Growers and consultants are urged to check for lucerne flea and mites
An agronomist reports finding redlegged earth mites (RLEM) causing low levels of feeding damage to pastures around Capel and Boyanup. The pastures were dry sown and germinated following the first rain for the season. As a result, the pastures got a head start on the mites and were well established before the RLEM emerged following the more recent cooler wet weather.
The substantial rainfall and low temperatures experienced recently across the state is expected to have triggered lucerne flea and RLEM hatchings.
Due to the delayed start to the season there are some canola and cereal crops that are just emerging, coinciding with lucerne flea and mite hatchings, and they will be susceptible to feeding damage.
The lucerne flea is a Collembolan or 'springtail'. Adult lucerne flea are approximately 3mm in size and green-yellow in colour. It attacks a range of crops and pastures, causing characteristic ‘windowing’ of leaves. They work up the plants from ground level, eating tissue from the underside of the foliage. Loamy and clay soils are known to support higher populations of lucerne flea than soils with low clay/silt content because the fine clay is required for reproduction.
RLEM are a sap-sucking pest of crops and pastures. Adults are 1mm long with a black body and eight red-orange legs. RLEM have a cold temperature requirement (generally seven days below 20°C average daytime temperatures) before the eggs are triggered to hatch. RLEMs do co-exist with blue oat mites so make sure you correctly identify what mites you are finding. Blue oat mites look similar but have a red dot on their back.
For earth mites, correct identification is critical for effective control, as different species can vary in their susceptibility to certain insecticide groups, either naturally or through insecticide resistance. You can report and confirm the identity of mites by using the PestFax Reporter app.
Management of lucerne flea and RLEM
Insecticides will not kill RLEM eggs so it should not be assumed that a pre-sowing insecticide application has killed all mites that could be present during crop germination.
Lucerne flea have a high natural tolerance to synthetic pyrethroids so avoid insecticides from this group.
For more insecticide information refer to DPIRD’s 2018 Autumn/Winter Insecticide Guide.
RLEM insecticide resistance and 2018 resistance surveys
RLEM surveys for resistance will again be undertaken in 2018. Western Australia is now not the only state to have RLEM that are resistant. Three populations of RLEM have been found in South Australia which are resistant to commonly applied insecticides including synthetic pyrethroids (SPs) (Group 2A) and the organophosphates (Group 1B) omethoate.
In WA, we have detected RLEM populations with high levels of resistance to SPs, including bifenthrin and alpha-cypermethrin and the organophosphates (Group 1B) omethoate and chlorpyrifos. Detections of resistance are becoming more common across the WA grainbelt.
Growers and consultants are urged to apply integrated pest management (IPM) strategies when managing RLEM. These strategies include; identifying mites, rotating different chemical groups and reserving co-formulations or chemical mixtures only for situations where damaging levels of RLEM and other insect pests are present. For more IPM information see DPIRD’s Prevent redlegged earth mite resistance page.
If you are noticing that RLEM are surviving registered rates of insecticide treatments or are causing damage to germinating crops consider contact Alan Lord or Svetlana Micic to arrange for resistance testing.
To check out previous mite activity this season refer to the 2018 PestFax Issue 5 article Insect pest activity this week.
For more information about diagnosing and managing lucerne flea and different mites refer to the departments;
- Diagnosing lucerne flea
- Diagnosing bryobia mite
- Diagnosing balaustium mite
- Diagnosing blue oat mite
- Diagnosing redlegged earth mite pages.
For more insect information contact Svetlana Micic, Research Officer, Albany on +61 (0)8 9892 8591 or Dustin Severtson, Development Officer, Northam on +61 (0)8 9690 2160 or Alan Lord, Technical Officer, South Perth on +61 (0)8 9368 3758.