Response of the Southern Pine Bark Beetle Guild (Coleoptera: Scolytidae) to Host Disturbance

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Abstract
Role of host disturbance in initiation and growth of infestations of the southern pine bark beetle guild [Dendroctonus frontalis Zimmermann, D. terebrans (Olivier), Ips calligraphus (Germar), I. grandicollis (Eichhoff), and I. avulses (Eichhoff)] was investigated. Host loblolly were disturbed at four intervals throughout the year and response of the bark beetle guild was monitored. Effects of the disturbance were evaluated by assessing tree mortality resulting from colonization by the bark beetle guild. Numerical responses of beetles to treatment and control trees were measured and the structure of the populations was defined in terms of proportions of the different species responding to the disturbance. All disturbed hosts were discovered and colonized by the bark beetle guild. Multiple-tree infestations developed from 10 of 20 treatment centers. Trees disturbed during the winter persisted as foci for beetle colonization for 133–150 days. The disturbance event did not have to coincide with seasonal development of the bark beetle guild for the hosts to be utilized for colonization. Trees in spring, summer, and fall treatments were colonized immediately after the disturbance. All species of the bark beetle guild were involved in the colonization process. However, structure of the populations (species composition and numbers) was different during the four seasonal treatments. Results of the experiment are interpreted in the context of the hypothesis that lightning, acting as a disturbance, is an integral component of the natural history of the bark beetle guild. The study provides experimental evidence to support the major tenets of the hypothesis.