Biology and ecology of root-feeding beetles and ophiostomatoid fungi in sandhills longleaf pine stands

Abstract

Ophiostomatoid fungi, especially those of the genus Grosmannia Goid. and its Leptographium Lagerb.& Melin anamorphs, are vectored by beetles and have been implicated as factors in decline of loblolly pine (P. taeda L.) and longleaf pine (P. palustris Mill.). In this dissertation the biology and ecology of ophiostomatoid fungi and their vectors were studied in longleaf pine stands at Fort Benning and a loblolly pine decline risk model tested for its ability to predict areas of symptom development in longleaf pine. Longleaf pine data included tree height and diameter, increment growth, crown characteristics, and standing resin reserves. Longleaf pine roots were excavated and assayed for Leptographium infection. Root-feeding insects were collected using pitfall traps and assayed for Leptographium infestation. Differences in growth parameters were observed only in the 20-40 year age class between predicted symptomatic and predicted asymptomatic plots. Trees in all age classes were found to be infected with Leptographium procerum (Kendr.) Wingfield and L. terebrantis Barras & Perry, but infection had no effects on growth or crown variables. Leptographium distribution in longleaf pine roots was not as predicted by the loblolly pine decline risk model. Grosmannia huntii (Robinson-Jeffrey & Grinchenko) Zipfel, de Beer & Wingfield was isolated from a single symptomatic longleaf pine tree. Peak numbers of beetle captures and fungal infestation varied by insect species and by collection season. Grosmannia huntii, L. procerum, and L. terebrantis were the predominant fungi on Hylastes spp. Erichson. The presence of G. huntii and L. serpens (Goid.) Siemaszko in the southeastern United States was confirmed by DNA sequence analysis, and molecular and morphological data are presented to aid in differentiation. An Ophiostoma sp. Syd & P. Syd isolated from declining loblolly pine roots and root-feeding beetles in this dissertation is described as a novel species, O. sparsiannulatum Zanzot, de Beer & Wingfield.