LIndane is very toxic
and it is good that it is off the market. The normal organic recommendation would be to spray beneficial nematodes onto the tree so they can get in the borer holes and prey on the borers. Then the sick tree treatment (available on this website) to boost your tree's health because borers normally only attack a tree that is in stress. I have used this method to great effect in the past. Another option that is only recently available is to use a spray product called Bioganic. It is available at most Lowe's stores in Texas and several of the independent stores too. You'll want to get the hose-end version as it can be sprayed pretty high in the tree. It's made from plant oils and blocks nerve receptors that are present only in insects so it's safe for your family, pets, birds, etc. but it will knock out the insects. Hope this is helpful. 