Tree-ring chronologies for tamarack (Larix laricina (Du Roi) K. Koch) growing in four stand types covering a dry-to-wet gradient were developed to investigate the association between radial growth and climate as well as evidence of larch sawfly (Pristiphora erichsonii Hartig) herbivory near Churchill, subarctic Manitoba. The chronologies, produced using both living and subfossil material, were well replicated for the period 1800 to 2000. Our results indicated that climate explained more than 60% of the growth variation in tamarack with temperature from May to July of the growing season being most important. This was unusual considering that other studies showed a weak radial growth-climate association in tamarack because of signal contamination due to severe larch sawfly defoliation. Potential outbreak episodes were investigated by looking at pointer years and by contrasting the variance within the tamarack tree-ring series with that observed in climate and in nonhost species. A weak correspondence was observed among pale latewood rings, growth suppression period, and incomplete rings. Comparison of host and nonhost chronologies revealed synchronized growth suppression periods in tamarack during 1818–1824, 1857–1864, 1891–1892, 1903–1912, and 1959–1964, with seldom more than 25% of the trees being affected. The 20th-century suppressions corresponded to known outbreaks identified in Manitoba. However, they also corresponded to periods of little residues in the climate model suggesting that they may be due to short-term changes in site hydrology. This study stresses the difficulties to use dendrochronology to identify what may be low severity or “subepidemic” defoliation events. It also stresses the potential differences in the larch sawfly dynamics between the boreal forest and the forest-tundra. Further studies using an extended network of chronologies will be needed to decipher the short-term impacts of climate from those of low severity defoliation episodes.