I did everything everybody said last year about the iris borers (which at that time were SMALL little guys that seemed to die when the rhizomes were soaked in the bleach water)...
And this is the result! WARNING: these pictures are some of them gross depictions of dead borers. View with discretion.
This message was edited Jul 28, 2005 10:33 PM
This dad gum feller and his family before I massacred them...
here is his picture
and his whole famn damily
man did those chomped iris rhizomes STINK!!!! Thank God I had my beautiful Stargazer Lilies to soothe me as I chopped and dug and wept in my heart ...
This is me with the stargazers, rudebeckia, bergamott, zebra grass, daylilies, yellow loose strife, black eyed susan, daisies and echinacea purpurea in the background... He caught me chopping the darn borers apart with my trowel... LOL.
Eeewwww! Did you apply Merit early this spring just as your irises were breaking dormancy and beginning active growth?
laurie, I never heard of Merit.
What is it, where could I get it, and how is it applied?
Merit is a systemic insecticide that is taken up by the plant and kills newly hatched borer larvae as they begin to feed on iris leaves. It's active ingredient is imidacloprid, manufactured by Bayer. It's the same ingredient used in Advantage pet flea control products, so it's comparatively safe for wildlife, companion animals, and the environment (moreso than other systemic insecticides, anyway). It also happens to be very effective against borer larvae if applied early in the spring. Timing is everything, though, since borers are no longer susceptible to systemic insecticides once they've been feeding a while and grown larger.
The ingredient Merit is marketed in several products, strengths, and forms (granules and liquid). The one I use that has been remarkably effective for me is a granular form named Bayer Advanced Lawn Season-Long Grub Control. I order it through my local farm feed store, but it should be available at larger garden centers. Whatever you buy, make sure it contains exclusively Merit (or imidacloprid) as the active ingredient. You don't want it combined with other insecticides or fertilizers.
I sprinkle 1/2-1 tsp over and around each iris clump in early spring just as irises are beginning active growth. It's best to scratch it into the soil surface a bit, though I don't bother with as many irises as I grow. I do, however, make a point of sprinkling each clump individually rather than broadcasting the Merit to make sure each plant gets its full dose. It's important to water it in well if it doesn't rain soon after application.
Merit has conquered borers in my iris beds, and I currently grow about 600 iris cvs. Oh, and it does a good job of eliminating aphids on the irises, as well!
Laurie
thanks laurie. I had such dreams of beautiful iris and had them only one year. I bought them in a co-op here on DG run by Bleek and langbr and they were the most beautiful things in the neighborhood that spring.
But I got sick, and injured and was unable to get out and maintain the gardens like they should be cared -for, so things got out of control. Those bugs were huge by the time I found them, probably 2 years' growth I figure. Most of the rhizomes were total mush.
Is there anything I can do to cleanse the soil where they have left behind their mushy mess?
Oh janiejoy I'm so sorry. I don't know the solution to your problem but I can just imagine how sad and frustrated you feel. I love irises, too, and it's so sad to lose them to a bunch of ugly critters.
Mushy mess? Are you talking about the residue from rotting rhizomes? If so, clean it out of your garden and trash it. Dig up any irises that look like they may be affected, cut out the borers and any rotting iris flesh, do the bleach solution soak, rinse, and allow to dry for several days before replanting.
The borer life cycle works like so:
1) Borer eggs hatch as soon as temps reach 70 degrees in spring.
2) Newly hatched larvae bore into iris leaves and then gradually eat their ways down the leaves into the rhizomes where they continue to feed.
3) After eating their fill, larvae exit the rhizomes and pupate in the surrounding soil.
4) In late summer/early fall, pupation is complete, and adult borer moths (dull, grey, night-flying moths) emerge and lay the next generation of eggs on iris foliage and perhaps other plant debris, as well.
5) Eggs overwinter where laid and hatch the next spring when temps hit 70 degrees.
