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putting down protection to each new leaf as it emerges to avoid getting into a curative situation,” continued Mr Bailey. “I’m not saying T1.5 should become a routine spray; besides, on many units this may not be practically possible due to the spray days available, but risk factors on farm should be considered, such as varieties being grown, location and weather for example.

“But if septoria is the driver and you choose a T1.5, I wouldn’t use any other product than a multi-site which will protect leaf 2 until the T2 timing,” he advised. “If rust is a threat then consider a strobilurin for protection at that timing, and if rust is already active then add in a triazole for curative control as there is no other option.”

Is T1.5 justified? Septoria trials in 2017 with wheat

variety Consort demonstrated that when Arizona (folpet) was applied at T1.5 – as part of a T0, T1 and T2 programme, there was a marked improvement in septoria control on both upper leaves. In addition, Arizona at the T1.5 timing in an azole-only programme increased yield by over 1t/ha (where disease pressure was high). Arizona at T1.5 as part of a SDHI programme increased yield by 0.59t/ ha, said Mr Bailey.

“In the same comparison in another trial with Santiago, but with less septoria pressure, we saw an increase in yield from the T1.5 application, albeit 0.25t/ha” he added. “Folpet is an alternative multi-site product which has been shown to interfere less than chlorothalonil with a crop’s uptake of azoles and SDHis. “It can also be a good option at T2 with no interference with partner products,” he concluded. ■

Prescriptive spring herbicide approach takes out problematic weeds AICC agronomist Steve Cook of Hampshire Arable Systems.

Increasingly, for growers looking to clean up cereal crops as they approach the critical T1 timing, problematic broad-leaved weeds such as bur chervil, an aggressive member of the carrot family, are proving difficult to control using some standard herbicide programmes. So reports AICC agronomist Steve Cook of Hampshire Arable Systems who provides independent arable advice across, Hampshire, Wiltshire and Oxfordshire. He is adamant that a more prescriptively tailored approach is essential to get on top of this highly competitive weed and its cousin, the slightly

less common, but equally yieldrobbing and invasive wild carrot. In his clients’ rotations, which generally involve a run of three cereals and a break, the chance to hit these notoriously hardy weeds occurs at T0, combining an SU such as straight metsulfuronmethyl (Jubilee) with the first fungicide/PGR application at early stem extension. However, in recent years, the levels of control witnessed by using a single hit of that particular herbicide, have not been satisfactory enough and Mr Cook has been forced to rethink his approach. “We used to achieve perfectly good control with that method,” he says. “But the highly aggressive and competitive nature of both species, has meant that we’ve had to seriously beef up the efficacy.”

Combination Mr Cook is keen to point out that the SU chemistry is still very appropriate, but using a combination of active ingredients in products such as Harmony M SX (40g/kg metsulfuron-methyl

and 400g/kg thifensulfuronmethyl) and Ally Max SX (143g/ kg metsulfuron-methyl and 143g/ kg tribenuron-methyl) has made the difference between weed populations that have only been marginally suppressed and those where virtually 100 per cent control has been achieved, especially with optimum nozzle selection and good operator engagement. “These weeds need to be dealt with as early in the spring as possible,” he explains. “In the past where some of the more traditional residual herbicides such as IPU used to control them well, now gaps in the autumn programme mean these species have the chance to gain a foothold over winter, which makes it even more important to control them quickly and effectively, while they can still be targeted. “If they can’t be dealt with by GS31 then you’re looking at partial or even minimal control, which translates into yield loss, lower margins and of course ultimately more weed seed being returned to the bank,” says Mr Cook. “A single, well-timed, full dose of either Harmony M SX in wheat or spring barley, or Ally Max SX

in winter barley or wheat has given us the edge and growers are aware that this approach is essential if progress in reducing the populations is to be made.”

Spring loading As Mr Cook rarely has to treat crops for black-grass in the autumn, it means that his spring loading of SU chemistry can benefit from packing a full punch when it comes to bur chervil. “We aren’t really in a position where we have to apply much Atlantis or Lexus SX as part of our autumn programme,” he explains. “And because of that we’re able to ‘keep our powder dry’ until the spring, when rapid growth means accelerated uptake of the actives. “In the autumn it’s virtually impossible to tell which species is which, but by the spring it’s only slightly easier to differentiate. However, both are susceptible to that combination of chemistry and through our recent three years of trials work in Oxfordshire and Wiltshire, we’re confident that we’ve come up with a very workable solution. This has now been adopted as standard practice and is definitely producing results.” ■

• Reduced establishment cost • Better pest resistance • Better early establishment • Improved yield • Simple calibration

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