Question
Hi - I have two weeping willow trees about 4 years old maybe 18 to 20 ft tall, one started dropping leaves like crazy found out after some investigation it had borers.  Pulled out one was white with brown head larva, looked like willow borers, sprayed weekly for 6 weeks and put plugs in the base of the tree it continued to dropleaves one large trunk kept leaning over further til it was touching the ground so I cut that off and put the black tar looking bandage stuff on it after I cut if off. One tree is healthy with minor damage seems insecticides possibly worked other looks like it's dying do we need to cut it down.  I could email photos. I was hoping it would recover but it doesn't appear so, please advise.

Answer
If the tree still has green foliage I would try treating the trees with an insecticide called Bayer Advanced Tree and Shrub Insect Control. This is applied to the soil around the tree and the roots carry the insecticide to the trunk and branches and when a borer enters the tree it is killed. This will prevent borer attack for the season. Here is a web link to this product--check with your local garden type store for it.

IF there is little green left on the tree you might as well remove it. But if there is green I would try to save what you can.  

http://www.bayeradvanced.com/tree-shrub-care/products/12-month-tree-shrub-insect