Non-lethal strategies to reduce browse damage in eucalypt plantations

Browsing by mammalian herbivores is a major problem in plantation forestry worldwide. This has traditionally been controlled through a reduction in herbivore numbers achieved by lethal means, namely shooting and poisoning. In recent years, however, there has been increasing social and political pressure to reduce reliance on such lethal controls, and consequently research into non-lethal controls is becoming increasingly important. In order for non-lethal methods to be efficiently incorporated into management, however, we must first identify those that are most effective under operational conditions. Different methods are rarely tested concurrently, and many have only been proven effective with captive animals or in small scale field trials. This study therefore sought to consolidate past research by combining non-lethal methods, which were known to significantly reduce browsing damage, into a single trial to enable their relative effectiveness to be compared under operational conditions.Eucalypt seedlings with combinations of browsing resistance, nursery fertilizer, chemical repellent (Sen-Tree) and tree guard treatments were planted in replicated blocks spread around the perimeter of eight operational plantations across Tasmania, Australia. Seedlings were monitored regularly for browsing damage, with seedling height and characteristics of the surrounding vegetation being assessed periodically. We found that the most effective treatments at reducing the severity of browsing damage in the short-term (<6 months) were tree guards and a combination of chemical repellent and low nursery fertilizer; there was no effect of the latter after 12 months. These treatments are easily incorporated into existing regimes and, while unlikely to be effective in isolation in areas with high browsing pressure, can be incorporated into management plans to reduce the reliance on lethal controls. While initially less effective than the other treatments, the effects of genetic resistance were more persistent and showed promise for long-lasting protection from browsing.