Get herbicides on early while weeds are small, but ensure they're growing before you spray. That's the clear message from agronomists and industry experts as the spring herbicide campaign gets under way.
Almost three-quarters of the blackgrass area is still to be treated, after high dormancy and cold, wet conditions prevented autumn applications, so there will be more need than ever to get spring treatments right, Velcourt's Keith Norman says.
"Conditions weren't right for Atlantis last autumn, plus we saw very slow blackgrass germination. By March most should be up and we've generally seen good control at this timing on our farms. But the weather's got to be right and weeds have to be growing."
Oxfordshire-based Nick Brown of ProCam estimates just a quarter of the blackgrass area was treated at the preferable autumn timing, despite many having bought the product early. He urges growers not to leave Atlantis sprays too long. "I've got a few growers who've sprayed already, as crops and weeds grew very fast in January. Some crops already look like they do in March.
"The ideal would be to leave it [Atlantis] until the end of March or early April when it's warm and everything's growing, but the chances are blackgrass will get too big and sprays will suppress the weed, not kill it. You really need to hit blackgrass before it stops tillering," he says.
Protracted germination could mean weeds in some early-sown fields are bigger than that before growers get a chance to spray, he warns. "You really need to be spraying as soon as conditions allow."
Give soils time to warm up properly before rushing on with Atlantis, Velcourt’s Keith Norman (right) says, pictured here with Paul Cartwright.
Soil temperatures are key to maximising efficacy and generally have to be above 6C for Atlantis to work well, Mr Norman explains. Weeds also need a decent period (7-10 days) of milder weather after any cold snap to start growing, he says. "If you're on heavy soil, air temperatures may be high, but soils are likely to be some way behind."
David Parish of The Arable Group agrees. "The other thing to remember is that any waterlogged areas will take a lot longer to warm up. There's always a tendency to go on with Atlantis at the first spray opportunity, but that might not be the right thing to do - you've got to make sure blackgrass is actively growing."
Where blackgrass pressure is very high and growers want added security in less favourable conditions, he suggests tank mixing Atlantis with full-rate Hawk (2.5 litres/ha). "It's the Rolls-Royce approach and will probably add another £14/ha on top of Atlantis, but it will buy a bit more robustness." In low pressure situations, Hawk, IPU, or Lexus could be used instead of Atlantis, he suggests.
Mr Norman reminds growers that the limit of one sulfonylurea per season and increasing concerns around Atlantis resistance means they should do everything they can to make sure all factors are favourable for Atlantis to work.
Meadowgrass
Early treatment is also important for getting on top of annual meadowgrass providing conditions are right. "You're best going when it's small, at the early tillering stage," says Bayer CropScience's Gary Jobling. "Really you've got to spray before three tillers of the weed. But, as with blackgrass, you have to be mindful of the weather and growing conditions."
Mr Parish says most meadowgrass in his Bedfordshire region was treated with an IPU-based spray in the autumn, with reasonably good results, so there is little AMG pressure this spring. "Residuals are still the best against meadowgrass," he comments.
But once IPU is banned, meadowgrass control is going to be more expensive and will require more thought, Mr Jobling says. "Growers have to realise that a lot of the alternative products [see Cereals panel] don't have the spectrum of IPU, so have to be targeted better." They are also more expensive than traditional IPU-based mixes. "You're probably looking at another £7-10/ha more for most post-em treatments," he says.
Brome
If brome is your main focus, then like blackgrass and meadowgrass, early treatment could be best. A Velcourt trial for Bayer CropScience near Castle Howard last year found applying Atlantis and Pacifica at the start of February gave around 95% control. This compared with nearer 52% and 72% respectively at the later 14 March timing and around 30% for both products at the 3 April treatment date.
"The brome was small (three-leaf stage) and was growing, so we'd expect decent control from the early timing," Mr Jobling explains. "But it's not a timing growers would normally be looking at."
Most would probably look to control brome from the beginning of April onwards, in an attempt to pick up other weeds at the same time, he says. "But you have to know what your main focus is. If it's brome, you need to go while weeds are small and growing. As soon as brome gets to stem extension, efficacy will be seriously knocked back."
Monitor and Attribut were also tested in the trial. Both work best at higher temperatures, so performed well at the later (warmer) 17 April timing. "Attribut was the best product at this timing, but still didn't hit 50% control, highlighting the importance of getting on early," Mr Jobling says.
"Monitor or Attribut can also be used, but you're only allowed one SU per season, so if you go with either of these, you can't use Atlantis or Lexus," notes Mr Parish.
Poppies were also present at the Yorkshire trial and the best control came from using Pacifica later in April (89-99%, based on visual assessments).
IPU and trifluralin alternatives at Cereals
Still undecided what to use when IPU and trifluralin are gone? If so, a trip to Velcourt's stand at this year's Cereals event (11 & 12 June) at Leadenham, Lincolnshire could be time well spent. A number of pre- and post-em treatments for blackgrass and annual meadowgrass are being trialled.
In the (non-resistant) blackgrass trial, pre-ems centre around 2.0 litres/ha Defy, with various partner products - namely Stomp, Crystal and Liberator. "We're using a pre-em only to highlight the longevity of products. Blackgrass came up well and so far they've all worked quite well," Mr Norman says. Post-ems are based on Atlantis + biopower, with different partners to see whether they provide anything extra against this season's protracted germination.
For the pre-em meadowgrass trial, combinations of Defy, Hurricane, Graduate, Bullion, Liberator and Crystal fall under the spotlight, while post-em options include Bayer's new Othello and Sumimax - a new product from Interfarm UK.
"Othello will be launched officially at Cereals, although a small amount was available commercially last year," notes Mr Jobling. "It has autumn approval and will hopefully help fill the IPU/ trifluralin gap. But it is expensive compared to what growers are used to - you're probably looking at around £30/ha for the whole treatment."
The product is purely for annual and rough stalked meadowgrass control and should not be used for other grassweeds, he says. "It hasn't got as much active ingredient as other products, so could just add to resistance pressure."