Don’t overlook yellow rust risk

If you’re planning to grow wheat varieties susceptible to yellow rust this autumn, then a seed treatment could be a worthwhile investment, according to experts.

Last season was not a big yellow rust year, but the potential is there for inoculum to increase over the winter, says ADAS Boxworth’s Bill Clark.

“The risk is only low to moderate in terms of the amount of inoculum around at the moment, but a mild autumn and winter means the risk could be high going into next spring.”

The situation is compounded by the relatively large area of susceptible varieties likely to be sown this autumn, he notes.

“Last year considerably greater amounts of yellow rust were found on Robigus,” says Dalgety’s Mike Jeffes. “The chances of a green bridge forming from volunteers being reinfected and acting as a source of inoculum are much higher than in the past.”

Kent-based Hutchinson’s agronomist, James Short, adds: “A hard winter generally kills most of the inoculum, but if your crop’s had it [yellow rust] this year, then it’s probably worth considering a seed treatment.”

Growers should identify the weaknesses of every variety before drilling and manage the crop accordingly, he says. In some cases, it will be worth growing a number of varieties with different strengths and weaknesses.

In the south east particularly, brown rust could also be a threat, especially in susceptible varieties such as Claire, he notes.

Control options

Mr Clark says that many seed treatments offer good foliar disease control, particularly of yellow rust, which is relatively easy to control.

“They’re largely a management tool that will give you a bit of leeway and insurance in the spring if spraying is held up by the weather, or you’re in a particularly high risk area, such as East Anglia.”

The main products include Epona (fluquinconazole + prochloraz), Baytan (fuberidazole + triadimenol) and Jockey (fluquinconazole + prochloraz) and all give good levels of control, he notes. “There’s little to choose between them.”

Epona is likely to cost about two-thirds the price of full-rate Jockey, so may be more appropriate for less productive second wheat Robigus, says Mr Jeffes.

It may be worth reducing seed rates by 30-50 seeds/sq m, compared with the rates normally used for other varieties, he adds.

This reduces the risk of crops becoming over-thick and more susceptible to yellow rust or mildew. The saving (3.50-6/ha) should cover the cost of treating seed, he says.

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