Effects of defoliation by the leaf beetle,Chrysophtharta bimaculata, on growth ofEucalyptus regnansplantations in Tasmania

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Abstract
Defoliation of Eucalyptus regnans plantations in Tasmania by the leaf beetle Chrysophtharta bimaculata (Olivier) over a two year period significantly reduced growth of one-year-old previously uninfested trees and six-year-old trees with a history of defoliation. One-year-old trees defoliated by C. bimaculata had lost 45.6% and 52.1% of their potential height increment and basal area increment respectively by the end of the two year trial compared to protected trees. Six-year-old trees experienced similar growth losses and the biomass of leaves and stems/branches of unprotected trees at the end of the two year period was reduced by 44% and 39% respectively compared to protected trees. The impact of the defoliation levels recorded in these trials is discussed in relation to the current control strategy for C. bimaculata and the economics of eucalypt plantations in Tasmania.