Healthier pastures could hold the key to red-legged earth mite control
Kangaroo Island farmers dealing with red-legged earth mite are encouraged to look beyond reaching for a pesticide and consider whether pasture nutrition, plant stress and beneficial insects are part of the bigger picture.
With chemical, fuel and input costs continuing to rise, the Kangaroo Island Landscape Board is working with landholders to find more cost-effective ways to manage pest pressure while supporting pasture growth.
Red-legged earth mite is active across KI pastures this season, and many farmers are again weighing up whether to spray. But after several years of working with local farmers on pest and pasture management, the Board is encouraging landholders to ask a more useful question: why are some pastures being repeatedly attacked in the first place?
Kangaroo Island Landscape Board Agricultural Extension Officer Cassandra Douglas-Hill said repeated spraying could become an expensive cycle if underlying pasture health issues were not addressed.
“Farmers are spending money every year trying to spray their way out of red-legged earth mite, but in some cases we may only be treating the symptom,” Ms Douglas-Hill said.
“If the plant is nutritionally stressed, especially through deficiencies like boron, molybdenum or copper, it may be more vulnerable to pest pressure.
“The exciting thing is that correcting those issues can support pasture growth as well - so it is not just about pest control, it is about growing healthier feed. In many cases, once we know what is missing, it is not hard to start addressing it.”
Through the Board’s sustainable agriculture, soil extension and property management planning work, extension staff have been observing red-legged earth mite pressure on KI properties for about five years.
That work, supported by integrated pest management advice and recent sap testing with local agronomist Jenny Stanton, suggests mite pressure may be linked not only to pest numbers, but also to underlying plant stress and trace element deficiency.
Ms Douglas-Hill said spraying still had a place in some situations, but it should not be the automatic first response.
Broad-spectrum sprays can reduce mite numbers in the short term, but they can also knock out beneficial insects and predatory mites that help keep pest populations in check, especially in the following season.
One beneficial mite seen on Kangaroo Island is the Anystis mite. It is a fast-moving red predatory mite that can be confused with red-legged earth mite. These beneficial mites can help keep pest numbers in check.
Chemical resistance is also becoming a growing issue in parts of southern Australia, making routine chemical control less reliable over time. There is already confirmed resistance of RLEM to organophosphates and synthetic pyrethroids on the island.
Local agronomist and soil consultant Jenny Stanton said recent sap testing on KI properties had highlighted common deficiencies in boron, molybdenum and copper.
“It appears that clover with adequate boron levels is showing much less red-legged earth mite attack in the paddocks we have looked at,” Ms Stanton said.
“Where boron levels are satisfactory in the sap test, even when the plants were looking pale due to a manganese deficiency, we are not seeing the same mite pressure.
“I have been recommending boron and other trace minerals on KI where there are deficiencies seen in soil samples. "
The sap tests including the ones done by Jenny are now confirming where deficiencies are in the plant, not just soil.
The Board is encouraging farmers to use monitoring, protect beneficial insects, good grazing management, consider plant nutrition and seek advice before making spray decisions.
“If a farmer can avoid a spray, protect beneficial insects, correct a deficiency and grow more healthier pasture, that is a much better outcome than simply reacting to the pest every year,” Ms Douglas-Hill said.
“This is not about never spraying. It is about not spraying our way into a worse problem.
“If we keep removing beneficial insects and ignoring plant nutrition, we should not be surprised when the pest keeps coming back with increasing pressure.”
The Kangaroo Island Landscape Board is not recommending a one-size-fits-all approach. Rates, products and timing depend on the paddock, pasture species, test results, grazing pressure, existing pest pressure and seasonal conditions.
Landholders wanting advice on red-legged earth mite, plant health, sap testing or property management planning can contact the Kangaroo Island Landscape Board’s Sustainable Agriculture team, contact:
Cassandra Douglas-Hill
Agricultural Extension Officer
Kangaroo Island Landscape Board
M: 0487 470 082
E: cassandra.douglas-hill@sa.gov.au
