As you're in MA, sounds like Winter Moth, which has become a major pest in the last few years. The worst part of them as a pest is that they seem to prefer flower buds, so they can really decimate a crop.

http://www.umassgreeninfo.org/fact_sheets/defoliators/wm_id_man.html

This is the first time I've been fairly aggressive with them and it's been working pretty well. A couple sprays with BT early on helped keep the population down and as soon as petal fall occurred, a follow-up with Triazacide and another 7 days later seems to have done the trick.

Dormant spray isn't very effective as you noticed the threads. When they hatch, if they don't find any food on their host trees, they spin a thread and ride the wind until they do. I had a lot of trouble getting some new cherry trees established last year because of this.

They seem particularly fond of apples, plums, tart cherries, blueberries and pears. Sweet cherries they don't seem to like as much and they haven't bothered my peaches, hardy kiwi, figs, raspberries or paw paw.

Thank you so much for the advice. I am new to the world of pesticides. Is it worth spraying the tree now or is the tree just shot for the year (there are not many leaves left) and I should start with the BT early next year? Do you spray all the trees (we have one apricot but also 10 apples, a peach, and something else that seems like a fruit tree but does not produce anything, this one has lost about 1/3 of its leaves). I assume they would all need to be done since the caterpillars can fly on their strings? As an aside, you can grow kiwis in MA, that is interesting.
Thanks again!!