Hutchinsons is warning that early developing winter wheat crops may require a late ear spray this season due to late attacks of rust and sooty moulds. Yellow rust has been found in varieties with high resistance to the disease, indicating a new race, while brown rust may occur in warm conditions and control of sooty mould is particularly important in milling wheat.
“Although most crops are having their T3 this week many crops of winter wheat are well ahead of their normal growth stage this season meaning that, if there is sufficient moisture, there may be an extended period after their earlier T3 fungicide application before harvest,” said Dr David Ellerton, technical director at Hutchinsons.
He added that weather conditions may allow late season diseases to develop, particularly if wet weather continues after the T3 ear spray. “Septoria may also build if there is significant rainfall. In addition, yellow rust is widely reported including varieties such as KWS Extase which until now have been highly resistant to the disease with a rating of 8.”
Should the weather turn warm, this could also cause brown rust to develop in varieties such as Crusoe. “However, once flowering is complete only very limited, if any, control of Fusarium and Microdochium may be achieved.
“Where sooty moulds are developing an application of a strobilurin such as fluoxastrobin or azoxystrobin should be made as soon as possible after the disease is seen or as a protectant on milling varieties if wet weather is forecast.
“Strobilurins will also help the crop to retain green leaf area as well as withstanding stress conditions although it should be remembered that only two strobilurins are allowed per crop. For yellow or brown rust, products containing tebuconazole or metconazole should be applied which will give rapid knockdown while strobilurins will give extra persistence,” he said.
“Prothioconazole will help on yellow rust and mildew and may give extra persistence against the late development of Septoria tritici.
“As for multi sites, folpet can be used only up to GS 59, sulphur up to GS 61 and mancozeb up to GS 65. Trials work has also shown a benefit of adding Wetcit into ear sprays for disease reduction and it may also help reduce aphids, preferably in combination with an insecticide where aphid numbers are significant.”
Dr Ellerton concluded that growers should check the latest time of application for their chosen products.
