Shrinkrap, I’ve used Bt to control squash stem borer, tomato hornworm and an excess of Black Swallowtail caterpillars on Fennel and Dill. It also works on Cabbage “worms”, a butterfly larvae. Since many Brassicas, like Collards, are hard to wet, using the dust is often more effective. The dust can come in handy for unusual applications:
We used to have a 50 foot tall wild Black Cherry tree, Prunus serotina, which got defoliated annually by Tent Caterpillars. Starving, the caterpillars migrated into the nursery and were attacking Pitcher Plants, Sarracenia. There was no way to spray the treetop, so I got some Dipel Dust and made golfball-sized Dipel dust balls out of newspaper. Using a slingshot, the balls exploded when they hit a branch, releasing the dust all through the canopy. It wasn’t long before it was raining caterpillars, disgusting! Worked like a charm.