So, your best line of defense against borers is to do a very thorough garden clean-up in late fall and again in early spring to remove and trash/burn as many eggs as possible before they have a chance to hatch and start the cycle all over again. Between a thorough clean-up and application of Merit in early spring, you should be able to reduce or eliminate borer populations in your garden.
Unfortunately, if you have neighbors with irises or irises growing wild nearby, you'll probably always have borer moths finding their way into your garden to lay eggs, so this is something you'll have to handle every year.
It's bothersome but very doable.
Laurie
I clean a large amount of my garden plants out in November on a nice weekend. I trim all my iris blades down to a couple inches. I make sure I clean my garden debris every April. I then mulch my tender plants to protect from Spring freezes. I've started re-planting my iris in a mounded manner to keep them drier and discourage parasites.
I found a root borer in my neices over grown flowerbeds. Ugly little thing!
Is there anything I can use to kill the grubs now before they start to pupate? I'm finding several here and there, but my huge clump of Horny Lorri is almost completely wiped out.
And now that I have a bunch of new ones planted... Help!
All you can do at this point in the season is dig up the infected clumps, cut out the borers and rotted iris flesh, soak in bleach solution, rinse, dry for several days, and replant.
I don't know of anything you can use on the plants or soil that'll kill borer larvae once they've reached the rhizomes.
Laurie
Well...crud. I guess I know how I'll be spending my weekend.
Wanda--I thought I read in another thread that you leave your dead plant foliage to hold the winter mulch in place. Is that for plants other than iris? I'm such a copycat right now and I want to get it right.
Diane
Howdy, folks ~ I'm back after my 3 day safari in search of the elusive Iris borer. Boy, was I ever successful! What a nasty, gruesome task.
Yes, I know I should be severely chastised for my garden slovenliness, but I've paid the price and sincerely plan on this never happening again. At least not to this degree ~ gag!
This one was a little past due for maintenance, don'tcha think?
Moby,
It did make me gag!!!! How horrid that smell is.
I don't know how to get it out of my soil. Should I pour boiling water where they were?
I still have a lot of iris to pull up and clean out. I think there must be some way to cleanse soil. But what is it?
The weather is supposed to break this weekend and I'll be out there with my trowel...
Thanks for your help and support everyone.
Unfortunately, the bacteria (erwinia) that causes bacterial soft rot in irises seems to be endemic in many soils. I don't think there's any realistic way of getting rid of erwinia in soil ... no way that would be non-detrimental to the rest of the soil environment, anyway. Erwinia doesn't damage healthy rhizomes. It only invades rhizomes that have been damaged or weakened by other causes, such as borers. Borers don't cause rot, but the wounds they create in rhizomes leave perfect entry points for erwinia to attack the rhizome.
Once you eliminate borers in your garden, you won't see any more rot directly related to the damage they cause to your rhizomes. Of course, lots of things other than borers can weaken or injure rhizomes and leave them vulnerable to rot infections. That's what keeps iris gardening interesting. We are constantly trying to find rot-resistant cultivars that keep growing and blooming no matter what.
Hang in there. Irises are worth the effort.
Laurie
Janie~
I'm assuming the smell you're referring to is rot due to the borer damage. Bacterial soft rot usually enters the iris through a wound in the rhizome, in this case, wounding through borer damage.
You may check with your local nursery to see if there's an anti-bacterial solution you can soak the ground in. At the least, I would turn up the soil and let it bake in the sun for a while before you planted anything back in there.
If it were me, I'd rotate a completely different type of plant into that spot and plant my iris somewhere different.
Keeping the iris dry seems to be the key here.
I always remove any dying or spotted leaves as i dead head during the summer. I thin clumps that look too dense or cut the blades short to keep the airflow moving.
I leave alot of foliage intact in my gardens during the winters both as seed for the birds to help keep the mulch in place. My garden has quite a wind going thru it. I cut the foliage down to nothing & add mulch in March after I trim the trees. Gives me something to do when I'm itching to garden.
