Spider mites across my yard
After thinking I had spiders, i did some research and it appears I have spider mites as well as spiders. Questions: I have a 16x16 yard on capital hill what is the best way to treat? (Seems to big for a spray bottle). I have 3 lovely garden spiders - will they be harmed? Plants impacted are boxwood, Manhattan eyonomous, hydrangea, with webs, but my lavender and peony seem to be dying ( see photos attached) - Is this related to spider mites? Finally, my honey locust tree and two other shrubs don't appear to be impacted - do they need treatment as well or will they be negatively impacted?
Our recommendation is not to treat anything.
Your photos do not show any noticeable signs of spider mites, which would include leaf stippling (yellow dots) and impossibly fine webbing at the leaf nodes. Spider mites are as small as the period on a page, and to look for them you bend a branch over a sheet of white paper and sharply tap the branch and watch for tiny specks walking across the paper.
We think your plants (other than the lavendar) look pretty good for this time of year. Peonies often end up with powdery mildew and get unsightly in our area this late in the season. As long as there is still some green tissue, they are storing sugars into their roots for winter.
It is highly, highly likely that you have more than 3 beneficial spiders in your garden, and that is likely the webbing you are noticing. They are all good guys...beneficials which help control other problems-pests in our gardens.
Treating with chemicals is always a last resort and usually not necessary, as we manage problems as organically as possible. Chemical treatments often do wipe out all insect life, and that's not a healthy garden at all.
Here is our page on Spiders: https://extension.umd.edu/hgic/insects/predatory-spiders
Lavender likes full sun and a well-draining area. In our area, good drainage is paramount for survival. It may be time to plant new ones in the spring.
Thank you for your guidance. Will do and glad to know most of it is healthy!