Weed Review highlights technology solutions for product losses

Over 80 delegates attended the 49th BCPC Annual Weed Review chaired by Dr Gordon Anderson-Taylor, Bayer CropScience, and held at PGRO, Peterborough on 24 October. The Review addressed technology solutions for product losses.

“Despite the various regulatory challenges, loss of herbicides and ongoing build-up of resistance to current products the presentations made at this meeting demonstrated a range of innovative approaches being taken to address all of these critical issues,” said Gordon. “Weed control remains one of the most important factors to maintain sustainable food supplies and our landscape environment, and whilst a somewhat neglected area for funded practical research, both researchers and the industry in general are clearly investigating and in some cases adopting new technological approaches in order to ensure that we can maintain adequate control of weeds in the future.”

Peter Lutman, Rothamsted Research set the scene by assessing the weather conditions affecting farming during the 2011/2012 season. Drought and poor performance from pre-emergence herbicides caused problems with weed control in the autumn. Although the spring started well, a cold, wet April meant early sown crops failed to grow and slugs were abundant. With cool wet weather continuing into June and July this affected crop growth and grain set.

Peter assessed current funded research projects on weeds and weed control. “Only a very few substantial projects are now being carried out, funding is limited, there is no long-term strategy for projects and about 30% is short-term work being done by PhD students,” he said. “It is now time for us to consider how we get more strategic funding into weed research.”

The review then considered a completely different approach to weed control in oilseed rape with the recently introduced ‘Clearfield’ Production System. “Here we use high yielding herbicide tolerant hybrid seeds which have the ability to resist certain herbicide modes of action not otherwise used in rape,” explains Jon Williams, BASF. “Rather than a pre-emergence / post-emergence programme, this programme uses one application of a metazachlor plus imazamox product plus an adjuvant, post-emergence up to growth stage 18.”

“This has great benefits as it shifts the timing of application away from the really busy time on farm, it also plays a key role in good establishment of oilseed rape,” says Jon. “More importantly, it targets emerged weeds and offers excellent control with the broadest weed spectrum, including cruciferous weeds, compared to current herbicide standards. It is critical that the metazachlor plus imazamox product is only used on Clearfield hybrids and it is also important that best practice is adopted in rotational management to minimise seed losses.”

There is concern over the potential risk of water contamination from some key active ingredients for weed control in oilseed rape. Ron Stobart, NIAB TAG, outlined a project that evaluates a new approach using carefully-directed control methods between crop rows. Using simple shielding and guidance systems plots were treated inter-row with glyphosate using a narrow nozzle. Trials were also done integrating inter-row treatments with an over-row selective application. This delivered excellent weed control between and within the rows with little or no crop damage. “The results have been encouraging and no impact on yield has been seen in our studies,” says Ron. “We now need to look at width of equipment and speed of application. This is an alternative approach of controlling weeds in oilseed rape which could well be considered for other products used inter-row.”

Bracken covers an area of about 1.5m ha in the UK. It causes problems not just to agriculture by taking out grazing, but it also obstructs footpaths, harbours ticks and disease and creates a monoculture threatening biodiversity. The bracken’s underground extensive rhizome system is the biggest problem, sending up new fronds. “The current control system comprises a two-stage process,” explains Simon Thorp from The Heather Trust. “Primary control is to spray asulam by helicopter with a follow-up treatment using hand lances in the second year. Asulam is unique in terms of its selectivity for bracken and that it can be sprayed from the air but due to concerns about the impact on water and the environment it failed to gain approval after appeal in September 2011 – the end of the use-up period is 31 December 2012.”

“Leaving bracken to run rampant is just not an option,” says Simon. “Alternative control options are ground based spraying; weed wiping; cutting; crushing; low level equilibrium grazing and biological control methods but asulam has always been very effective in providing long-term control. We hope that the formation of The Bracken Control group will help raise awareness of the threat posed by bracken and that there will be sufficient support to enable the continued supply of asulam products from the start of 2013 until re-registration of the product can be achieved in the future.”

2011/2012 has been a particularly difficult season with thick stands of black-grass being seen around the country. Lack of control has been attributed to tough environmental conditions and increasing resistance. “The bad news is that resistance does not go away,” warned Richard Hull, Rothamsted Research. “The good news is that there are things that can be done. Delaying drilling for example has been shown to give a 39% reduction in black-grass plants. Results from spring cropping are even more significant, reducing plant numbers by 88%. The main thing is to assess your black-grass problem and know what works on your farm”.

A session on bio-herbicides concluded the Review. “We have an interest in finding bio-rational solutions for controlling weeds between rows and in organic pre-planting/drilling weed management,” explained Emma Garrod from Produce World, leading grower of fresh vegetables. “Hand weeding options are very labour intensive and costly so engineering application systems and bio-herbicides are the best solution for our farming business.”

Lynn Tatnell, ADAS Boxworth went on to explain a new research project SCEPTRE (Sustainable Crop & Environmental Protection – Targeted Research for Edibles). “The aim of the project is to fill the gap from the loss of actives, identify crop safe actives and develop sustainable integrated pest management systems,” explained Lynn. “We found that perennial weeds are particularly challenging to bio-herbicides; however, from the pot work trials, one or two products look very promising. We will extend the work into field trials next year with repeated applications and also look at bacteria based products and mixtures.”