Tulip tree losing its leaves now

I have a very large Tulip tree which is already losing its leaves. The leaves on the tree are all brown / yellow with a bit of green remaining. All my other trees are still green. I looked at photos of the tree same time last year and it was all green. Could it have an infection?

I think it is from insect damage and the drought like conditions (at least here in Indiana.)

I also have a large Tulip tree which is losing some leaves. I've seen some trees in town which were almost bare.

http://www.ppdl.purdue.edu/ppdl/hot12/5-23.html

I'm hoping it's insect damage. I have bought some treatment from the Nursery. I don't have the sticky problem though. Let's see how it goes.
Thanks.