Regarding your webpage about pickleworms, the last sentence in the article says that Bacillus thuringiensis won't work once the caterpillars are inside the plant tissues, it’s too late for treatment, so spray early and spray often. But I've read that BT is systemic, so won't it kill the bugs even if they are inside? https://www.gardeningknowhow.com/edible/vegetables/cucumber/treating-pickleworms.htm
Certified GKH Gardening Expert
This fact sheet from the National Pesticide Information Center mentions that different types of Bt are engineered to affect different types of insects. The kind of Bt that is effective on pickleworms targets the larvae. Because pickleworms lay their eggs directly on the foliage of a plant, it's important to spray the Bt "early and often" as the article says, so that the pesticide can kill the larvae BEFORE they mature enough to tunnel into the flowers, vines and fruits.
You may also find this fact sheet on pickleworms from the University of Tennessee helpful: