From: Hubbard Brook.org
Sugar maple decline
Sugar maple across the northeastern US and eastern Canada have been exhibiting an increased incidence of decline in recent years. Sugar maple decline is not a disease with specific causal agents, but a series of events that eventually leads to the death of the tree. It has been around for decades but has not been considered a widespread problem until recently. The exact causes of sugar maple decline seem to vary with site are therefore hard to pinpoint. Symptoms include reduced foliage and reduced twig growth, and then dieback of branches in the upper canopy. The photos above show a sugar maple with crown die-back and a close-up of dead branches in the crown.
In a forested environment, sugar maple decline is believed to result from the stresses of a changing climate, often combined with several successive years of insect defoliation. In some cases, where soils are naturally poor in base cations and therefore “acid-sensitve” (as at Hubbard Brook), acid rain may also play a role in sugar maple decline by further stripping the soil of important nutrients. Weakened by multiple stresses, sugar maples become more susceptible to pathogens. Three fungi that commonly attack sugar maple are Armillaria mellea (root rot), Nectria cinnabarina (branch canker) and Steganosporium ovatum (twig blight). It is the activity of these secondary pathogens on an already weakened tree that eventually leads to the death of the tree. Sugar maple decline is apparent in some areas of the Hubbard Brook forest, however it is not yet a widespread problem here.
Sugar maple decline links: