Oh boy -- what fun, eh? Not...................

Here are a few:


A rhizome the spring after treatment and replanting leaving rhizome mostly out of the soil


Mr or Mrs Borer in the rhizome shown above


The removed, but unsquashed, adult borer

Good morning everyone. I have been absent here for quite a while and haven't garden for almost two years. My irises are infested with borers. I read a lot of good advice from this thread. Thank you so much.

Oh Lily -- I'm so sorry to hear that. I dealt with them too, when I lived in DuPage County. Hope you were successful in eliminating them.

They are here in KY also. I used a new chemical this year and have had very few so far this summer. I think the key is putting the stuff on in the early spring to catch them when they are very small or just hatching. Even squashing them does not work when they get bigger, have to behead them. I do not think that adding anything after they are already down in the fans is useful. Someone correct me if I am wrong. Destructive little buggers....I am vigilant daily searching for signs. My husband thinks I am praying over them...Ha.

You need to get them in the spring before they hatch. I use a systemic which the iris plant takes up. If there is enough in the plant, the borer will not live long. If you miss an area or do not put enough down (or are late in application) then the buggers have a good chance to kick ass. Even though I seem to be reporting lots of damage from them, I feel that I am having a very minor out break and that my issue is a spotty application (especially based on the concentrations and abrupt change over to rhizomes with no problems).

Ya -- but Greg -- don't the systemics transfer to the bees when they feed on the blooms? That worries me...............

yes. Might try the nemotodes.

Thanks MaryAnn. I think it's too late and I need to dig and save whatever I can. Another problem is that it keeps on raining here. Will update in a week or two.

Lily -- when we had them, I dug every rhizome and dunked in a bucket of bleach water. Pretty soon there were dead borers floating on the water. I replanted the rhizomes -- and every one of them lived!!

That's what I am going to do. Thanks again!

Good luck. Let us know how things turn out, ok?

I probably could have gone without seeing those ugly things Here in normally arid southern Colorado, I've never seen them, but given our very wet spring and the beginnings of a damp summer, I now know what to look for.

Just an update from last year. Apparently, they will attack any type of iris of rhizome plant. I almost lost my Toad Lily. I noticed it never bloomed and that it was looking very yellow. Well, I decided to dig it up and see what the issue was and guess what? - 2 big borers were eating through the rhizomes and had destroyed nearly the entire plant. I was able to save only 2 small rhizomes and will be planting them again soon. I dug out almost my entire Iris bed this year and killed a couple of skinny borers and tossed out the old original rhizomes. I did not find that many though. I didn't think they would attack another type of plant...I will probably not have any blooms next year, and will probably give up on my Iris bed as it is a lot of work.

I hope the hybridizers work on some borer resistant varieties if such exists!! They are mostly in the NW where they do not have borers (west of Mississippi or the Rockies, not sure which) so do not have to deal with them. I had borers in my LA irises this year for the first time. I have not seen any in Sibs but know they can get in them.

I didn't realize that they would eat the toad lilies. Some people have had good luck with nematoads to fight borer. You apply them in the spring. When you do weeding in Aug., watch out for the brown pupae & destroy those.

I think they will 'eat" any of the irids that come from a rhizome, Lucy. In reading through all the "back issues" of the AIS bulletins, it's astounding how much 'ink" has been used on the "iris borer".... ....it's been a big problem for a long time

Northern Illinois is a hotbed for borers, Lynette. You don't have to give up your Iris bed -- just apply some defensive products to prevent them. Seems like there's something in nature to challenge us in every area of interest.................

I have to add my 2 cents worth since I just destroyed a couple of borers in my garden yesterday. I was checking my plants after I had dug up and replanted all my irises 2 weeks ago. Thought all would be good as I dug deep and amended. I saw some tell tale rotted type of mess on a few leaves of increases. I cut with a knife to sever the increase and there is the borer eating his way into the main rhizome!! Beheaded both and the roots of the increases look good so I replanted. I thought July was too late for them to be still moving in but I guess not!

I think that borers are still active into August when they pupate and turn into little brown cases in the soil. I have not seen any so far in that stage. That is why digging around to share or divide in August is good for finding those if you know what to look for. I think late August and September is when the moths emerge and lay eggs.
I am still finding some borer activity even though I have put down chemicals several times. You have to be vigilant.