Spring control of redlegged earth mites in pastures using Timerite®
- Boyup Brook
Ben Creek (AGRIvise) has reported finding redlegged earth mites (RLEM) in pastures, particularly pasture with lots of capeweed, from Boyup Brook to Manjimup. Ben is concerned that forecasted frost events for this area may cause RLEM problems.
Spring has sprung and growers and consultants are reminded to monitor for RLEM in pastures and to find out their specific Timerite® spring spray date if spraying is necessary. Examples of Timerite® dates; Northam 11th September, Dandaragan 16th September, Tambellup 20th September, and Mount Barker 5th October.
The timing of the sprays is based on a short window of the season when RLEM have stopped laying winter eggs (eggs that must hatch this season) and before they start laying diapause eggs (over-summering eggs able to survive until next autumn).
Controlling mites at this time means that the whole population can be reduced, leaving few mites to carry-over to the following autumn.
Growers who have not already obtained their spray date that is specific to their locality can do so (free of charge) from the Australian Wool Innovation (AWI) Limited Helpline on 1800 070 099 or you can type the latitude and longitude of your property into the AWI TIMERITE® page to obtain your spray date and other useful information.
Studies by CSIRO have shown that spraying up to two weeks earlier or on the optimum spray date provides effective control of RLEM, however if spraying is delayed by two weeks after the optimum date the carry-over RLEM population into next autumn is much higher.
Farmers intending to spray paddocks should make the most of suitable weather conditions to go early or on time, rather than later than the predicted Timerite® date.
Growers are advised to spray only if they need to and to rotate chemical groups to stop resistance developing in RLEM. Repeated use of synthetic pyrethroid insecticides or organophosphates insecticides such as omethoate and chlorpyrifos provides strong selection pressure for RLEM to develop resistance. For more information refer to GRDC’s RLEM Resistance Management Strategy, and the IPM Guidelines for Grains website.
Growers who find RLEM that survive registered rates of insecticide treatments are encouraged to arrange for resistance testing to be conducted by contacting DPIRD entomologist Svetlana Micic, Albany on +61 (0)8 9892 8591 or 0427 772 051. The free-of-charge service, made possible with investment by the Grains Research and Development Corporation (GRDC), is led by The University of Melbourne, in collaboration with DPIRD, cesar, and CSIRO.
Grazing reduces mite carryover in pastures
The level of grazing and quantity of pasture feed on offer (FOO) is directly related to the numbers of RLEM. Department grazing trials have shown that pasture grazed to 1.4t/ha FOO during spring will have low levels of mites, equivalent to numbers after spraying pastures with high FOO level.
Spraying of pastures in spring will have little or no benefit where pasture FOO levels are kept low by grazing. Insecticides applied to control RLEM in spring pastures or legume break crops with FOO levels greater than 3t/ha will reduce their numbers and provide benefits by allowing increased spring growth and seed set and a much reduced potential for RLEM carry-over into next autumn.
However, increased production benefits can largely be wasted unless the increased feed is utilised by strategic grazing management or fodder conservation. It is recommended that farmers should not spray all pasture paddocks but rather select paddocks for spring spraying based on FOO levels, future grazing feed management, level of required seed production and intended paddock use next autumn.
For more information on RLEM refer to the department’s Diagnosing redlegged earth mite page.
For more information contact Dustin Severtson, Development Officer, Northam on +61 (0)8 9690 2160 or Svetlana Micic, Research Officer, Albany on +61 (0)8 9892 8591 or Alan Lord, Technical Officer, South Perth on +61 (0)8 9368 3758.
Article author(s): Cindy Webster (DPIRD Narrogin), Dusty Severtson (DPIRD Northam) and Alan Lord (DPIRD South Perth).