Modification of native baculoviruses; efficacy, characterization and ecological risk assessment

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Canada's major forest resource provides an enormous capacity to sequester carbon dioxide emissions, an important component of the Kyoto agreement but only if that resource is properly protected from the major forest insect pests such as the spruce budworm and tent caterpillar. Protection of our forests would also directly benefit the forest industry, responsible, in 2001, for a $28 billion GDP, a $34 billion trade balance and sales of $74 billion. However, protection must be sustainable and environmentally benign, focusing on the specific pest species. CfMNPV is a natural biological agent specific to the spruce budworm, Choristoneura fumiferana, historically the major defoliator in Canada's boreal forest and responsible for damage to 1 to 50 million hectares per year. To make this native virus more effective at controlling this pest, we intend to incorporate small pieces of genetic information, borrowed only from within the virus-caterpillar ecosystem, into the CfMNPV genome. For example, we intend to reprogram the virus to produce proteins that will damage spruce budworm, like viral cathepsin and chitinase, at times earlier, and at higher levels than in the native virus. Genes for spruce budworm regulatory proteins will also be incorporated so that their production by the virus will disrupt the insect's normal development and lead to behavioural changes such as cessation of feeding.  Both strategies should be environmentally benign since they utilize only genetic material indigenous to the natural ecosystem. The activity and efficacy of the modified variants will be characterized under different environmental conditions (e.g. dosage, kill times, reduction in feeding damage) to identify those providing improved protection.  These data, together with additional studies on host range, transmission, persistence and  competitiveness with the native virus, will be used to assess the potential ecological impact of the modified viruses. Our approach does not alter the existing forest "gene pool", but is expected to provide better control agents against this significant pest. Our research could be expanded to the forest tent caterpillar (1 to 24 million ha damage). Moreover we will also evaluate a similar approach for use against agricultural pest insects.