Research by the Department of Primary Industries and Regional Development (DPIRD) has found barley loose smut is becoming less responsive to some fungicide seed treatments.
Research by the Department of Primary Industries and Regional Development (DPIRD) has found barley loose smut is becoming less responsive to some fungicide seed treatments.
DPIRD senior research scientist Andrea Hills said field trials this season had shown that a recently identified genetic mutation in some samples of barley loose smut was having an effect in the paddock.
The trials are part of co-invested Grains Research and Development Corporation (GRDC) and DPIRD barley projects in Western Australia.
Barley loose smut is a seed-borne disease that develops in the ear of the plant, replacing florets and grain with a dark brown mass of fungal spores.
Loose smut is most effectively controlled by applying a fungicide seed treatment before sowing which reduces seed transmission of disease and allows the ear to develop normally.
“Earlier this year, researchers at the Centre for Crop and Disease Management (CCDM) at Curtin University announced they had identified a genetic mutation in Australian isolates of barley loose smut that confers reduced sensitivity to the Group 7 SDHI (succinate dehydrogenase inhibitor) fungicides,” Ms Hills said.
“Three loose smut samples collected in WA during 2025 were tested by CCDM which all had high levels of the SDHI mutation.
“DPIRD field trials during 2026 at the Esperance Downs Research Station, Tenterden and South Stirlings showed that a range of popular SDHI seed dressings all had lower than expected levels of effectiveness against loose smut while Group 3 (Demethylase inhibitor or DMI) seed treatment effectiveness remained unchanged.”
DPIRD has also submitted samples of loose smut from across the grainbelt this season to CCDM to test how prevalent the fungicide resistance mutation is.
“Results from this analysis will be available soon and will enable us to understand the frequency and geographical distribution of this mutation,” Ms Hills said.
“Growers should be aware that if they are growing a susceptible variety such as Neo CL where treatment for loose smut is recommended every year, then the choice of seed dressing will be important since those containing only an SDHI are less likely to adequately prevent loose smut if the disease is resistant,” Ms Hills said.
“Instead, growers should look at using seed treatments that contain a different mode of action, such as a Group 3 (DMI) fungicide, particularly if they had poorer than expected efficacy from SDHI seed treatment in 2026.”
Other strategies to improve loose smut control such as cleaning and grading seed, prior to treatment, are recommended and treatment application is a critical step to minimise disease. Seed crops can be sprayed with a fungicide at head emergence which will reduce loose smut infection but not eliminate it.
Growers can have seed tested for levels of loose smut through DPIRD’s Diagnostics and Laboratory Services (DDLS) and consider replacing seed if more than five per cent is infected.
Barley variety ratings for susceptibility to loose smut will be available in the 2027 Western Australian Crop Variety Sowing Guide, which will be released soon.
