There are several factors that have allowed the spruce
budworm to not only persist, but even to thrive in some areas, despite spray campaigns.
One such factor is the budworm's great ability to disseminate. The spruce budworm can
travel great distances as a winged adult, but the larvae also can travel, by spinning
silken threads and catching the wind. Hence spraying is not effective unless very large
areas are sprayed simultaneously, which is difficult to
coordinate.
In the last century, logging practices and
forest fire suppression have changed the distribution of spruces. In the primeval
forests of North America, spruce was mainly limited to cooler, damper areas, and pine
and hemlock occupied the areas between spruce stands, which naturally limited outbreaks
of budworm. Currently spruce are growing up in areas formerly limited to other species,
creating larger contiguous areas of spruce which allow the budworm to get a good
foothold.
Current research is looking at integrated pest
management techniques which will help to limit the need for spraying, which has negative
impacts on entire ecosystems when widely used.
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