Hello John, happy to help.

You may have spider mites in your arborvitae. Shake the twigs where there is a web over a sheet of white paper (hold as flat as possible.) You may see tiny brown or reddish specks on the paper.  Hold it still and watch to see if they move by themselves. That would indicate spider mites. They're almost impossible to see on the web with the dark foliage in the background. If you think they are spider mites, here is a link to more information about what to do.

Spider mites like dry weather and we've had a very dry season this summer. If you've been watering diligently at the soil level, the external foliage has been dealing with few rains and relatively less humidity this summer - a perfect environment for spider mites.

Your shrub has experienced pretty extensive damage. Check your other shrubs with the white sheet of paper to be sure. If they have it, I recommend asking the nursery where you bought them if there's a return policy due to perhaps bringing the mites with the plants to your garden. But also know that they do come in on the wind which is why it's pretty important to treat for them before they spread to your other shrubs.

Recent DNR and newer U of MN (but not yet publicly disseminated) research has been trickling out about the use of neo-nic products as being harmful to beneficial insects and animals. The link I provided offers non-chemical and biological options to try before opting for chemical solutions. I encourage you to try those first. If you should decide on chemical option, be sure to read the product label to ensure it is intended for spider mites and always follow the directions for how much and when to apply - more is never better.

Good-luck!