Epidemiology of the southern pine bark beetle guild /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | The role of disturbance in the initiation and growth of infestations of the southern pine bark beetle guild (Dendroctonus frontalis Zimmerman, D. terebrans (Olivier), Ips calligraphus (Germar), I. grandicollis (Eichhoff), I. avulsus (Eichhoff)) was investigated. The objective of this study was to test the hypotheses that: (1) lightning-struck trees are recognized and responded to by the bark beetle guild, (2) lightning-struck trees provide refuge for bark beetles, (3) refuge trees serve as epicenters for infestations, (4) trees show qualitative changes in phloem chemistry in response to disturbance, and (5) ovipositing and developing bark beetles respond to the variations in nutrient quality of their host. 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. Trees disturbed in spring, summer, and fall trials were colonized within two weeks after the disturbance. All species of the bark beetle guild were involved in the colonization process. These results supported the hypotheses that disturbed trees are responded to by the bark beetle guild and that these disturbance centers often serve as foci for infestation development. Percent of the arriving population that colonized the trees ranged from 9-41 for D. frontalis and 8-59 for I. calligraphus. Most D. frontalis and I. calligraphus attacked on the day they arrived. However, I. calligraphus tended to show a longer delay between arrival and attack than D. frontalis. The low attack densities in the study trees supported the hypothesis that disturbance centers serve as refuges for bark beetles. Also, the behavior of the beetles during colonization of the refuge tree was interpreted to be conducive to infestation growth. Chemical composition of the phloem was influenced primarily by the time of year, rather than by the disturbance event. Nitrogen and sugar concentrations were not correlated to reproduction parameters of either species. Sugars were positively correlated with emergence densities and pronotal width of brood beetles of both species and with survivorship of D. frontalis. These results indicate that bark beetles do respond to the nutrient quality of their host. Also, the fact that season, and not disturbance, had the greatest influence on nitrogen and sugar concentrations suggests that the role of lightning-struck trees is not one of providing beetles with a resource of superior nutrient quality, but rather the formation of a well dispersed and dense array of susceptible trees. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Entomology." |
| Physical Description: | xii, 88 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |