Effectiveness of repellents for reducing damage to eucalypt seedlings by browsing mammals

Abstract

Marsupial herbivores cause significant damage to seedlings in forestry operations. Damage can lead to changes in tree form, reduced growth rates and seedling death. Non-lethal tactics, as a component of an integrated browsing management strategy, are currently sought to assist in reducing this amount of damage. One such tactic involves making seedlings deterrent or unpalatable through the application of chemical repellents. We investigated the effect of three chemical repellents, Plant Plus, Sentree and Hot Shot, upon browsing of Eucalyptus nitens seedlings by two marsupial herbivores known to browse newly established plantations in Tasmania; the common brushtail possum and the red-bellied pademelon. One repellent was designed to deter herbivores through an unpleasant odour (Plant Plus), one to be unpalatable (Hot Shot), and the third to be both deterrent and unpalatable (Sentree). We ran a combination of paired feeding trials (one repellent + control) and cafeteria trials (all three repellents at once with no control) with captive possums and pademelons, for three nights per trial. Both species consumed significantly more foliage from control seedlings than those treated with Plant Plus or Sentree repellents. Pademelons also preferred controls to Hot Shot treated seedlings but, interestingly, possums consumed significantly more foliage from seedlings treated with Hot Shot than control seedlings. The most effective repellent against both herbivores was Sentree, and the marked reduction in browsing indicates that further testing in the field is warranted.