Theoretical Iris Borer Questions:

If one were to plant a new iris in a container with potting soil, and then cover the container with a fine woven net tent in the fall when the borer moths lay their eggs,
would this pretty much guarantee a borer free plant?

If one were to dig and discard all irises in a country yard (no near neighbors)
how long would it take for the ground to become borer free? One year?

If one were to replant the clean iris in the borer-vacated ground, and cover with a tunnel of fine net, (like the plastic ones they use for starting early crops) when the moths are about to fly, would this keep them off of the plants?

I was just about to buy some "Merit" for my borer problems this spring when I read several articles about "disappearing bees" - no one knows what is causing this. I was also put off by the big bags of grub control stacked at walmart - it looks like this stuff is being poured onto lawns. Anyways, I want to keep my garden a tiny little outpost for chemical free growth.... Don't know if I should just pitch out all the irises or try some different approaches.
Sharon

Sharon, I don't know the answers to your questions, but I do know that you can reduce borer populations substantially without chemicals by maintaining a very clean garden, esp. in late summer-fall when borer moths are laying eggs. If the moths can't find any dead or dying leaves or other suitable garden debris on which to lay their eggs, they'll go elsewhere. Also, doing a very thorough garden cleanup in early winter and/or early spring before temps warm up to 70 degrees, and cutting off and discarding (trash or burn, NOT compost) all of the previous year's iris foliage will remove most of the borer eggs before they have a chance to hatch. Lastly, go through your irises once a week throughout the spring and pinch each leaf thoroughly from bottom to top to squish any feeding borers before they can reach the rhizomes.

If you do those steps, you should be able to minimize borer activity in your garden.

Laurie

Hmmm....Pinch each leaf, eh? That's an idea.
I thought I had done a good cleanup this spring, but evidently I missed some because I saw dead leaves (short) with tiny red egg clusters near the top and I could see the gooey slime in the mid-leaf of each of those plants. It seems like they travel down the leaf pretty fast, and then the bottom of the leaves are hard to squish.

My best friend has gotten iris borers.. and she mulches.. Would it be better if she didn't mulch?

It is normally advised not to mulch bearded irises, esp in a climate as humid as MO. Mulch retains too much soil moisture around the rhizomes which can cause bearded irises to rot.

This is what I am doing at present:

"Iris plants should be carefully watched during the summer months.
If there is any evidence that borers are at work, the plants should be dug up, the borers removed and destroyed, and the rhizomes carefully cleaned before being reset." (sorry, don't remember where I found this advice. Somewhere at google.)

There is too much "evidence" to my newly trained eyes, and I am digging them now rather than wait till the end of summer as I did last year. Too big of a job then.

I am treating this as a little independent research study. Whether or not I will ever be able to grow irises en mass is yet to be discovered.
Sharon

As an experiment, I am digging and doctoring as described in the last post, then I will replant in boughten potting soil in long window box containers that will be placed in front of a window in the garage where they will remain all winter.

Has anyone tried growing irises in containers?

Is there a certain temperature they need to have in the winter to complete their cycle? I know they grow in warmer climates than Iowa (Washington, Oregon) so would a winter in a garage hurt them?

I personally think that's a bad idea, but if you're only doing it as an experiment with rhizomes you can afford to lose, then no real harm done.

First, the irises will not be able to receive adequate light through a window. Second, the heat from both the garage itself and the light through the window may trigger off-season growth that may not be beneficial to the bloom cycle of the plants. Third, if your garage is not heated, the rhizomes will be subjected to much greater temp fluctuations and repeated freeze-thaw cycles in the window boxes that will almost certainly kill them.

But like I said, if you're using extra rzs that you can afford to lose, go ahead and experiment. You never know, I might be wrong about everything I just wrote!

Laurie

You may find that some of the tough ol' heirlooms will survive the unheated garage method better. You could put them inside a closed larger box insulated with newspaper, styrofoam, etc. When you open that garage door at 25 below, things can get pretty cold!

I am now thinking I will try something else - row covers with something like mosquito net for the choicer plants when the moths start to fly. If the area around these rows is kept clean, and the moths can't lay their eggs on or near the irises, no borers on those plants, right? I have also heard recommendations to sift your soil where you are replanting to make sure you haven't left some borers or pupa in the soil. I am trying to dig them earlier this year so they don't have a chance to "go to ground" first. A new plot of ground ( at least 1-2 years between iris plantings?) would eliminate the need to sift the soil.
Maybe I can get a grant or something to study the fascinating borer!

I think there is so much that we don't know about the borer, and there probably has not been alot of research/or experimentation done on them.
Like, why is it they don't survive in the West part of the country?
I have had horrendous borer infestation this year and I attribute it to the fact I could not apply my Merit until May. Too late!
No one has mentioned burning off the borer eggs in Spring.
I have not tried this, but those who have say it works.
Laetitia