Host-range testing of a mixture of two nucleopolyhedroviruses of Choristoneura fumiferana (Lepidoptera: Tortricidae)

The host range of a mixture of Choristoneura fumiferana (Clemens) nucleopolyhedroviruses (CfMNPV and CfDefNPV) was investigated using a per os bioassay of larvae of 29 species of Lepidoptera and adult males of Megachile rotundata (F.) (Hymenoptera: Megachilidae). Using a whole-genomic DNA probe, positive results were obtained in 8 of 10 Tortricidae: Archips cerasivorana (Fitch), Choristoneura fractivittana (Clemens), C. fumiferana, Choristoneura occidentalis Freeman, Choristoneura pinus pinus Freeman, Choristoneura rosaceana (Harris), Clepsis persicana (Fitch), and Cydia pomonella (L.); one Crambidae: Ostrinia nubilalis (Hübner); one arctiine Erebidae: Estigmene acrea (Drury); and two Noctuidae: Oligia illocata (Walker) and Pyrrhia exprimens (Walker). Mortality rates were highest among C. fumiferana, C. occidentalis, C. pinus pinus, A. cerasivorana, and C. pomonella. Sequenced polymerase chain reaction (PCR) amplicons from infected individuals from several species confirmed that the primer sets amplified the target viruses. CfMNPV was consistently found in virus-fed C. fumiferana; whereas, CfDefNPV was present only occasionally. The presence of CfMNPV and CfDefNPV in A. cerasivorana was confirmed by PCR and DNA sequencing. Significant treatment-mortality rates were induced in the noctuids P. exprimens and Acronicta impleta Walker; PCR determined that both viruses were present in treated P. exprimens but only CfMNPV was present in A. impleta. No virus was detected in M. rotundata.

The ecological interaction of the mountain pine beetle and jack pine budworm in the boreal forest

As climate change facilitates the range and host expansion of insect species into new ecosystems, the development of newstrategies for managing and preventing biological invasion is receiving considerable interest. In recent years, the range ofthe mountain pine beetle (Dendroctonus ponderosae Hopkins) has expanded from lodgepole pine-dominated forests eastof the Rocky Mountains into lodgepole x jack pine hybrid forest of western Alberta, and may soon invade jack pine forestsof the boreal. Our understanding of factors contributing colonization of jack pine by mountain pine beetle is far fromcomplete and several factors may limit its spread in these forests, including tree resistance and competitors. Among these,the jack pine budworm (Choristoneura pinus pinus Freeman) is one of the most important insect enemies of jack pine andan outbreak defoliator that potentially weakens jack pine trees, which may make them more susceptible to MPB attacks.To develop effective management strategies in the face of the short-run impacts of climate change, we need an in-depthunderstanding of factors influencing establishment and survival of the beetle in jack pine forests.Key words: Choristoneura pinus pinus, Dendroctonus ponderosae, jack pine, range expansion, invasion biology, climatechange in the boreal forest, conifer-mediated interactions, tree induced defences, tripartite interactions

FEEDING BEHAVIOUR OF THE FIRST-INSTAR CHORISTONEURA FUMIFERANA AND CHORISTONEURA PINUS PINUS (LEPIDOPTERA: TORTRICIDAE)

We have discovered that, contrary to the long-held belief, 1st-instar spruce budworm, Choristoneura fumiferana Clemens, do feed. They display red alimentary tracts if they are provided with diet containing the red dye amaranth. They graze on the surface of balsam fir needles sprayed with rhodamine and ingest the fluorescent material, which can be detected in the frass pellets deposited inside the hibernacula. When emerging 1st instars were allowed to crawl on the inside surface of a glass tube coated with the polyhedral inclusion bodies of a recombinant C. fumiferana virus containing the gene for the green fluorescent protein, the larvae showed the characteristic green fluorescence, indicating that not only had they ingested the occlusion bodies but also the virus had replicated and infected different tissues. Similar results were obtained with the jack pine budworm, Choristoneura pinus pinus Freeman, which has an identical life history. The advantages of early-instar intervention to minimize defoliation by using control agents such as the ecdysteroid agonist, tebufenozide (RH-5992, Mimic® formulation), are discussed.

Association of within-tree jack pine budworm feeding patterns with canopy level and within-needle variation of water, nutrient, and monoterpene concentrations

The possibility that uneven within-tree feeding patterns by jack pine budworm (Choristoneura pinus pinus Freeman) larvae could be related to underlying variation in host jack pine (Pinus banksiana Lamb.) foliar water, nutrient, and monoterpene contents was considered. Choristoneura pinus pinus feeds disproportionately in the upper portion of the canopy and almost exclusively on the basal portions of needles. Within needles, the distribution of water, several nutrients, and monoterpenes varied significantly between the distal and basal sections. Water, nitrogen, sulfur, manganese, and zinc levels occurred in higher concentrations in the distal section of the needle, which would not be predicted based on C. pinus pinus feeding patterns. Phosphorus, potassium, calcium, iron, and copper were significantly higher in the basal section. Although the latter differences might be predicted based on C. pinus pinus feeding patterns, they were not strong (ranging from 7.8% to 36.4% relative differences, as compared with 10.7%-50.0% relative differences in the former group). By contrast, concentrations of foliar monoterpenes were more strongly associated with known feeding patterns of C. pinus pinus. These relative differences ranged from myrcene (26.8%) to limonene (44.79%). Thus, foliar differences affecting within-needle feeding selection appear more associated with allelochemicals than nutrients or water. In contrast with the within-needle associations between larval feeding and foliar chemistry, no associations between upper and lower canopy foliage were observed. Water, nutrients, and monoterpenes were evenly distributed across the upper and lower canopy locations. Thus, differential feeding between canopy locations cannot be explained by foliar constituents. Rather, it is more likely explained by other environmental factors, such as proximity to and density of reproductive and vegetative shoots.