FARMERS who suspect red leaf syndrome in their subterranean clover are reminded free testing is available again this season.
The Department of Primary Industries and Regional Development (DPIRD) and The University of Western Australia (UWA) are keen to test plants with symptoms as part of broader work to better understand this syndrome, which can severely stunt pasture growth.
Department research officer Paul Sanford and UWA researcher Kevin Foster are co-leading the work.
Sub clover red leaf syndrome symptoms include red leaves, stunted plants and even premature plant death.
The syndrome has occurred in the central and southern agricultural areas of WA for many years, however surveillance was initiated in 2017 after severe losses occurred for the first time in some areas.
Laboratory testing by the department plus field and glasshouse trials have identified the soybean dwarf virus (SbDV) as the probable cause, with other factors, such as environmental stress and root disease, likely to contribute to the severity of the syndrome.
Loss of sub clover production is greatest when the plants are infected by the virus in autumn or early winter.
"Soybean dwarf virus is not a seed-borne virus but is spread by aphids," Mr Sanford said.
"If we control the aphids there is a good chance we can manage the syndrome.
"Autumn control options to consider include spraying for aphids using an anti-feeding insecticide at two and six weeks after sub clover seedlings emerge.
"This group of insecticides prevents aphids feeding and therefore reduces the risk of virus infection."
Oats can also be sown as a barrier around pasture paddocks to disperse aphids and slow early spread into pasture from outside sources.
Mr Sanford said researchers were yet to find aphids in the Albany region this season and suspected the risk of an outbreak this autumn was low, but reminded farmers with symptoms in their sub clover that free testing was available.
"Growers who provide samples are provided with the test results and management advice," he said.
Meat and Livestock Australia (MLA) and Australian Wool Innovation continue to host an online producer survey, which enables producers to report incidents and assists the livestock funding bodies to determine the extent of the problem.
To contribute to the survey go to the MLA website.
To arrange free testing, contact Paul Sanford on paul.sanford@dpird.wa.gov.au or Kevin Foster at kevin.foster@uwa.edu.au
