I have a sweetgum tree which gets webworms each year. That causes an appearance similar to what you described. It was the worst ever in 2007--the rainy year. This spring I put out trichogramma wasps twice. We still got a significant amount this year, but it hasn't ruined the apperance of the tree this time. One of these days I will get around to getting one of those trombone sprayers so I can kill the ones that the wasps don't take care of with orange oil.
My sweetgum tree was purchased before we started hearing Howard talk about circling and girdling roots. We also heard him say that they prefer deeper and more acidic soil than what we have in North Texas. We also realized that it was planted too deep with no root flare. So one winter, after it had been in the ground maybe 2 years, still a small tree (unfortunately purchased from a big-box store), we dug it up, raised the level of soil in the ground, and replanted it. However, it had a huge girdling root that we couldn't really do anything about. It seems to be strangling itself. DH did not want to call out a tree service for a $20 tree and we don't have the equipment or know-how, so we just let it be, while raising the tree so it has more soil under it. It has done better since then, but always gets these webworms in the fall, probably because it's not completely healthy. It never has developed a root flare, years later, I guess because that girdling root keeps it from growing that way.
I grew up in St. Louis in a tract-home neighborhood and the builders put sweet-gum trees in everyone's lot--one in front and one in the backyard. They do great in that area and get huge--we spent entire summers climbing them--and sometimes throwing sticker balls at unsuspecting passers-by! (Mean, I know!) And the fall color cannot be beat. I was trying to bring some of my childhood tree-love to Texas, but the sweetgums do not get nearly as large or wide as they do in the midwest. Still love em, though.