Resistance management field trials underway for RLEM

With resistance issues on the rise in the redlegged earth mite (RLEM), cesar is collaborating with the University of Melbourne, CSIRO and WA DPIRD to find better management options for controlling populations that have acquired resistance to conventional chemistries in Australia.

Field exclusion plots were constructed in early 2017 to isolate resistant populations of RLEM and in turn, measure their response to a variety of management strategies. Resistance was manipulated in each plot so that mites were only moderately resistant to pyrethroids and organophosphates. The plots were then exposed to a variety of treatments including pyrethroids, organophosphates, and novel chemistries not yet registered.

The preliminary showed strong differences between treatments. Pyrethroids rapidly lost effectiveness as the populations quickly shifted to 100% resistant within the season. The story for organophosphates is more complicated with some actives, retaining a level of control, while others, offered little control in resistant populations. The long-term viability of organophosphates as a control method in resistant populations is unlikely and highlights the shortage of control options available to growers who are frequently encouraged to rotate chemical groups.

The good news is that treatments involving a novel chemistry were highly effective, suggesting no cross-resistance with this chemical group. These results will encourage future registrations of products. 

These field trials will continue in 2018 and preliminary results will be confirmed with ongoing studies.

Dr. James Maino, cesar

jmaino@cesaraustralia.com

+61 3 9349 4723