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Is this problem borers or rot?

17 years ago

Two years ago we discovered we had iris borers. We dug our two 40' X 4' beds, cleaned out any bores we saw, cut out the mushy smelly parts of the rhizome, soaked them in a bleach solution, then dipped them in a insecticide solution, dried them and replanted them. Then we sent for some beneficial nematodes and applied them. Last year we applied the nematodes again. This year we have mushy smelly rhizomes again. Is this rot or bores? I need some advice on using one of these beds for daylily seedlings I have started and need a home to grow. Will either the iris rot or bores affect the daylily babies or adults? Any help/suggestions will be greatly appreciated. Thank you, Joan

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Comments (3)

suenh
17 years ago
It could be both., but the borers aren't going to be very big this time of year yet.
Spring was wet, wet, wet. We broke all records on rainfall since 1871. I lost a lot of iris this year. Even in beds that are slightly raised and some that had drainage trenches dug around them. I also had a thick, suffocating layer of ice all winter rather than snow.

The iris problems won't bother the daylilies. The daylilies seem to be able to take a bit more moisture. Mine got off to a very slow start but are catching up now.

Hasn't been very good iris weather in the northeast. You can drink the air right now.

I haven't had much luck controling borers organically. I'm afraid I have to breakdown and use a systemic insectide every couple of years. The cleanup and hand squishing worked when I only had a few iris. Now it's too much.

If your iris aren't raised a bit I'd raise them after bloom. Apply a fungicide of some sort. Garden sulfur works fine if you follow it with lime about 2 weeks after. The sulfur is acid and the beardeds prefer it a bit alkaline. If they are beardless don't use lime. Sets them back bad and sometimes kills them.
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njiris
17 years ago
Borers cause rot, so you really can't tell unless you examine more closely for the grubs.Look for chew marks and/or weepy marks on foliage. I agree that at this time of year, the borers are still small and have not eaten their way down to the rhizome yet, so rot from borer is not likely. You probably need better drainage.
Laetitia
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I have a small bed of bearded iris on a slope. They haven't had mulch the past few years, and are not very deeply planted at all. In the past, they have bloomed wonderfully, but the last 2 years there's been nothing. The plants leaf out well, they just don't bloom. I thought they might be overcrowded (anyone with a link to what this looks like?), so I dug some up this weekend. I found several leaves with a little yellow streaking, but otherwise in good shape. However, every single rhizome had either a rotten end or a dried up section. None of the rhizomes were very large, although the plants are normally sized. Is this borers or something else? Considering the drought we've had for most of a year, it's a wonder the plants are even alive - they don't get any extra watering. The bed drains quickly, so I don't think it could be water rot. However, I didn't see any bite marks or caterpillars, just holes in the dead tubers where I think the root had been. ANy help is appreciated.
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joan_me_coast
Original Author
17 years ago
Thanks so much for your information and advice. My bearded irises are in raised beds on top of our septic leach field, since the iris roots are shallow, they stay right in the 6 + inch raised bed. The Siberians and Japanese iris are in another moist location. With all the moisture this year, my roses already have black spot, I have 223 roses of all types. More rain this weekend, just what we DO NOT need.
Thanks again,
Joan
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