Growers should not be alarmed by active yellow rustin early sown wheat advises a leading cereal pathologist.
Themild autumn, coupled with a large spore load from this summer, has resulted inearly symptoms of the disease, even on resistant varieties. However, Dr SarahHoldgate, project manager of the HGCA-funded UK Cereal Pathogen VirulenceSurvey (UKCPVS), says that growers can expect to see yellow rust at this stageon some varieties rated at 8 or 9 on the HGCA Recommended List.
Eventhe most resistant varieties can sometimes have yellow rust infection in theautumn, but adult plant resistance means that the plant will outgrow thedisease at a later growth stage, says Dr Holdgate. UKCPVS research, onsamples of yellow rust collected in 2013, has shown that some varieties, suchas KWS Cashel, Icon and Zulu, have a degree of susceptibility as seedlings toone or more of the isolates tested. All went on to have little or no diseasewhen it came to the crucial adult plant stages.
DrHoldgate does warn growers however that on susceptible varieties yellow rustseen now could carry through to next spring. “Very cold winter conditionscan slow the disease but unless the infected leaf is actually killed, thefungus will survive through to the spring.”
BillClark, Commercial Technical Director at NIAB TAG confirms this and says: Wevehad early reports of yellow rust appearing in crops, similar to 2013. This isto be expected given the widespread rust in 2014, which was predominantly theWarrior race, and the very mild conditions in September and October.
Mr Clark advises early infections such as this can be difficult to control ifthey become established on susceptible varieties during the winter months. Onceplants are infected they will usually carry infection through the winter,producing an early spring epidemic. However, spraying against yellowrust in the autumn is rarely needed except in exceptional circumstances normally the rust can be tackled in the early spring, he says.
Aspart of the monitoring programme Dr Holdgate is asking growers with substantialamounts of yellow rust in their crops to send samples of the infected leaves tothe UKCPVSat NIAB Cambridge.
“Inthe past weve had an excellent response from the arable community with samplescoming in as early as 18th November in 2013. Results from the2013/14 tests will be published in early 2015, with a summary at our annualStakeholders Meeting on 5th March, finishes Dr Holdgate.