Hello,

As you are probably aware, there are a lot of Box Tree Moth outbreaks in Oakland County. You are doing the right thing to look for these pests inside the plants. Unfortunately, it is hard to tell if the webbing is from these insects or others unless you see the pests in some stage of life. However, from your photos I do not see any caterpillars. It would be good to keep an eye on these webs and check for the presence of box tree moth caterpillar larvae (larva looks like a very small caterpillar, greenish yellow in color with a shiny black head).

Here is a link to an article on Box Tree Moth for Michigan homeowners:

What the box tree moth quarantine means for Michigan homeowners - Floriculture & Greenhouse Crop Production (msu.edu)

As with most pests, timing and the life cycle of the insect, are critical when treating them. The above article does discuss the use of Bt but note the following regarding Bt vs BtK:

"However, Bacillus thuringiensis is not an effective control for larger caterpillars, eggs or adults. Bt is a bacterium that kills insects when ingested. There are subspecies of Bt that affect specific types of insects; kurstaki is the subspecies that specifically target caterpillar larvae. Look for product labels that say Bacillus thuringiensis subsp. kurstaki (Btk)."

Be sure to follow all specific application information on any product you may be using.

Additionally, here is a link to MSU's Box Tree Moth resource page for other articles and more info:

Box Tree Moth - Box Tree Moth (msu.edu)