I just stumbled upon this forum and joined. I'm hoping you can help me with some advice. I've had an iris bed in my backyard for a number of years. Almost every year we made it bigger to accommodate my latest purchases! As late as 2017 the bed was a showstopper of beautiful blooms. That fall I added 12-15 new plants.
Last year (after a hard Wisconsin winter and spring) I had only about 5 or 6 blooms. Heartbreak! "Everybody" said it was because of the winter and the flowers will be back next year. The newly planted ones barely made a showing of leaves. Then in the fall, I discovered a few borers 😳 in the bed. We pulled out plants and got rid of the mushy parts, cleaned up debris, etc. This year, my bed looks pretty sparse and sad. I miss the days of all those blooms. Will they ever be back or should I give up on the iris bed? They are my favorite flower. Any thoughts? Thanks!

When rhizomes become overcrowded, they have a tendency toward borer and rot. And borers promote rot, too..

Every 2 to 3 years you should use a garden fork to lift all the rhizomes, soak them in a mild bleach solution for 10 minutes. Then inspect them for tiny borer holes and rot. Cut out and destroy any affected rhizomes. Replant, spreading them out a bit. I make sure that the ends of the rhizome with active growth always point outward from the center of the clump, so that the center is less likely to become congested quickly. Give them an iris fertilizer early next spring. And next spring consider using either BT or a neem spray, or alterating those, to help kill borers before they get tunnelled in. If they do, and you start seeing streaks on the leaves, start using the squeeze and pop technique.

If you do these things, I think your irises will reward you in future.

NGoodman, welcome to the Iris Forum!

NGoodman ~ to the Iris Forum!

ngoodman, nice to see another Wisconsinite join the group. Iris borers lay their eggs in the fall on the iris foliage. If you want to go chemical free, as some do, it's good to always keep the dead leaves pulled off the plants early in the spring, as many of the eggs may be on them. The spent leaves should be burned or put in a bag and taken to the landfill. Don't compost them as they may hatch and come back to haunt you. Some people actually burn their iris beds in the spring, not everyone can do that depending on your situation. It also is possible to see the affected leaves chewed on by the borer, and you can sometimes squash the little bugger inside of the leaf. This of course is not something I can do with over 600 plants. If you are not averse to using chemicals, you can treat your iris beds in the early spring with Bayer Grub killer, the stuff that's made for lawns. Sprinkle it around each plant in the spring before we have a stretch of 5 to 7 days without frost. That's when they hatch. This systemic gets into the plants and as the baby borer starts munching on them they get the poison. It's not too late to do the treatment now if you choose. As for soaking in bleach, besides being very labor intensive, that may kill lots of things, including helpful bacteria that the plant needs to produce food. People have varying views on doing that. Regarding the use of fertilizers, it is a good practice to have your soil tested before you add anything. Just random addition of fertilizers may or may not give your plants what they need including your soil's PH levels. Our ground water supply is already over saturated with nitrates and phosphates, so adding them where they are not needed only exacerbates that issue. That soil test can be done cheaply through your county agents office. Hope this is helpful, and that you have a good year gardening.

Welcome to the iris forum, ngoodman!

Some very good advice there and I, like Tom, cannot lift and treat each clump so the borer treatment would have to be the way to go. Also, very good advice on fertilizing your plants. Know your pH before you feed. If your soil pH is off the plants cannot take up the food and it runs off into our waterways. good luck.

ngoodman

ngoodman. this is a very helpful group and take a look at the other's posts of their blooms. it may help fill the gap, until yours reward you. irises are a pretty hardy bunch. hope you'll be able to save yours from the dreaded borers!

ngoodman

Welcome to the forum, ngoodman!

Welcome to our forums. Irises should be divided every 3 yeas so it is a good time to check for borers. You might check into using neotobes (check spelling on that) if you don't care for chemicals.

irisarian said:Welcome to our forums. Irises should be divided every 3 yeas so it is a good time to check for borers. You might check into using neotobes (check spelling on that) if you don't care for chemicals.

Lucy ~ Did you mean nematodes?

https://www.gardensalive.com/p...

There has already been some good advice, and tips, so, ll I will do is "second" what Tom said about a soil test, before fertilization.

correct Evelyn

Warm welcome ngoodman

Another

Ngoodman!

Tom's advise (If you are not averse to using chemicals, you can treat your iris beds in the early spring with Bayer Grub killer, the stuff that's made for lawns) is great advise.

I've been using the Bayer Grub killer for years now. I make sure I apply it before the temperature reaches 70 degrees. That's when the little buggers hatch.

The best way for me to look for borer damage is to pay CLOSE attention to the "center" leaves on the iris fan. That is where the damage begins to be apparent.

I NEVER even heard of the iris borer until a year after extra heavy rains came here in Wisconsin (the kind that washes out roads). I believe that was in 2008??? The following year I started to have a few stalks rot and fall over. I started to research it and dug up an iris...and sure enough there the little bugger was. After getting it under control, I've applied the Bayer product every spring. I still keep an eye out for it. Don't let your guard down.