Sugar maple decline after defoliation by forest tent caterpillar

Defoliation is a significant stressor of forest stands that may incite decline disease of sugar maple (Acer saccharum: Marsh). The recent outbreak (2002-2007) of forest tent caterpillar (FTC; Malacosoma disstria: Hübner) in the northeastern United States offered the opportunity to assess the effects of defoliation and site conditions on sugar maple health. We measured 51 North American Maple Project stands in New York and Vermont in the summer of 2007. Dieback (P = 0.07) and mortality (P = 0.04) were both worse in stands defoliated by FTC. Low growing-season soil moisture during the outbreak, indicated by Palmer's Z-index; cool mean temperature during the outbreak; and concave microrelief were also important predictors of forest damage. We present the results of our multiple regression equations for stand dieback (R ² = 0.71) and mortality (R ² = 00.64) in tables that can be used by forest managers to evaluate the vulnerability of their sugar maple stands to decline after defoliation by FTC.