Done a stupid thing Blackfly

I've never heard of it either Jalima but its crawling with Blackfly and of course the Ants have joined in.. If I could get to the garden shed I'd of checked the bottle by now but every time I go to venture out down comes the blasted rain again.

I would think it depends on the type of bug spray and its contents. Some are "biological."
There's another kind of blackfly around here today, and they're driving me mad. They get in your hair and all over - not going out again.

Read instructions and phone or e-mail manufacturers if not absolutely sure. In doubt- I wouldn't chance it.

Blackfly on rhubarb?

I have never checked. Would probably just have washed it with a very dilute solution of Fairy Liquid.

oh why didn't I think of that, thanks GandTea

Read the instructions, they should say how long you have to wait before harvesting.