control methods which can fully compensate for the loss of cereal grass weed herbicides, resulting from the lack of new products coming forward, and the removal of key products by EU legislation. But there are methods which can support the performance of products that are still available.”
In a review of work conducted over the last forty years, Dr Peter Lutman and Dr Stephen Moss of Rothamsted Research revealed that, in general, cultural control was less effective, more variable and more expensive than using herbicides. For example, the most effective agronomic practices can only achieve 70% to 80% control of black-grass – compared with 90% control given by the best herbicides. However, the more effective cultural practices can help to control grass weeds, even with a depleted range of chemicals.
"Using appropriate cultural practices can take the pressure off herbicides,” said Dr Lutman. “The current techniques of; non-inversion tillage, early planting, very low crop seed rates and continuous winter cropping, all put huge pressure on herbicides. This approach will not succeed in the future when fewer products are available, and if grass weed resistance becomes more of a problem than it is today”.
Major adjustments will need to be made in farming practices including, for example, rotational ploughing and spring crops in the rotation. “If we do not change the way we grow our cereals, we run the risk that they will be overwhelmed by unmanageable grass weeds in the not too distant future” said Dr Lutman.
Mark Ballingall, Senior Weeds Consultant at the Scottish Agricultural College (SAC) demonstrated the significant impact that the EU91/414, Water Framework and Drinking Water directives have on weed control in potatoes. Reduced rates of linuron and metribuzin – used on 66% and 26% of the crop area respectively – and the absence of new pre-emergence products to substitute them, could result in 10% yield losses, costing the industry £100m per annum. “A move to post-emergence products will not be helpful – bentazon will also be deregistered, and the one remaining post-emergence product, rimsulfuron has limited weed spectrum and cannot be applied to seed crops,” said Dr Ballingall.
"The results of the studies reported at this year’s review are further evidence that the EU Commission’s claims – that new chemical products, or non-chemical methods, will make up for the loss of key crop protection products – are misleading, certainly in the all important area of weed control” said The Arable Group’s (TAG) David Parish, chairman of the Review. “It is clear that major changes will need to be implemented; including a significant increase in cultivation operations. As was shown at the 2007 Weeds Review, by Drs. Wilson and Sparkes from Nottingham University, these can dramatically increase both the carbon footprint and costs of cereal and especially potato production”.
BCPC, in cooperation with other agricultural and horticultural organisations, will be holding a series of workshops during the next two years to address the problems resulting from the raft of EU legislation. “These will bring together all interested players; regulators, advisors, researchers, levy board representatives and agronomists to act in a concerted fashion” said BCPC Chairman Dr Colin Ruscoe. “They will investigate the full range of possible actions to find ways for farmers and growers to meet the challenge of increasing food production by sustainable intensification, despite the loss of key herbicides and other pesticides”.