Title page for ETD etd-04292010-151532


Type of Document Master's Thesis
Author Story, Heather Marie
Author's Email Address sheather@vt.edu
URN etd-04292010-151532
Title Assessing performance and compatibility of three Laricobius species as predators of hemlock woolly adelgid, Adelges tsugae.
Degree Master of Science In the Life Sciences
Department Entomology
Advisory Committee
Advisor Name Title
Kok, Loke T. Committee Co-Chair
Salom, Scott M. Committee Co-Chair
Bergh, J. Christopher Committee Member
Mullins, Donald E. Committee Member
Keywords
  • biological control
  • Laricobius
  • competition
  • density-dependence
Date of Defense 2010-05-19
Availability restricted
Abstract
Predation, egg production and survivorship of Laricobius nigrinus Fender, L. rubidus, LeConte, and L. osakensis Montgomery and Shiyaki (proposed), predators of hemlock woolly adelgid, Adelges tsugae, Annand, were investigated in the laboratory and in the field. In individual assays, L. rubidus oviposited fewer eggs than either L. nigrinus or L. osakensis. In assays containing congeneric or conspecific groups of adult Laricobius, L. osakensis preyed upon the greatest number of ovisacs. When all three species were together, the numbers of ovisacs preyed upon were similar to the mean of all three individual species. Adult predators fed on few eggs and did not exhibit any species preference. The numbers of A. tsugae ovisacs fed upon did not differ significantly by groups of congeneric or conspecific Laricobius larvae. Laricobius adults and larvae had high survival rates throughout all experiments. In the field, predators were enclosed in sleeve cages with both high (> 120 ovisacs) and low (< 90 ovisacs) A. tsugae densities for 1 wk. All branches with caged beetles had significantly greater numbers of ovisacs preyed upon than branches caged without beetles. No differences in predation or egg production were found among the conspecific and congeneric groupings. Predation was uniformly higher at the high prey-density than at the low prey-density. Survivorship among predators did not differ significantly at either prey density. Results from both laboratory and field experiments suggest that these species are able to co-exist and can be in the same location for biological control of A. tsugae.

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