CULT: Merit grub control/imidacloprid

Hi folks!

This morning I extracted a 1" long iris borer (in tact and uninjured) from a rhizome and sent him swimming in a solution of imidacloprid (active ingredient of Merit) at the rate of 1 drop per ounce of water. Within a half hour, he was dead. That of course raises the question of whether the imidacloprid killed him of it he simply drowned. In the Mallorn archives there are accounts of soaking borer infested rhizomes over night in bleach solutions of various strengths and having the borers survive. Has anyone ever seen a borer *outside* of a rhizome survive under water over night? I wonder if, when they hide in their tunnels within the rhizomes, there aren't air pockets big enough to sustain them even though the rhizomes are submerged. I'd really like to know if a borer can hold its breath under water over night so I might have a better idea about what killed the victim of my diabolical experiment. If nobody knows, I guess I'll just have to find another one of the same size and send him swimming in plain water. Unfortunately that won't be too hard to do this year. Due to health problems, I didn't get one of my (fortunately isolated) iris beds cleaned up last fall and it's a borer smorgasbord this summer.

Janet in Denmark, WI
zone 3/4
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