The efficacy of micro-injected imidacloprid and oxydemeton-methyl on red gum eucalyptus trees (Eucalyptus camaldulensis) infested with red gum lerp psyllid (Glycaspis Brimblecombei)

Abstract

A stand of red gum eucalyptus trees (Eucalyptus camaldulensis) heavily infested with red gum lerp psyllid (RGLP) (Glycaspis brimblecombei) was micro-injected at crown level with a single standard treatment of imidacloprid, oxydemeton-methyl, or a combination of both. Psyllid populations were monitored for 15 months following initial treatment. Significant mortality and reduced population levels of immature RGLP occured within 1 week following an application of all treatment materials. Oxydemeton-methyl was significantly effective, when compared to untreated trees, for approximately 2 months. Imidacloprid-treated trees showed statistically significant reduction of psyllid nymphs, compared to untreated trees, for approximately 8 months. The combination of both materials significantly reduced psyllid nymph populations for approximately 8 months. Many trees continued to show control up to 15 months with imidacloprid. However, nymph population variances among treatment trees were too high to statistically detect significant differences among treatment averages. The longer residual activity in some trees may indicate variability among individual trees sustaining levels of imidacloprid beyond 8 months.