Higher azole rates protect SDHI fungicides

Maintaining higher rates of azole fungicide treatments will help protect vital SDHI chemistry without increasing resistance risk, according to new research.
 

Work carried out by Rothamsted Research has shown the number of azole applications drives resistance, rather than dose rates.

 

Fiona Burnett of Scotland's Rural College (SRUC), who was involved in the project and also chairs the UK Fungicide Resistance Action Group, says it comes as a welcome boost to cereal growers and will help maintain azole and SDHI performance in the years to come.
 

“It’s a win-win situation, because we can protect SDHI chemistry without making it worse for the azoles, which was previously the worry when using higher azole rates.”
 

The new findings come ahead of what is set to be a busy period for farmers, with cereals accelerating through the growth stages and becoming increasingly susceptible to disease.
 

T1 and T2 remain at the core treatment timings, with robust azole rates being advised to achieve effective control and help protect any SDHI partners.

 

Additional timings at T1.5 and T4 should be avoided where possible, as they will increase selection for resistant strains of septoria.
 

Growers are also urged to use lower rates of SDHIs where they can still get effective control of diseases such as septoria. This comes following growing concerns over resistance being amplified by using higher dose rates of the chemical group.
 

Throughout septoria control programmes, it will be important to use a range of modes of action and maximise the use of multi-site actives such as chlorothalonil that have a low resistance risk, to protect azoles and SDHIs and prolong their useful lifetimes.
 

Strobilurins will provide a useful alternative where rusts are problem, while multi-site inhibitors offer protection for septoria at T0.
 

The research was done as part of a Defra Arable LINK project HGCA project and carried out by Rothamsted Research with additional work, funding and support from HGCA, ADAS, BASF, Bayer, DuPont, SRUC, Syngenta and Velcourt.