It is important to have the Bt stick to the leaf because it must be eaten to be effective. Cabbages and their relatives have very waxy leaves that repel water.

The easiest thing to try is spraying less so that the droplets stay small and don't run off. Just apply a fine mist. This is easier to do if you have a pump-up sprayer that can create a fine mist. If you are spraying with one of the hand-held quart size sprayers, this may not work.

There are commercial spreader/stickers that are very good at making the liquid stick to the leaf and you can add these to your spray mixture. These are the most effective. You can also try adding a little dish soap to the mix to make it spread out. This might help, but again, it is important that you not apply so much that it runs off.

I don't believe insecticidal soap is all that effective on loopers, especially larger ones.

Thank you. It's the liquid concentrate Bt and I use a gallon pump sprayer. It's hard even getting the mist to stay...just a little breeze make it roll off.
I will get some non-detergent soap and add a few drops.
I was wondering if insecticidal soap would help me ward off SVB? I noticed a hole in one of the zucchini flowers and thought the soap might be helpful. I wanted to make my own but I don't know the recipe.
Is it just soap and water or is there some other ingredient?
Thanks. J

Insecticidal soap works best on soft-bodied insects. If the B in SVB stands for beetle, then the soap would be pretty ineffective.

Both the insecticidal soap and the home-made version are mixed at 1-2% solution. That would be 1.25 - 2.5 Tbsp./gallon.

Insecticidal soaps of about 1 percent solution are most effective. Mix 1 teaspoon of real soap with 1 quart of water to make an effective homemade version.

SVB = squash vine borer