Insect-Nematode-Red Pine Association in Western Maryland with Major Emphasis on Bursaphelenchus xylophilus and Monochamus spp.

Abstract

Western Maryland red pines, Pinus resinosa Ait. Were examined over three years, 1982-1984, to determine the distribution of Bursaphelenchus xylophilus, the pinewood nematode. Ca. 47-year-old (older) and ca. 25-year-old (younger) trees were subdivided into the following categories: (1) trees with mostly green needles; (2) trees with mostly reddish-brown needles; (3) trees with no needles but with bark intact; (4) trees with no bark; and (5) trees with chlorotic, bleached-green needles. The pinewood. nematode infected 76.5% of older red pines and 68% of younger red pines. The nematode was not evenly distributed in trees in any tree decadence category or by tree age. Bursaphelenchus xylophilus infected 15.1% of the samples from trunk, primary and secondary branches in older red pines and 18.5% in younger red pines. By tree decadence category older trees had the highest infection (25.2%) in green needled trees (category 1) whereas younger trees had the highest infection (28.7%) in bleached-green needled trees (category 5). Trees collected in late May-early June 1982 lacked Monochamus rearings and belonged to categories 1, 2, 3 and 4. Trees from these categories had emergences of Ips spp., Tetropium schwarzianum Casey, Pissodes approximatus Hopkins and Otiorhynchus spp. in summer 1982. From bleached-green needled red pines (category 5) collected in late July-early August 1983 two Monochamus species emerged in 1984, M. carolinensis (Olivier) and M. scutellatus (Say), as well as other insects including Neacanthocinus pusillus (Kirby) and Amniscus collaris Haldemann. Chrysobothris scabripennis Cast. and Gory emerged from trees cut in 1983, but which remained uncaged in the field until 1984. Bursaphelenchus xylophilus was present in 94% of tracheal systems of both M. scutellatus and M. carolinensis. Pinewood nematode was found infesting 4.2% of N. pusillus specimens. One specimen each off. approximatus, Ips spp. and C. scabripennis were positive for B. xylophilus. Dolichomitus tuberculatue tuberculatus (Geoff.), an ichneumonid parasite, was reared from Monochamus spp. larvae. Two deutonymph mites, Dendrolaelap isodentatus (Hurlbutt) and Trichouropoda hirsuta Hirschmann, were located externally on Monochamus spp. beetles.