Canadian Forest Service Publications

Management strategies for forest insect defoliators in British Columbia. 1994. Shepherd, R.F. Forest Ecology and Management 68: 303-324.

Year: 1994

Issued by: Pacific Forestry Centre

Catalog ID: 3556

Language: English

Availability: PDF (request by e-mail)

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In a synthesis of outbreak characteristics of common defoliating insects in British Columbia, two types emerge: those with fast-cycling outbreaks and those with sustained outbreaks. Species with fast-cycling outbreaks rise quickly to visible defoliation levels, cause significant growth loss, tree deformation and mortality, and disappear just as quickly. Impact is closely related to the severity of defoliation during the first year of an outbreak; consequently, the objective of managing these species should be to reduce populations before defoliation occurs, i.e. to prevent the outbreak. To accomplish this objective, identification of susceptible habitats and monitoring with sensitive pheromone traps in areas of expected outbreaks are necessary to detect upwelling populations. Species with sustained outbreaks cause significant growth losses only after defoliation continues for a number of years. Tree mortality usually is not important except where regeneration is being nurtured under a selective or shelterwood silvicultural system. Impact can be significant over the life of a stand because of the length and frequency of outbreaks, but treatments effective for only 1 year usually cannot be justified except where it is important to retain a full crown. Long-term cultural methods appear to be the preferred management system and, of these, utilizing non-host species or resistant or phenologically asynchronous host species may be the best option. Again, determining the location of expected outbreaks is an important component of a management system and, at present, identifying stands by frequency of outbreak within zones of climatic suitability would be useful in selecting treatment areas.