Twin mature Sugar Maples

(Question)

Hello. We live in Waubaushene which is 50 kms north of Barrie and Zone 4/5, trees 80 ft tall and 2 ft diameter growing side by side on the edge of our woodland with Basswood, Birch, Cedar, Ash. For the last few years there has been early leaf loss and dieback of individual lower limbs. But the most significant thing is the leaves at the outside range of the canopy are “cupped” in an upward fashion. There are other younger Sugar maples without these conditions.Any ideas as to the cause or remedies ? Thank you in advance.

(Answer)

There are several diseases and pests which may cause problems for your Acer saccharum, or Sugar Maple.  The symptoms you describe are consistent with a few different ones.  Browned and cupped leaves at the edge of the canopy can be caused by leaf scorch during periods of drought in which inadequate soil moisture results in less water reaching the leaf tips and margins.  The fungal disease Anthracnose can cause cupping and browning of leaves along and between the veins and extending out towards the tips – these symptoms are often confused with leaves showing symptoms of scorch.  During wet seasons, infection with Anthracnose can often cause partial defoliation of trees.  The Maple Petiole Borer (a non-stinging wasp commonly called a sawfly), which attacks all maple species, but particularly Sugar Maples, can cause leaf drop during the early part of the summer – this is unsightly, but will not cause any lasting damage.

It is also possible that your tree is showing symptoms of what is generally termed “decline”, which describes gradual and progressive death of branches generally starting at the tips and occasionally beginning with the lower limbs (although it is more usually associated with dieback at the crown of the tree).   Early leaf drop is also associated with this condition.  There are many complex factors involved in decline and dieback, as well as in the diagnosis of any of these conditions, and it is always wise to seek out a certified arborist for an on-site consultation. You can find an arborist near you through the International Society of Arboriculture (ISA) website: https://www.isa-arbor.com/faca/findArborist.aspx