Q.How to control worms on flowering kale?
Each year I develop small worms on my flowering kale. I have been told to use tristar incesticide…..your suggestions? Thank you.

Neem Oil is a good treatment. Use it throughout the growing season.
In severe cases Bt or Bacillus thuringiensis is a good choice.
Here are some links for you.
https://www.gardeningknowhow.com/plant-problems/pests/insects/prevent-caterpillars.htm
https://www.gardeningknowhow.com/edible/vegetables/kale/kale-plant-protection.htm