Hello Olga
The first picture shows feeding damage by caterpillars. Look at the undersides of leaves to see if you can find any. Many caterpillar types could have done the damage, and they may be done for the year. Or, there may still be some around- if you can get pictures of caterpillars on the tree, we may be able to identify them.

The last pictures show possible damage by aphids, tuliptree aphid being a possibility. Check the underside of leaves for these.
https://entomology.ces.ncsu.edu/2020/05/tulip-tree-aphids-and-scales-feeding-and-dropping-honeydew/


Check your branches and twigs for tuliptree scale. See pictures here to know what to look for—
https://edis.ifas.ufl.edu/publication/IN1150
https://extension.umd.edu/resource/soft-scales-trees-and-shrubs


If you find scale insects, please send clear pictures so we can confirm identification.
Scale and aphids typically leave a sticky substance on leaves and twigs. Heavy feeding can cause the off color leaves.
Once a particular pest is confirmed as present, we can recommend treatment options.

In the meantime, keep the tree watered during the hot weather this summer. Adequate moisture helps the tree recover from the damaged leaves.

Laura, thank you for your reply to me about my tulip tree. I watched the tree carefully. There no caterpillars and no scale problem. I did saw three different bugs on it during the day. Please see them on the images below. My guess is that one on those species is the cause of the problem. I am also guessing it is the biggest beetle on the first image. It did look like it was eating a leaf. 

Thank you, Olga, for the additional pictures. Thr iridescent beetle is Japanese beetle- here are details and control information—
https://extension.umn.edu/yard-and-garden-insects/japanese-beetles

I am not sure which beetle you have with the black and yellow stripes; it may be striped cucumber beetle-
https://extension.umaine.edu/ipm/ipddl/publications/5038e/

White flies out doors are not usually a problem. He tiny white insect in your picture looks like something else. I am asking our MSU Entomologist to look at your pictures and identify them.

Hello Olga,

I think the feeding injury happened before the Japanese beetles showed up.  They just emerged from the soil a week or so ago and the damage to the leaves appears older than that.  My first guess would be spongy moth caterpillars.

The other photos show a striped leaf beetle, a lady beetle and a small moth. I'm not sure what the brownish smears are; they do not look like anything bug related.  I don't thin any of these are cause for concern.

For homeowners, recommended products for controlling insect pests on ornamentals are cyfluthrin (sold as BioAdvanced Vegetable and Garden Insect Spray, Insecticide), bifenthrin (sold as Ortho Bug B Gon) and carbaryl (sold as Sevin). Be kind to our pollinators by spraying in the evening and avoid spraying blossoms. Be sure to read and follow all instructions on the label before using any pesticide.

Best regards,

Howard