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Arable

AGRONOMY UPDATE – NORTH

It may have meant a frustrating wheat harvest, but plenty of rain from mid-August has helped winter OSR off to just the start Sam Patchett was hoping for. Although we’ve plenty of wheat still to combine going into September, our spirits have steadily improved as the harvest has progressed. Not unexpectedly after such a miserably wet season well into April, our winter barleys and oilseed rapes were disappointing. However, winter wheats and spring barleys, with their later-maturity, have fared much better. At the same time, prices have pickedup encouragingly. Rapeseed at over £300/t and feed wheat around £120/t are currently well ahead of where we feared they might be both for this harvest and next. And nitrogen prices are a good £40/t down on this time last year. Better prices, an early start to the harvest and decent soil moisture levels mean our rape plantings are up this autumn. We drilled most crops in the last two weeks of August and they’ve come though evenly and

grown away strongly. Together with carefully targeted pelleting, this has been essential in dealing with some very threatening slug populations. Higher quality pasta or hybrid pellets are proving really valuable here, withstanding some pretty heavy downpours noticeably well. So they’ve more than justified their extra cost in reducing the need for re-applications. Providing conditions don’t turn bone dry, by the time you read this our vigorous OSR hybrids should be nicely beyond the main slug risk stage; especially so since most went in with seedbed N and without a pre-em. As well as avoiding any crop risk, we’ve made post-ems the focus of our early weed control so we can save an operation by combining the initial herbicide with the flea beetle spray we’ll almost certainly need. Thankfully – unlike some on the

Wolds – we haven’t had any beetle problems so far, but it’s early days yet and last season underlined the importance of protecting our crops from the larvae as much as the adults.

Weeds Where grass weeds are a significant problem we’ll be following this up with early carbetamide wherever we have sufficient moisture. It gives us much more spraying flexibility than clethodim and, while strong stem canker resistance in our hybrids means they’re unlikely to need early fungicide support, the same cannot be said for the most popular conventional varieties in the ground up here. All our winter barleys will be September-sown with a flufenacetbased pre-em, followed up with a pendimethalin-based post-em. Although Stow Longa trials show the crop to be markedly more competitive with grass weeds than wheat, they also emphasise the importance of pre-October drilling for the best performance.

There are plenty of aphids on volunteer barley in our OSR. So, with the only BYDV incidence at the Brotherton iFarm last season in a single undressed variety plot, Deter (clothianidin) treatment has been a priority. We’re also treating our barleys with Take-off to boost rooting, wherever possible. At five northern iFarms last season the dressing increased KWS Tower yields at a range of seed rates by up to 1t/ha and an average of nearly 0.6t/ha over Deter alone.

Later planting With the critical importance of later-drilling in black-grass control, where grass weeds are problematic we’re holding-off on wheat planting until mid-October. This should have a positive benefit for our insect and disease management too. More on which next month. Agrii agronomist, Sam Patchett works with growers across West and South Yorkshire as well as his own family’s farm (sam.patchett@agrii. co.uk). ■

AGRONOMY UPDATE – SOUTH WEST Barley yellow dwarf virus control is top of Cornwallbased Agrovista agronomist Martin Stuart’s to-do list this autumn. Last season’s barley yellow dwarf virus (BYDV) outbreak in the South West was the worst for at least eight years, says Martin. “It should serve as a wake-up call for all of us. I believe it was a major factor behind what was a pretty variable harvest. “Early-drilled crops generally performed worse than those drilled after mid-October. Although the dull June had an effect, BYDV was more prevalent in these crops.” The main BYDV vector in the South West is the bird cherry-oat aphid, elsewhere it’s the grain aphid. Early-drilled crops are exposed

BYDV was more prevalent in early drilled crops in the South West last season.

to autumn migration for longer and allow more time for aphids to reproduce in the crop. The pest thrived in the exceptionally mild winter, Martin explains. “After a few years of relatively low infection levels, when winters were just cold or rough enough to keep the pest in check, a level of complacency had perhaps crept in. “Aphids can soon reach damaging levels, resulting in high virus transmission that produces the classic yellow foci. In bad situations these can merge and whole fields can be affected.”

Green bridge The first step to combating BYDV is to remove any green bridge from ploughed-down grass or cereal volunteers, Martin advises. “Ensure fields have been left long enough for glyphosate to work.” Growers should avoid drilling early, he adds. “One week’s delay can halve the incidence of BYDV.” Seed treatments such as Deter (clothianidin) provide protection for six to eight weeks during the vulnerable seedling stages, which

is often enough in most areas. However, in the milder South West, a follow-up spray is usually required. “Crops should be closely monitored from six weeks after drilling, and treated as soon as aphids are seen,” Martin advises. Several pyrethroid treatments are available, but growers need to check labels. New straight cypermethrin products now carry an 18m drift reducing technology (DRT) watercourse buffer zone requirement as well as a 5m nontarget arthropod buffer zone. He recommends Colt (lambda cyhalothrin), which avoids the 18m buffer requirement. In addition, the product is a capsule suspension (CS) formulation which is relatively kind to the crop. “Emulsifiable concentrate (EC) formulations tend to be hotter. This is worth considering, especially when tank-mixing a herbicide and/ or treating a lush crop. If a salt-laden gale blows up, you can lose dewaxed plants in a big way.” Two sprays are usually enough. Subsequent aphid infestations can cause yield losses up to GS 31, though they tend to be less significant. Crops not treated with Deter should be sprayed once aphids are

seen, says Martin. “Be prepared to re-apply two to three weeks later, and again when a window appears if the autumn remains open and mild. “Last year some growers couldn’t follow up until early December. Nevertheless, despite this late timing, BYDV was noticeable by its absence in the spring compared with fields that weren’t re-treated at all. This indicates how long crops remain at risk while aphids are active.”

Barley pre-ems Pre-emergence herbicide applications are vital on winter barley given the lack of postemergence materials and shortage of spray days in the South West, says Martin. Main targets are annual meadow-grass and broad-leaved weeds. He recommends 800g/ha of pendimethalin, adding diflufenican and flufenacet as necessary. “Diflufenican will broaden the broad-leaved weed spectrum. Flufenacet will bring additional activity where meadow-grass pressure is high, or where other problem grass weeds are present.” Martin Stuart is an agronomist advising for Agrovista in Cornwall (Martin.Stuart@agrovista.co.uk) ■

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