There are several possible culprits, and the odds are they are working in combination to produce the browned foliage and tip dieback your photo shows. For a start, notes Alan Watson, director of The Arboretum at the University of Guelph, in a very dry period such as you experienced last summer, it's likely many of the trees' small rootlets would die. Much of the effect on the tree would be delayed until the following year when (no matter how generous the rainfall) the trees, with their reduced root capacity, would have difficulty taking up enough water and nutrients to thrive.

Additionally, for the past six years or so, Ontario has been experiencing outbreaks of larch casebearer (Coleophora laricella). Most of the damage occurs in late April and early May when the larvae feed on the needles, causing defoliation that, if extensive, can seriously weaken the tree. In turn, the tree becomes vulnerable to attack by another pest of tamarack, the larch beetle (Dendroctonus simplex).

If you're feeling that nature is ganging up unfairly on your tamaracks, take heart - the trees normally recover from a casebearer attack by putting out a fresh set of leaves. And after examining the photo you sent, Dan Rowlinson, a forest health technician with the Forest Research Institute in Sault Ste. Marie, speculated that this tree, at least, looks likely to survive.