Understanding, conserving and effectively managing forests is an important undertaking for managing and maintaining biodiversity, indeed globally around 65% of terrestrial taxa are supported by these ecosystems. In Australia, forest conservation is particularly important in terms of eucalypt-dominated forest, with 79% of forests in Australia dominated by eucalypts. However, the rapid and premature decline of leaf biomass in eucalypt trees, a process known collectively as 'dieback', has been observed in many eucalypt stands nationally, with the factors and processes determining mortality remaining poorly understood. Bell miner associated dieback is a particular type of dieback that has been associated with the presence of, and tri-trophic interactions among bell miners, 'Manorina melanophrys', a native, despotic honeyeater, an introduced plant lantana, 'Lantana camara', and arbivorous insects such as psyllids. Together, these three factors have been suggested to cause dieback throughout southeast Australian forests where these groups co-occur. To gain a greater understanding of this phenomenon, this thesis examines the impact of foliar herbicide application on subsequent lantana health, bell miner density and habitat selection, soil chemistry and overall canopy health.