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Few attempts have been made to quantify the damage to agricultural crops resulting from known densities of a particular pest. Availability of such information, even in its most basic form, is essential to making cost-effective management decisions. The question seems straightforward and simple; however, it is neither. For example, the damage caused by rodents in an apple orchard is not easily observed or measured. Moreover, the ultimate economic effects are dependant to s.ome degree upon tree age, variety and replacement cost; weather, productivity market prices, and a host of other manageable and unmanageable factors facing the grower. In addition to these variables we must admit to not knowing exactly how the degree of girdling damage relates to health and vigor of the tree nor do we understand cumulative or recuperative factors which likely affect a perennial species. We do have evidence that compensatory growth can occur in certain damage situations (see for example Dyer 1973, 1975, 1976; Harris 1974; Hutchinson 1971; Pearson 1965; Vickery 1972; Westlake 1963 and Woronecki et al. 1976). So, while the problem appears clear the answer can be obfuscated by a host of variables many of which can change in a single season.