Full- and half-strength Silvisar 510 injected trap trees gave mortalities of 94 and 90%, respectively, for Dendroctonus rufipennis (Kirby). Half-strength treated trees received more attacks and also had lower arsenic concentrations in the phloem and cones than did the full-strength treatments. The tenth and quarter-strength treatments resulted in spruce beetle mortalities of 40 and 70%, respectively. Injection of trees in late August, followed by felling one mo later, is preferable to earlier or later injection and felling times.
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Lister et al. (1976) studied this question.