Canopy management of macadamia nut trees and understory plant diversification to reduce macadamia felted coccid (Eriococcus ironsidei) populations

Preliminary observations suggest that macadamia nut tree canopy density plays an important role in E. ironsidei colonization and subsequent build-up of high population density. Combining techniques of canopy thinning with the provision of nectar and pollen plant sources for beneficial insects in the understory may result in improved E. ironsidei suppression. We investigate the role of canopy modification and understory habitat in enhancing natural enemy effectiveness to reduce E. ironsidei populations. Plots with pruned trees plus wildflower beds resulted in 47% less E. ironsidei than the control plots, and the pruned-only plots had 15% less E. ironsidei numbers compared to the control plots. Greater abundance of natural enemies was found in the treated plots than in the control plots. Predatory beetles were 64 % more abundant in the pruned trees plus wildflower beds than in the control plots, and in the pruned-only plots there were 52% more predatory beetles than in the control plots. Encarsia lounsburyi, a parasitic wasp that parasitizes, E. ironsidei was 20% more abundant in the pruned-only plots than in the pruned plus wildflower beds and control plots. Our results provide evidence that pruned macadamia trees and understory plant species diversification support natural enemy populations, and may provide enhancement of biological control of E. ironsidei in macadamia nut orchards.