Thank you for the question. It is important to determine the cause of your tree problem before attempting any treatment to avoid unnecessary use of systemic pesticides like those you mentioned that may cause collateral damage to beneficial non target insects such as honeybees and bumblebees.  We can't tell if the holes you describe are from a borer insect, sapsucker, or woodpecker. Borers generally attack trees that are distressed for some reason and sapsuckers or woodpeckers may create holes in trees to get at insects and/or tree sap but the birds rarely cause tree problems such as loss of leaves and branch die off. You might have a borer problem or not but it sounds like this tree is in distress and is important in your landscape. The best idea is to have a certified arborist come evaluate and definitively diagnose the problem and give you some treatment options. Search for reputable arborists in your area here: http://www.isa-arbor.com/ 

Read more about borers here: http://www.ext.colostate.edu/pubs/insect/05530.html

Read about sapsucker damage and view the characteristic pattern of their holes here: http://www.clemson.edu/extension/hgic/tyk/2008/tyk01.html 

This publication from the University of Minnesota may help you self diagnose your tree problem: http://www.extension.umn.edu/garden/diagnose/plant/

Thank you for contacting Extension.