Relative Suitability of Virginia Pine and Loblolly Pine as Host Species for Dendroctonus frontalis (Coleoptera: Scolytidae)
Dendroctonus frontalis is a major disturbance agent in American pine forests, but attack preferences for various host species, and their relative suitability for reproduction, are poorly knowi). We studied patterns of beetle attack and reproduction during an infestation of stands contairiing Virginia pine and lol~lolly pine. Nearly all Virginia pine were attacked and killed, whcrcas n third of the loblolly pine escaped attack. Among attacked trees, the density of landings and attacks on Virginia pine was 56-106% higher than on loblolly pint at one site, whcrcas it was similar between species at another site. Paradoxically, D. frontalis preferred the host that was least suitable for reproduction: mean ±SE = 0.89 ± 0.33 versus 4.65 ± 1.40 progeny attack in Virginia pine versus loblolly pine. Poor reproduction in Virginia pine was attributable to increased adult mortality, decreased oviposition, and decreased larval survival. Phloem thickness and nitrogen content were similar between the two pine species. Loblolly pine was significantly more suitable for the growth of Ophiostoma minus, a fungal associate of D. frontalis. Resin flow was lower in Virginia pine than in loblolly pine. although oleoresin chemistry may partly explain poor reproduction in Virginia pine. A simulation motlcl prcdictctl that beetle inftdations will tend to collapse within stands dominated by Virginia pine, and that increasing availalility of loblolly pines will promote infestation growth. Because of beetle preferences, forests that contain even modest proportions of Virginia pine relative to loblolly pine may be less likely to sustain betIe infestations. Management of species composition may provide a means for mitigating the undesirable impacts of this herbivore in pine forests.
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