kill insects on vegetable plants
You can sprinkle with diatomaceous earth. It kills many pests in the garden. This article tells how to apply it. https://littlesproutslearning.co/how-to-fight-slugs-naturally-with-diatomaceous-earth-and-a-giveaway/
A botanist I follow recommends using Dr Bronners to make a soap spray. A few squirts of Dr Bronners castile soap in a spray bottle of water. Spray on the underside of the leaves.
I have also hear coffee grounds sprinkled around the plant on the soil helps.