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Re: CULT: Merit grub control/imidacloprid

I appreciate all the comments on the borer problems. Thank heaven I only have only one isolated iris bed that got infested this spring! I've been digging that bed all week.

After attempting to drown a borer in plain water, I'm pretty well convinced that they have very minimal oxygen requirements in their larval stage. I completely submerged a 1" long borer in water and after 27 hours was convinced it had drowned. I hauled its limp and lifeless form from its swimming pool and put it in a plastic container. I turned it on its back and watched it off and on for the next 6 hours then covered the container and walked away, certain it was dead. The next morning the darned thing was up and crawling around! Yikes! So even though imidacloprid is not listed as a contact poison, it appears to work that way to some degree, since the first victim did actually die after 1/2 hour of swimming in the imidacloprid solution.

Perhaps the only practical knowledge I've gained from this is that I *may* be doing some good by soaking borer infested rhizomes in a solution of liquid imidacloprid when the borers are so small that I can't find and extract them with my tweezers. It's late enough in the season now that most of the borers have already done their dirty work and are underground pupating, so soaking the rhizomes in imidacloprid at this stage is useless, unless I happen to nail some late hatchlings. Now the rhizome soaking is more damage control and involves bleach instead.

I bought my propane burner for burning off foliage this fall and I bought my bag of Bayer Advanced Grub Control for next spring. I'll be ready for the beasts next year!

Janet in Denmark, WI
zone 3/4

I hope you will keep experimenting. Good time to do so, I'd think, albeit

I think water can almost certainly flow into those hollowed out rhizomes
while in the soil, too, during a saturating rain. Hence the talk of rot being a
consequence of borer activity.

And I think we have established here that borer can be fully active in
aquatic irises with submerged rhizomes....someone will please kindly correct me if
I misremember. Apropos, it is believed that the native host is Iris
versicolor, a beardless species with wetland preferences. There could be a seasonal
aspect of this, I suppose.... wet areas drying to damp about the time of

Wonder how those larvae actually breathe.
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