Loss of useful chemistry creates control challenge

Weed control costs are likely to increase following news that IPU and trifluralin are to be banned within the next two years. Agronomists, growers and manufacturers fear the loss of these two cost-effective actives will also present real challenges for managing herbicide resistance.

IPU has provided growers with a relatively inexpensive, and initially effective weed solution for decades,” says Masstock’s Clare Bend. It offers a useful complimentary mode of action against resistant blackgrass, and its loss will put more pressure on products like Atlantis (mesosulfuron-methyl + iodosulfuron-methyl-sodium) something that has been compounded by the loss of trifluralin, she says.

That’s a cheap active that goes well with flufenacet-based pre-emergence products, such as Crystal or Liberator, she says. “As an add-in, it’s maybe brought an extra 20% blackgrass control at the pre-em timing, which reduces the selection pressure on following products.”


  • IPU and trifluralin both likely to be withdrawn by mid-June 2009

  • Alternatives are more expensive

  • Trifluralin loss reduces resistant blackgrass options and increases pressure on remaining actives (particularly Atlantis)

  • IPU alternatives for annual meadowgrass control are more expensive

  • Spray timing flexibility will be reduced

  • Limited alternatives to trifluralin in brassica and vegetable crops


Dow AgroScience’s James Knight says losing IPU and trifluralin creates a major challenge for effective grassweed control, particularly because trifluralin is effective against resistant blackgrass. “No wonder almost 750,000ha of UK crops were treated with trifluralin in some form last year.”

Winter barley growers will be particularly hard-hit by the loss of IPU and trifluralin, as the choice of chemistry for blackgrass control is very limited, Ms Bend notes. “The flufenacet followed by IPU sequence has been performing very well, and in very bad blackgrass situations, we’ve been able to add in some trifluralin. Once trifluralin goes, we’ll be left with flufenacet, pendimethalin, flupyrsulfuron and struggling to perform fops/dens. We still have chlorotoluron, but this has varietal limitations.”

Frontier’s Brian Ross says the IPU ban will have significant implications for meadow grass control. “IPU has lost its value as a blackgrass product, but it’s an extremely cheap way of controlling meadow grass in winter crops.” There are other effective alternatives such as Crystal or Liberator, but they are more expensive, he says.

Trifluralin’s removal will have a big impact on minor crops and vegetables, he adds. “Treflan is the mainstay in many vegetable herbicide programmes, and most of the other options are based on off-label approvals only.”


South-west barometer grower Troy Stuart (pictured below) says losing IPU and trifluralin will be a major blow. “We do have some alternatives but none that offer the same value for money.”

His agronomist, Howard Moore, estimates that meadow grass control cost could increase by 30% and says the logistics of when to spray could become more complicated.

“It will force people into more expensive pre- or late post-emergence options and there will be much less spray timing flexibility.” The biggest impact will be on meadow grass and mayweed control, but the loss of trifluralin also removes a useful anti-resistance blackgrass option, he notes. “It’s also still useful in oilseed rape.”

John Hutcheson uses both IPU and trifluralin in the autumn and is concerned that product choice will become more difficult. “Our agronomist reckons we will use Firebird with DFF, but there is a potential weakness against mayweed. That may need a further application of another product in the spring – so much for reducing chemical use!”

IPU has not been an effective blackgrass herbicide on Ben Atkinson’s Lincolnshire farm for some time, but he will miss it. “I do have odd fields I can get away with using it.”

He was not surprised by the decision to ban IPU, but says it should be used to the industry’s advantage. “We have known about IPU levels in watercourses being unacceptable for some time. We must turn this into a positive and inform people of the positive environmental effects modern agriculture is delivering.”

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