If you spray them in the evening, after the sun is off of them and the bees have gone to bed, the heat shouldn't be an issue.

Butterflies and bees love zinnias, so please don't use Seven!

There are some natural products made from herb oils that you can spray on the leaves (not the blooms) that aren't so toxic. I think Garden Safe may be one of the brands.

Cameron

Have only used Seven dust a couple times and that was years ago, just thought it would be easier on the foliage; didn't think about the butterflies and bees, they could still land on the leaves and carry the poison. Well, I'll probably not do a thing as usual. Like I said, there's only a bit of ragged foliage not much.

You can always get out the blender and mix some fresh garlic, onion, hot pepper flakes, milk and a bit cooking oil and whiz it all up with water. Filter it through a coffee filter and spray it on your zinnias. Often times IME this is enough to make a plant unpalatable to whatever has been eating it. Many insects are pretty specific in what they like to eat, and changing its smell will be enough to discourage the munchers.

Alternatively, I find that a wander out into the garden at dusk or early in the morning with my coffee will allow me to catch the critters responsible. Since it's cooler, the bugs are slower. I drop them into a container of soapy water to kill them, and this is enough to keep the damage to a minimum.