Mountain pine beetle (MPB) is the most damaging insect of mature pine forests in western North America. The current outbreak in British Columbia is the largest ever recorded. During a survey of beetle occurrence, well—established infestations were sampled in central B.C. and found to possess larval mortality. Bacteria or other microbes were among the potential causes of the mortality. Bacteria were isolated from living larvae and adults, as well as larval and adult beetle cadavers found in bark samples. Bacteria were identified by fatty acid methyl ester (FAME) analysis, which indicated 32 species of bacteria present in the MPB laivae. The predominant bacteria ( Serratia liquefaciens , S. plymuthica ) were detected in about a third of all sampled laivae, regardless of mortality. Rahnella aquatilis was found in 11% of all larvae examined and was usually (93%) associated with laival mortality. Interactions between two bluestaining fungal symbionts of the MPB ( Grosmannia clavigera , Ophiostoma montium ) and two of the isolated bacteria ( S. liquefaciens and R. aquatilis ) were assessed. S. liquefaciens and R. aquatilis both inhibited the growth of beetle-associated bluestain fungi by 72%. The bluestain fungi did not impede bacterial growth, and both bacteria grew on autoclaved bluestain mycelium. Combinations of the two bacterial species formed aggregates on practical-grade (crab) chitin, but there was no aggregation in pure cultures or on the autoclaved mycelium of G. clavigera or O. montium . These results indicated that the two bacteria may be capable of aggregation within the insects, and this may have implications for their combined effects in the beetle. The role of S. liquefaciens and R. aquatilis in MPB biology requires further investigation.

Abstract This chapter focuses on weedy hardwood trees, maples (Acer spp.), alders (Alnus spp.), birches (Betula spp.), poplars (Populus spp.) and cherries (Prunus spp.) that pose a problem endemic to conifer regeneration sites following harvest in plantations in Canada. It provides an overview of the fungi (including Chondrostereum purpureum) that have been tested for the management of these weedy hardwood trees, and brief notes on competitive interactions. Future research prospects are recommended.

Calamagrostis canadensis, commonly called bluejoint or marsh reed grass, has become a serious competitor of forest regeneration in western boreal Canada. Bluejoint is a perennial, rhizomatous grass native to North America, growing up to 2 m tall from creeping rhizomes. It is a pioneer species and can increase greatly in abundance following disturbances such as fire, flooding, insect outbreak, windfall or timber harvesting. Harvesting often results in the establishment of an herbaceous community dominated by C. canadensis, particularly on moist rich sites characteristic of the region. In the absence of shade, this grass can form continuous dense stands and develop a heavy, deep thatch. A bluejoint-dominated disclimax community may persist for 25 to 100 years or more, limiting reestablishment of other plant species and altering forest succession. However, without further disturbance, C. canadensis more often loses dominance of sites within 10 to 20 years. With the development of a woody shrub and tree canopy, the grass will die back and eventually become fairly inconspicuous as a forest understory species.

Red alder (Alnus rubra) is a valuable timber tree on 10-20% of forested lands in Pacific Coastal North America and is an undesirable competitor of planted conifers, to a greater or lesser extent, on much of the remainder. A biological control strategy to manage red alder was developed for use in environmentally sensitive areas in which pesticides are prohibited by law, and as a complement to extant weed control measures. Red alder trees within a typical west coast forest were inoculated with pathogen-colonized wood dowels inserted into stem punctures, using technology designated PFC-MYCOCHARGE(R). Each of 11 blocks of 30 trees (6 per diameter class, 0.5 cm to approximately 50 cm diam) was inoculated with 1 of 11 isolates of seven species of Ascomycotina previously isolated from red alder in British Columbia. A 12th block of 30 trees was treated with noncolonized dowels and designated the control block. A single isolate of Nectria ditissima (PFC-082/ATCC 74260; U.S. Pat. Off. 5 340 578)) proved worthy of commercial development by virtue of nearly 100% inoculation success, notable alder tissue damage, and reduction in general health of inoculated trees. A significant relationship between pathogen species and mortality was not recorded during the limited period of the test. N. ditissima PFC-082 did not reproduce on the trees and was soon displaced by secondary organisms, so the danger of unwanted dispersion of the pathogen was nil. The PFC-MYCOCHARGE(R) strategy is recommended for commercial development as a component of forest management plans for implementation during pre-commercial stand improvement activity.