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1 The autumn gum moth Mnesampela privata (Guene´e) (Lepidoptera: Geometridae, Ennominae) is a native moth that can outbreak, resulting in significant defoliation of plantation eucalypts in southern Australia. 2 Laboratory trials tested M. privata larvae for their dose-response to the ecdysone agonist, Mimic 1 700 WP (a.i. 700 g/kg tebufenozide); ground and aerial field trials also tested its efficacy in eucalypt plantations. 3 The laboratory trials showed that there was no significant difference in mortality between larvae treated with 172 g Mimic 1 (120 g a.i)/ha and those sprayed with doses ranging from 86 to 3340 g Mimic 1 /ha. 4 Laboratory and field trials demonstrated that second instars were the most susceptible, with the most rapid response. However, second to fourth instars all reached 100% and fifth instars 90% mortality 3 weeks after aerial spraying at 120 g a.i./ha. 5 Aerial spraying an Eucalyptus globulus plantation with 120 g a.i. Mimic 1 at 20 L/ha caused 95% mortality of instars two to five, and 100% for instars two to four within 3 weeks after spraying. 6 Ground spraying to run-off with 120 g a.i. Mimic 1 /ha reduced defoliation of E. grandis from between 67% to 80% for unsprayed trees to 0% defoliation for sprayed trees. 7 The window for effective management of M. privata larvae is 3-5 weeks, during first to third instar development. 8 Replacement of broad-spectrum insecticides with the more target-specific Mimic 1 should increase the biodiversity of plantations and therefore would be more environmentally friendly.

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