Arable
Tackling the increased take-all risk in wheat How can growers minimise the impact of the soil-borne pathogen take-all, as visible symptoms in current crops hint at increased risk for consecutive cereals drilled this autumn? The level of take-all inoculum has been high this year, with symptoms starting to show in crops after a dry spell leading into the harvest period. This is leading to a warning about the potential for primary infection this autumn in second and third wheats, and growers are advised to invest in a seed treatment to protect yield.
Ideal conditions Take-all is a soil-borne fungus that effects the roots of second and consecutive cereal crops, but it takes a certain set of conditions over the growing period to be met to see the most striking symptoms. Over the past 12 months, these parameters have been met, with a mild and wet winter allowing the disease to get a foothold in crops. A relatively dry spring followed, and, in many years, this would be enough to reduce disease progression, but capped soils have helped to retain moisture in the root zone on more bodied soils. In turn, this has led to significant secondary spread of the disease from roots infected in the autumn to new roots produced in the spring, damaging their ability to supply water and nutrients to above ground biomass. Now, with hot and dry weather prevailing, distinct patches of affected plants are visible in second
and third cereals, with stunted plants and ‘white heads’, where ears are empty of any grain – the tell-tale sign of take-all damage.
Nutrient struggles One agronomist that has seen takeall symptoms in commercial crops is Syed Shah, southern regional agronomist with NIAB, and he expects the disease to impact on final yields. “It’s been worse on lighter, drier soils and where early nitrogen wasn’t applied, with the take-all effect on rooting meaning that plants struggle to get the nutrients they need,” Mr Shah explains. In his area across Sussex, ProCam’s crop production manager Mike Thornton (pictured) hasn’t seen significant take-all symptoms himself, but ProCam colleagues have shared images of its impact on wheat crops elsewhere in the country. He says it has been worse in wetter parts, where rooting may have been lazy or compromised by compaction. “Then, when the dry time arrived from April onwards and the water table dropped, problems started to become evident. “When plants aren’t taking up
nitrogen, they drop tillers and the remaining ones produce poor grains and we’ll start see its true impact when the combines make a start,” says Mr Thornton.
Rotational options Mr Thornton reckons that after some rotational disruption over recent seasons, growers across his area are increasing their oilseed rape area to break long runs of cereal crops. However, Dr Shah says some of his clients are considering planting more second or third wheat crops given the relatively strong wheat price and the crop offering relatively consistent results. Much will depend on grassweed control in the previous wheat crop, but with new chemistry in Luximo (cynmethalin) giving an edge over flufenacet against blackgrass, it may offer further encouragement when considering consecutive cereals. “Last year, second wheats outyielded first wheats in many cases due to the crop being drilled later and suffering less disease. “Even if you achieve 7.5t/ha with a second or third wheat, it will still pay for itself given the strong grain price,” he explains. In these situations, crops will
be vulnerable to take-all and he says Latitude (silthiofam) and phosphite-based seed treatment to encourage rooting are two things he recommends as a matter of course in most situations. “There is nothing you can do about take-all later in the season, so why would you compromise the crop by not using Latitude?” says Dr Shah. Mr Thornton agrees and says although the right variety choice can help a crop withstand the effects of take-all and is an important piece of an integrated control strategy, the genetics still need support. Latitude will reduce primary infection that can spread and create the patchy symptoms that characterise the disease. “If you opt for a second or third wheat, I will say use Latitude. I can’t see a reason why you wouldn’t because it’s a disease that can halve yield. “If you are going to grow and invest in these crops, you should do it properly and get things right from the start. There is no going back afterwards,” he adds.
Nutrition key Dr Shah says higher seed rates, drilling into a good quality seedbed and consolidating after drilling is key in second or third wheats, along with continued over…
12 www.farmersguide.co.uk August 2022
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