Abstract
Pyrgoides orphana (Erichson) severely defoliates large areas of silver wattle (Acacia dealbata Link) in Tasmania, particularly in the Florentine Valley region. Attacked trees are often completely stripped of all foliage during the winter months by the larval stages of this beetle. The life history of P. orphana is described and an account of the effect of defoliation on growth of silver wattle over an 18 year period is presented. There is a marked reduction in height increment following P. orphana outbreaks and repeated defoliation has killed many trees. Diameter growth has been retarded and no increment has occurred in the period 1974–77. The significance of P. orphana is discussed in relation to its direct effect on the growth of silver wattle and the possible secondary effects of reducing competition of wattle with other commercial forest species.

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