My Zenia's don't like sevin that I used for insects? Why?

I save the flower tops (seeds) and resow my zenia bed each year. Last week there were numerous insects about the yard, garden, and flower beds (lots of beetles). I mixed some Sevin and sprayed numerous varieties of plants. Today the zenias (now about 24" tall) are wilted as if they were sprayed by plant killer. All other plants look fine. What's up?