Mountain pine beetle associated blue-stain fungi cause lesions on jack pine, lodgepole pine, and lodgepole × jack pine hybrids in Alberta

Abstract

Mountain pine beetles ( Dendroctonus ponderosae Hopkins; (MPB)) have spread into lodgepole × jack pine hybrid ( Pinus contorta Douglas × Pinus banksiana Lambert) forests in Alberta and are predicted to spread into jack pine forests. Their success in these forests is uncertain but will be influenced by multiple factors, including the ability of their associated blue-stain fungi to colonize the trees and the health of the encountered trees. Healthy and dwarf mistletoe infected pines at three sites across Alberta (one site per pine species) were inoculated with three isolates each of Grosmannia clavigera (Robinson-Jeffrey and Davidson) Zipfel, de Beer and Wingfield and Ophiostoma montium (Rumbold) von Arx. Both fungi grew and caused lesions on all hosts, suggesting that MPB will not be limited by a lack of fungal growth. Both fungi caused longer lesions in jack and hybrid pines than in lodgepole pines, indicating that susceptibility varies among hosts and is greater in the novel systems than in the co-evolved one. G. clavigera caused longer lesions than O. montium in hybrids and lodgepole pines, while the two species caused similar-sized lesions on jack pine. Intraspecific variation was high in G. clavigera, with one isolate producing much shorter lesions than the other two. Dwarf mistletoe infestation had little effect on infection lesion length.

Stimulation of tree defenses by Ophiostomatoid fungi can explain attack success of bark beetles on conifers

“…They thus certainly coexist also within the same beetle population. Similar results have been obtained among isolates from different localities, with O. bicolor and O. piceaperdum associated with I. typographus (Sallé et al, 2005) and with G. clavigera associated with D. ponderosae Rice et al, 2007a). In the latter association, variations among isolates in their adaptation to cold temperature have also been reported (Rice et al, 2008).…”

Effect of Water Stress and Fungal Inoculation on Monoterpene Emission from an Historical and a New Pine Host of the Mountain Pine Beetle

“…Lodgepole pine is one of the historical hosts of MPB in Western Canada, however, as its range expands from its historical habitat to new areas in northern Alberta (Carroll et al, 2006), MPB has spread across the lodgepole×jack pine hybrid zone into stands of pure jack pine (Cullingham et al, 2011). Studies show that beetles can reproduce and develop in jack pine (Cerezke, 1995), as do its fungal associates (Rice et al, 2007). Jack pine is the most abundant pine species in the boreal forest which potentially could lead to the spread of MPB across the boreal forest to eastern Canada.…”

“…At least two MPB associated blue stain fungi, Grosmannia clavigera and Ophiostoma montium, also deplete tree defenses and kill their host (Reid et al, 1967;Rice et al, 2007) during the host colonization process. Grosmannia clavigera is more virulent than O. montium (Yamaoka et al, 1990) and often is used experimentally to stimulate tree defenses (Reid et al, 1967;Lieutier et al, 2009).…”

Impacts of insect outbreaks on tree mortality, productivity, and stand development

“…Mountain pine beetles attack pine trees by laying eggs under the bark and larvae mine the phloem and eventually cut off the tree's supply of nutrients. Mountain pine beetles also carry up to three species of symbiotic ophiotomatoid fungi that inhibit tree natural defenses against beetle attacks and also shut down water transport (Rice et al 2007a(Rice et al , 2007b. Mountain pine beetle is generally specific about the age classes it attacks and kills, resulting in a clear impact on the age distribution of trees, even more so than with spruce budworm.…”