Evaluation of (S)-Verbenone Applications for Suppressing Southern Pine Beetle (Coleoptera: Scolytidae) Infestations

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Abstract
Field tests were conducted to evaluate the efficacy of various applications of the beetle-produced, inhibitory compound (S)-verbenone for suppressing infestations of the southern pine beetle, Dendroctonus frontalis Zimmermann. Twenty-four expanding infestations (spots), ranging in size from 22 to 140 active trees, and representing a variety of stand conditions, were treated with one of five different applications. Treatments included: (A) (S)-verbenone applied at the rate of 4 ml per tree, (B) (S)-verbenone applied at 8 ml per tree, (C) (S)-verbenone at 8 ml per tree in combination with felling all freshly-attacked trees, and the preliminary treatments; (D) (S)-verbenone in combination with the attractant frontalin, and (E) (S)-verbenone plus frontalin, plus felling all infested trees. In all treatments, (S)-verbenone was mixed with a sustained release liquid polymer and applied to a horseshoeshaped buffer of uninfested trees at the advancing head of the infestation. To draw emerging beetles away from the advancing head, in Treatments D and E, frontalin, a beetle-produced attractant, was applied in the center of the infestation to nonhost trees or to host trees previously infested by beetles. To measure treatment efficacy, rates of spot growth following treatment were compared with pretreatment infestation growth rates. Observed rates of spot growth before and after treatment were compared with spot growth projections generated by a southern pine beetle spot growth prediction model. Results showed that Treatment C was the most effective and practical treatment tested. Spot growth in all five infestations treated with this application was completely halted with few or no additional trees being attacked. Treatment B proved relatively effective in slowing rates of spot growth in small or moderate-sized spots. Treatment E was effective in completely halting spot growth in two large infestations in sawtimber stands, but the treatment required the use of two behavioral chemicals. Treatments A and D were less successful in disrupting spot growth than the other treatments.