Getting to grips with grass weeds It’s a well-known fact that grass weed control is a major problem facing UK farmers. Dominic Kilburn reports on the findings of a new survey which highlights how issues with weeds have forced unprecedented changes in farm management practices. According to the latest ‘National Grass Weed Study’ on average, growers spent £89/ha on their farm herbicide bill last year: 21 per cent of them spending between £100– £125/ha, 10 per cent spending between £125–£150/ha and 3 per cent over £150/ha. Comparing herbicide costs by cultivation type, the average spend on herbicides in 2016 from ploughbased systems was £74/ha, and £95/ha on a min-till based system – the latter seemingly more reliant on chemistry. In addition, 55 per cent of farmers sprayed off crops in 2016 due to grass weed infestations and, in these severe black-grass situations, average herbicide cost was £106/ha – that’s without factoring in the cost of the seed, fertiliser and first fungicides. That’s the stark reality of the problem facing farmers in the UK, highlighted Monsanto’s technical development manager, Barrie Hunt (left) who was presenting results from the company’s National Grass Weed Study undertaken in 2016, involving over 380 growers from around the UK. “There’s no doubt grass weeds in arable crops are the number one problem,” commented Mr Hunt. “If you look at the fact that resistant black-grass was first found in Essex, in 1982, and now most farms that have been sprayed with herbicides regularly have some level of resistance, then we’ve not been very successful in dealing with it,” he said. “There has also been a major decline in the performance of key herbicides over the years as well as a loss of products which has had an effect,” he added. “However, the issue is far more than just black-grass,” continued Mr Hunt. “Perhaps there has been too much of a focus on black-grass at the expense of other weeds such as
bromes wild oats and even couch. “How to control a mix of these weeds, and black-grass, is not easy,” he said.
Comparisons The first National Grass Weed Study was carried out by Monsanto in 2000, featuring 234 growers on 119,500ha (295,000 acres). The latest, 16 years on, included 386 growers on an arable area of 165,000ha (407,500 acres). Back in 2000 it was acknowledged by those in the survey that 34 per cent of their winter cereals area was suffering from black-grass problems, and 30 per cent was affected by wild oats. Fast forward 16 years and almost half the winter cereals area had black-grass as a problem (a 35 per cent rise), although difficulties with wild oats had fallen slightly. Brome and ryegrass problem areas had also increased by 72 and 55 per cent respectively during the intervening years. In line with this, 74 per cent of farms reported an increase in black-grass problems and 38 per cent of farms reported an increased problem with brome. Furthermore, 32 per cent of growers saw herbicide resistance as a “very serious or serious problem” when it came to managing blackgrass in 2000, and this figure leapt to 62 per cent in 2016.
Spray timings Looking at typical spray timings used to control black-grass in winter cereals and how they might have changed, in 2000 the vast majority (71 per cent of farms) were using autumn postemergence herbicides with only 12 per cent of farms using autumn pre-em products. “This was preAtlantis of course, when products like IPU and Lexus were in use, and only 16 per cent of farms were using post-em products in the spring,” commented Mr Hunt. “By 2016 there had been a huge swing to autumn pre-ems (84 per cent of farms) and a reduction in autumn post-em (45 per cent) on
Black-grass and grass weed problems in general have done more to shift farmers towards spring cropping than any agri-policy.
account of resistance, as well as much more use of stubble-applied sprays; 76 per cent of farms in 2016 compared with 29 per cent in 2000. “Spring post-em spray use had increased in prominence by 2016 (62 per cent of farms compared with 16 per cent in 2000) and this is probably down to growers attempting to catch up with other weeds at the same time,” he suggested. However, Mr Hunt added that those surveyed last year were almost unanimous is saying that without glyphosate, their weed control would be virtually impossible and that their cropping systems would be in serious doubt.
Cultural control choice Although the plough is making a comeback on UK farms, at least on a rotational basis, according to the National Grass Weed Study of 2000, 91 per cent of farms questioned said that the plough was one of the main cultural techniques to control grass weeds, 32 per cent spring cropping, 29 per cent stale seedbeds and just 15 per cent delayed autumn drilling. This compares with 63 per cent using the plough in 2016, but big
increases in the proportion of farms using spring cropping, stale seedbeds and delayed autumn drilling (81, 78 and 69 per cent respectively). “Cultural technique habits like delayed drilling take a long time to develop but it’s clear when you consider this change, and the increase in stale seedbeds and spring cropping, that growers are trying to get more and more weed control outside of the crop itself,” explained Mr Hunt. “Black-grass and grass weed problems in general have done more to shift farmers towards spring cropping than any agripolicy may have done,” he added.
Future changes To conclude last year’s study, growers were asked what were the main management changes they were considering to address current grass weed problems. Growing more spring crops (62 per cent of farms); improving stubble weed control (53 per cent); improving winter OSR weed control and drilling more winter wheat later (both 41 per cent) were some of the most popular considerations of 12 cultural control solutions. continued over...
Study Samples National Grass Weed Study 2000 Number of growers
Average arable area
Average winter cereals area
Winter cereals % of arable area
Plough-based winter cereals establishment
Reduced tillage winter cereals establishment
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Published on Aug 3, 2017