There is wide Research and Managment gap of serious insect pests on various indigenous and or invasive tree species including eucalyptus in the country
I think you can, maybe if it's just for the thesis the research scope is about identification and distribution. Then for the dissertation, it's better to discuss the typical pests on the tree. Maybe anatomically or genetically
I think it can be a PhD dissertation. You would have to develop an achievable research scope. Discuss the pest in relation to a specific Eucalyptus spp or you could discuss base on all the Eucalyptus spp identified in the region.