For a number of years now I have grown one or another variety of Garden Sage in the ground, or in large pots. It has always grown vigorously and without much trouble. This year I started two pots, which until a week or so ago grew vigorously and seemed quite healthy. Now they are almost entirely defoliated, and covered mostly from underneath by silken webs. The leaves are eaten full of holes from underneath, until they are completely destroyed. I can provide photographs if that would help. When you turn over a leaf you find numerous slender, half-inch-long caterpillars that move quickly out of view. The plants are now - barely a week after the first obvious small round holes appeared in the leaves - almost completely destroyed.
I haven't seen this before, at least not on anything like the present scale. We are having extremely hot and dry weather - daytime temperatures up to and beyond 110 F., and relative humidity as low as 0% (really). Combine that with strong winds and it's hard to keep container plants alive - if not watered copiously in the early morning they would be wilted to the point of collapse by noon. Apart from the sage plants I have several kinds of hot peppers, and four tarragon plants I bought this Spring to replace ones I had had for several years but lost this last winter. Everything else is (given sufficient water) thriving, but the sage plants are an utter disaster. Before dousing the plants with insecticide (I generally prefer not even to have such things in my house) I am curious to know what beast this is, and also perhaps how to deal with it. I'd like to salvage the plants if possible, since it's effectively impossible to obtain replacements here until cooler weather arrives in October or November.
For pepper enthusiasts - I have Thai culinary, pequin, Caribbean red, and one Bhut Jolokia plant. And yes, I use them in cooking, that's indeed why I have them.