Winter wheat growers are being urged to be on the lookout for lurkingrust infections that could start to increase with warmer temperatures.
That follows sightings of foci of yellow rust infections in crops inEastern parts of the country, despite weather conditions having been less thanideal.
Independent agronomist Sara Harrison-Osborne, who operates in Essex andSouth Suffolk for Prime Agriculture, has seen yellow rust on varieties withHGCA Recommended List resistance ratings of six and four.
Although she points to Septoria tritici as the main disease this season,she believes rusts must not be overlooked. Last year it came in after a hotweekend, but we were expecting it. But this year you can find it despite thequite low temperatures that have not been ideal for rust. You can find yellowrust in five to six plant foci, she adds.
Syngenta field technical manager, Simon Roberts, confirms low-level rustsightings in counties such as Oxfordshire, Bedfordshire, Lincolnshire andthrough the Eastern counties.
High Septoria tritici levels can make it difficult to identify the smallrust pustules on older leaves, he says, but as temperatures rise, if leftunchecked, rust could start to flare up.
Septoria tritici is more prevalent, says Mr Roberts, so youve notgot the nice green leaves that make rust pustules so easy to spot.
Its not as bad as last year, but it is there. Its not been coldenough to kill the pustules, so rust has just been waiting for milderconditions.
As soon as it starts to warm up it will still start to build. Also,because rust cycles quicker than Septoria, you could see it develop morerapidly especially on susceptible varieties, he adds.
Stopping a rust build-up shouldnt be difficult, says Mr Roberts. Afterusing a T0 fungicide with rust activity, it will be important that fungicidesused at T1 and T2, in April and May, provide sufficient rust control tomaintain on-going protection where there is a threat, he adds. That isespecially so since brown rust threats can also increase later in the season astemperatures rise, he notes.
The SDHI fungicide Keystone offers ideal T1 and T2 protection in thesetypes of situations, says Mr Roberts, because, as well as protecting againstSeptoria, it also has long-lasting yellow and brown rust activity built in. Itcan also be mixed with chlorothalonil, such as Bravo, for extra Septoriacontrol which is useful given the significant Septoria threat were seeingthis season, he adds.
Prime Agricultures Sara Harrison-Osborne says her rust-susceptiblevarieties should have already received an early rust fungicide this season, todamp down the disease, prior to an SDHI + triazole + chlorothalonil mix likelybeing applied at T1 and T2.
Brown rust can be just as damaging as yellow rust, points out MsHarrison-Osborne. We have a range of varieties susceptible to either one orthe other, or both.