Field screening for genetic-based susceptibility to mammalian browsing

Browsing by mammalian herbivores is a major problem in plantation forestry. Seedlings are most vulnerable to browsing during establishment, making protection crucial during this period. Aside from reducing herbivore numbers, browsing can be controlled through the application of tree guards or chemical repellents. These methods are generally short-term options. A promising, potentially longer-term method of reducing browsing damage on plantations is to plant individuals with enhanced natural browse resistance. This requires the development of a rapid, cost-effective means of identifying germplasm with enhanced resistance. Here we present such a screening methodology. We planted Eucalyptus globulus seedlings from 22 different seedlots in randomised blocks along edge rows of six operational plantations. Seedlings were monitored for mammal browsing damage and growth for 2 years. Natural variation between E. globulus seedlots resulted in significant variation in the extent to which they were browsed. Differential browsing was evident just 10 weeks after planting, and caused a significant effect on tree growth after 2 years. Differential browsing was thought to be due to variation in levels of plant secondary metabolites (PSMs). The identification and selective planting of high PSM seedlots in high risk areas could be an effective management tool to reduce browsing in plantation forestry.