You might get more responses on the 'Trees' forum.

I would not worry about it and don't bother trying to apply any treatment. Tulip trees are first in my area to get discolorations and drop as the heat of summer progresses. I'm surprised you don't have more yellow leaves in that picture.

Most tulip poplars in the south look kinda rough by September. The drought doesn't help.

I wouldn't treat this or any other tree or shrub ailment unless the tree seems to be losing vigor or not rowing from one year to the next. It is common for the leaves of many plants to be somewhat chewed up, blighted, yellow, etc. by the end of the summer, but as long as the plant is growing and vigourous each spring, all of the obvious problems aren't really harming the tree. For example, it is normal for almost all of the milkweed species here to lose most of their leaves to caterpillars each summer. Right now most of them look like skeletons. however, each spring they sprout vigorously, spread, flower and set seeds. The caterpillars certainly don't help the plant grow, but they also don't do much, if any, harm. Same is probably true of the things on the leaves of your tree.

This looks REAL familiar to me. Look at those tulip tree leaves, and any leaves of plants, small trees, etc. under or near them. If the leaves feel sticky at all, something called honeydew, you have tulip tree scale. VERY Bad! This will spread to all under or nearby plants and kill them. I lost a beautiful, old plum tree, planted near my neighbor's 60 foot tulip tree, last year. It's very common here in VA. If sticky, take your hose and very thoroughly wash all leaves, including under plantings, anywhere near your tulip tree. and throw away any tulip tree debris that have fallen. Then you must spray everything with insecticidal soap. In the EARLY spring before new leaves, you have to spray the tulip tree with horticultural oil, even if the tulip tree is very tall. Read the label for control of scale. Hope this is not actually your problem! What a huge headache last year for us. By the way, the under plantings survived beautifully just being well washed and srayed with the insecticidal soap.

i dont think you got no problems here. this is just bugs and nature doing what they do best.