Found these tiny white barrel-shaped things neatly lined up on the underside of a leaf. They look like a microscopic drum set. Should I be worried?

easiest method is manual removal. Wear gardening gloves or use a piece of tape, a butter knife, plant label, or even your thumbnail to scrape the egg mass off the leaf. Drop it into a small container of soapy water. A mix of about 1 teaspoon of dish soap in 2 cups of water is enough to finish the job.

You can also snip off a heavily infested leaf if the plant can spare it. For a larger plant, I keep a jar in my garden tote specifically for pest