Verbenone Plus Reduces Levels of Tree Mortality Attributed to Mountain Pine Beetle Infestations in Whitebark Pine, a Tree Species of Concern

Christopher J Beverly M

doi:10.4172/2155-6202.1000123

Abstract

In western North America, recent outbreaks of the mountain pine beetle, Dendroctonus ponderosae Hopkins, have been severe, long-lasting and well-documented. We review previous research that led to the identification of Verbenone Plus, a novel four-component semiochemical blend [acetophenone, (E)-2-hexen-1-ol + (Z)-2-hexen-1- ol, and (–)-verbenone] that has been demonstrated to inhibit the response of a closely-related bark beetle species, western pine beetle, D. brevicomis LeConte, to attractant-baited traps and trees. In this study, we evaluate the efficacy of Verbenone Plus for protecting stands of whitebark pine, Pinus albicaulis Engelm., a species of concern being considered for listing as a threatened and endangered species, from mortality attributed to D. ponderosae infestations in the central Sierra Nevada, California, USA. The experimental design was completely randomized with two treatments (untreated control, Verbenone Plus) and four replicates (0.4-ha square plots) per treatment. A total of 450 trees were killed by D. ponderosae, 377 were P. albicaulis and 73 were lodgepole pine, P. contorta Dougl. ex Laws. Significantly, fewer pines (P. albicaulis and P. contorta) and P. albicaulis (only) were killed by D. ponderosae on Verbenone Plus-treated plots compared to the untreated control. On average, there was ~78% reduction in tree mortality attributed to Verbenone Plus. We discuss the implications of these and other results to the development of Verbenone Plus as a semiochemical-based tool for tree protection.

Highlights

Recent outbreaks of mountain pine beetle, Dendroctonus ponderosae Hopkins, have been severe, long-lasting and well-documented [1]
The objective of this study was to determine the effectiveness of Verbenone Plus for protecting P. albicaulis from mortality attributed to D. ponderosae in California, USA
Of the 450 trees that were killed by D. ponderosae, 377 were P. albicaulis and 73 were P. contorta

Summary

Introduction

Recent outbreaks of mountain pine beetle, Dendroctonus ponderosae Hopkins, have been severe, long-lasting and well-documented [1]. Dendroctonus ponderosae ranges throughout British Columbia and Alberta, Canada, most of the western USA, into northern Mexico, and colonizes several pine species, most notably, lodgepole pine, Pinus contorta Dougl. Ex Laws., sugar pine, P. lambertiana Dougl., limber pine, P. flexilis E. Whitebark pine, P. albicaulis Engelm.[2]. Episodic outbreaks of this notable pest are a common occurrence, but the magnitude and extent of recent outbreaks have exceeded the range of historic variability, and have occurred in areas where D. ponderosae outbreaks were once rare (e.g., P. albicaulis forests) or previously unrecorded (e.g., jack pine forests, P. banksiana Lamb.) [1,2,3,4]

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