Mitigating take-all risk in second and third wheats

06.07.2017

With take-all described as an endemic disease to UK soils, particularly affecting second and subsequent wheats, growers are at risk of yield losses of up to 4 t/ha if the disease is not kept in check.

Agrii’s Seed Technical Manager, David Leaper, takes a look at the risk factors and how growers can manage this potentially devastating disease through an integrated approach of both cultural and chemical methods.

The soil borne disease

“The take-all pathogen builds up in first wheats but seldom affects yields. Where a second wheat is drilled, the emerging roots come into contact with the debris of the previous crop and transfer the pathogen to the new crop,” explains Mr Leaper.

“The pathogen then forms necrotic lesions on the roots which compromises the plants ability to extract water and nutrition from the soil, in order to sustain itself. As a result of this, we can start to see patchiness in the crop and whiteheads in severely affected crops. However, in most instances we see no visible effects but an underlying erosion of wheat yields is occurring.”

Considering the potential yield losses, growers need to look out for the crop risk factors, such as weather and soil conditions, in order to mitigate the effects of the disease.

“This year we’ve seen a mild winter followed by a cool and very dry spring, which means that good rooting has been very important.

“Root and tiller survival in second wheats, especially on lighter land, has been compromised this year but the effects on final yield now very much depends on the weather conditions during grain fill,” he adds.

“Soil types can also have a great baring on how much risk your crops are exposed to.  Medium to heavy soils can incur yield losses of up to 20 percent and light sandy soils can be far higher. As second wheats generally yield up to 1.5 t/ha less than first wheats, understanding these variables is crucial to ascertain the risk level.”

Managing take-all

“When managing take-all risk, growers need to consider both cultural controls, such as drilling date and variety choice, and chemical controls in the form of a specialist seed treatment.

“In the early 2000s we saw a big shift towards early drilling of both first and second wheat fuelled by the need to get large crop areas established early. This increased the risk of severe talk-all significantly.

“However, in the last three years there has been a shift back to later drilling in order to manage blackgrass.

This has reduced the pressure of severe take-all, but it is still an underlying problem wherever second wheats are grown, which growers must be mindful of.

“In the past, growers were using a seed treatment such as Latitude, to give them flexibility. Allowing crops to establish early and to mitigate the effects of take-all. The reality is that optimum output is always best when the crop is drilled in mid-October.  In this case, Latitude is used to maximise second wheat output and is consistent with where drilling dates are now sitting.”

Mr Leaper also explains that variety choice is an extremely important tool, especially when looking at second wheats, as some varieties are more robust than others, when it comes to take-all.

“Graham for example, is an extremely profitable first wheat with good disease resistance and good yield, but we’ve seen it struggle in a second wheat slot. However, varieties such as KWS Zyatt, Evolution, Relay, Dickens and Skyfall are very natural second wheat options.

“In some circumstances growers do not have the luxury of flexibility in their variety choice, usually due to storage options. In this situation, we’d advise they choose the same variety as their first wheat, that they know works well on their land, but insure this with a seed treatment.

“Ideally, you want to cover all bases, and employ an integrated approach to disease control in order to mitigate the effects of take-all and ultimately protect yields,” says Mr Leaper.

Seed treatment options

This year, Latitude (silthiofam) is the only specialist seed treatment approved for the control of take-all. Chris Charnock, Certis’ Arable Product Manager, explains how growers can use it to ensure their crops have protection, from day one, against the soil borne disease.

“Studies have shown that seed treatments offer a significant yield response when used on second wheats.

“Latitude has unique activity against take-all. It works by creating a zone of protection around the newly emerging root systems of the crop, therefore stopping the take-all inoculum from coming into contact with the fragile young roots.

“The silthiofam-based treatment is proven to reduce the level of take-all in second wheats by half, with the potential of generating an average yield response of up to 0.55 t/ha,” he adds.

“When it comes to take-all management and mitigating its effects, growers must first observe cultural controls. But, for added protection and an insurance policy for yields and profits, the inclusion of a seed treatment is a robust and cost-effective option,” concludes Mr Charnock.