Cold weather fails to halt rust infection

Despite the cold winter – which was thought may have killed off infections – early reports of yellow rust are starting to emerge from several parts of the country.

So far, these include Lincolnshire and various parts of the Midlands, but others may be affected, says Syngenta disease specialist Rod Burke.

“Although we don’t yet know how these early infections will develop, it’s important growers factor them into their thinking for early season disease control, in order that crops aren’t left exposed. Many people may have thought the cold winter would have killed off rust problems.”

Plant pathologist Bill Clark, director of Broom’s Barn research centre, has also picked up early rust reports. Although it can be difficult distinguishing between yellow and brown rust at this time of the season disease is certainly present, so it’s not alarmist to consider rust along with septoria tritici at the April T1 spray timing, he says.

In the Midlands, TAG agronomist Chris Page has found yellow rust on the variety Robigus in Northamptonshire.

“It’s not surprising given the conditions and the variety.

Although it’s been very cold and dry, the recent milder weather has helped the disease develop. Moisture from overnight dews or rain will continue to provide opti-mum conditions for development.”

Getting the T1 timing right will be key on backward crops, says Mr Clarke.

As plants are likely to produce fewer leaves per stem, leaf three could emerge earlier than expected – meaning growers will need to be extra vigilant with crop inspections.

Dissect plant

“People who normally look for second node may well find that leaf three comes out at first node. The only way is to dissect the plant. But if you’re not bothered my inclination would be to go slightly earlier,” he says.

Mr Burke says the mobility of certain fungicide ingredients will give a little more leeway if application is made slightly earlier. 

If growers have been considering a Proline (prothioconazole) treatment at T1, they can simply tank mix Cherokee (chlorothalonil+

cyproconazole+propiconazole) with it to boost rust activity and provide extra septoria tritici activity, he says.