SBW AIDD. Developing an adaptive and intelligent defoliation detector. Adaptive deep and transfer learning to predict tree level SBW annual and cumulative defoliation at various platforms
Defoliators like spruce budworm (SBW) damage trees by eating young needles that emerge early in the growing season. Consecutive repeated attacks removing photosynthetic material impact growth and gradually may result in mortality (MacLean and MacKinnon 1996). Periodic outbreaks are known to affect more territory than fire or forest harvesting in Europe and North America significantly impacting their ecology and economy (Fei et al 2019, NRCan 2016). Hence detection of the early signs of their impacts can help in effective planning of response strategies to control insect spread and minimize the impact on the forest industry (MacLean et al 2019, Liu et al 2019, Nidiquet et al 2016).
The feeding debris created by SBW during bud-burst (late June-early July) that gets entangled in the silken web, generally concentrated towards the top canopies, gives a reddish brown appearance. This short window of opportunity of discoloration is the only visual indication of the annual damage perceivable on large spaces, especially from above the canopy. Operationally available annual aerial surveys conducted by provinces in Canada utilise this narrow opportunity to map annual extent and broad level of severity of defoliation (MacLean et al 1996). Unlike bark beetles whose impact could be seen through predominant discoloration of foliage and eventually a rapid death, cumulative impact of defoliation is a gradual process and discoloration is not visibly evident on lightly defoliated trees. Assessment of annual surveys was found to be less accurate in discriminating light from very light/nil defoliation (MacLean et al 1996). In addition, defoliation being the amount of the chewed, mined or missing needles, unless the tree has moderate amount of bare woody parts, estimation of the cumulative defoliation outside the narrow time window, after opening of the buds, is challenging.
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