Hello and thank you for contacting Ask Extension. Unfortunately there are several insect, disease, and environmental problems that affect boxwood. Here is a link to a great document that includes some really good pictures that can help you identify what your problem/problems are.

https://www.canr.msu.edu/resources/whats-wrong-with-my-boxwood-common-issues-and-solutions

Based on what I can see in your pictures I think your problem might be boxwood mites because of the stippling (yellow spots on leaves). The boxwood mite, Eurytetranychus buxi, is a spider mite that feeds on the undersides of leaves and is difficult to see even with a hand lens. Infested leaves appear to be pin pricked or stippled with tiny white or yellow marks. Applying high nitrogen fertilizers may lead to higher numbers of this mite. Like most other spider mites that plague Michigan landscapes, the boxwood mite overwinters as eggs on the undersides of leaves. These eggs are greenish, round and flat-topped. They generally hatch in May and complete a generation in two to three weeks. Since multiple generations occur each year, it is important to apply control measures early in the season on plants that show high levels of the mite feeding injury. You can try spraying water on the leaves to wash off the mites or spray with summer rates of horticultural oil or insecticidal soap. Make sure you follow the instructions on the label.

There could also be some winter damage present. Signs of winter damage include: browning of foliage and spring leaf drop. Damage can be caused by cold, wind, sun, and salt or a combination of any of these. Severe or repeated damage can eventually kill plants. Environmental stressors like salt damage and drought stress can also cause browning in boxwoods. Salt spray from roads or sidewalks can desiccate foliage, especially on the side facing the salt source, while salt buildup in soil can interfere with water uptake. Drought stress is most common in newly planted boxwoods or during extended dry periods and typically shows as browning in the center of leaves and yellowing foliage. To lessen the effects of winter damage make sure you plant hardy cultivars, avoid late-summer pruning, and use burlap screens or windbreaks for protection.

I do see some webbing present but I don’t see the typical skeletonizing of the leaves so I don’t think it is box tree moth, but you should look for the green caterpillars that have black stripes and a black head (they are often present this time of year). Box tree moth is an invasive pest in Michigan that can defoliate and kill boxwood shrubs. Your help in spotting and reporting this pest is critical, especially in areas outside the current quarantine zone. Since first being detected in Michigan in 2022, box tree moth has spread and established itself in a 13-county area in southeastern and central Michigan (Livingston county is included in this quarantine zone).

If you want a definite diagnosis for what your problem is, you can send your pictures to the Plant and Pest Diagnostic lab at Michigan State University. Their email address is <personal data hidden> Include a close up of the leaves and stems as well as a picture from a distance. Here is a link to the Plant and Pest Diagnostic lab’s website https://www.canr.msu.edu/pestid/

Here are some additional publications about boxwood problems.

https://www.canr.msu.edu/news/boxwood_insect_pests

What’s wrong with my boxwood? Boxwood pests and other threats - Floriculture & Greenhouse Crop Production

Browning of boxwood: Is it boxwood blight? - Landscaping

How to take pictures of your boxwood for the MSU Plant and Pest Diagnostic lab.

Boxwood - Plant & Pest Diagnostics