27 May 1998
Strobilurins and fusarium
I HAVE heard recently that the strobilurin fungicides can actually
increase the incidence of fusarium. Is this correct?
Dr Keith Dawson, CSC Cropcare, Perth
THIS query has probably arisen because of trials carried out in France by ITCF which introduced populations of Fusarium culmorum – the dominant fusarium species in France – into trial plots and failed to get good control with strobilurins.
In the north of the UK we are more concerned about controlling Fusarium nivale, which is the more common species. We only have anecdotal evidence regarding the effect of kresoxim-methyl on fusarium after looking at a couple of sites – one in Aberdeen and another in the Borders – where growers had applied Ensign (kresoxim-methyl + fenpropimorph) at wheat flag leaf to single strips in otherwise conventionally-treated fields.
The Aberdeenshire field was going into spring barley, so the stubble was left. It was very evident that the strip treated with the strobilurin had a much cleaner stubble, while the rest of the field was visually dirty with fusarium.
Winter barley was drilled after winter wheat in the Borders, and was again visually seen to be much stronger come December on the strip which had been treated with the strobilurin in the previous crop. Levels of fusarium were again much higher in the untreated part of the field.
I wouldnt support the view that strobilurins increase fusarium. It may be a similar situation to obtaining good control of eyespot, only to highlight the presence of sharp eyespot which had previously been masked by the more dominant disease.