I don't know what spraying open flowers will do. I spray early in the year when there are buds only and then I spray about two weeks later to break the cycle. I spay in the evening when the bees are done if there are open flowers. By the next day, those flowers are gone. And the buds sprayed day before open but that doesn't seem to harm the bees. Never had a hummingbird interested in any daylily. So I would suggest not spraying in the morning or daytime when bees might be visiting.
I have always used Bonide (brand name) Systemic Insect Control.
