skip to main content
Software
Integrations
Mobile App
Expert Support
All-In-One Platform for Construction and Design
See Pricing
Schedule a Demo
Talk to Sales: (888) 316-4595
My builder uses Houzz Pro to plan the timeline and give detailed estimates and daily updates with photos of progress, and provide invoices at pre-agreed key points in the build. This made the whole experience much more efficient and stress-free.
Steve W.
Client of Cribbs Construction
Learn More
Ideas
Discussions
Houzz TV
Houzz Research
Sign In
Houzz Logo Print
Explore DiscussionsFeatured Home DiscussionsFeatured Garden Discussions
Irises
redsun9

Lost Most Beard Iris Rhizomes this Year

12 years ago

I have two beds of tall beard iris. They are mature beds and crowded with rhizomes. They are over-due for digging and dividing.

But this spring, they did not come up much and did not bloom. The iris borers got them.

Since BIs are so relatively trouble free, I've not paid much attention over the past ten years. Never any problems. I believe I saw some sawdust type substance last year and that could be iris borers. Over the winter, I did not rake the mulch and leaves.

Anyhow, I just dug out the remaining iris rhizomes from the beds. Whatever remains are the very young shoots from the damaged rhizomes. Most of the rhizome roots are gone. I cut away the rotten part, soak the rhizomes in bleach. I've planted most of them and will replant the rest.

This spring, I think the borers may come back and I plan to spray. I believe after the rhizomes grow stronger and I clean the beds regularly, I may not need to spray next year. For about nine years, the BIs did very well.

The new plants may not bloom well, but they should be able to catch up very quickly.

Featured Answer
  • 12 years ago

    Instead of "spraying," consider applying nematodes that will attack the borers, applied right around the time temperatures range at or above 50 degrees F. The cost really isn't all that different than the chemical alternatives. The most common thing recommended for iris borers is Merit, a systemmic pesticide whick gets into the plant tissue. It is the systemmics that are causing the biggest problems for bees from what I understand. Iris are a flowering plant, and bees will be visiting the flowers - can't help themselves. I like the idea of using something that targets specifically the culprit - and nematodes do that.

    In my research for dealing with my borer problem, another thing to ensure is to remove all iris leaves and debris from the yard, and trim all the flags down to 4 to 6 inches right around this time of year. Apparently, borer eggs are laid on the tips of the flags in late summer, so trimming them and removing them from your yard should help reduce or eliminate nexts year's invasion. It's what I'm hoping anyway.

    Here's info sources:

    A summary of the study on the effectiveness of parasitic nematodes appeared in the Bulletin of the American Iris Society, series number 309, (April 1998), pages 35 to 37. Another version of the article can be found on the internet at www.agnr.umd.edu/users/ipmnet/98-2nmn2.htm A definitive article on parasitic nematodes by Randy Gaugler, Department of Entomology, Rutgers University, complete with color photos and a source list can be found on the internet at www.nysaes.cornell.edu/ent/biocontrol/pathogens/nematodes.html Dr. Parwinder Grewal, an entomologist at The Ohio State University, produced nematode reference center on the internet at www2.oardc.ohio-state.edu/nematodes/default.htm

    Parasitic nematodes are microscopic roundworms that feed on insects and have used successfully control insect pests. In a study reported in the April 1998, Bulletin of the American Iris Society, parasitic nematodes were shown to equal or more effective than Cygon 2-E or Merit. Cygon and imidacloprid (Marathon) both showed an reduction in borers of 87% while nematode Steinernema carpocapsae had a 100% reduction and nematode Heterorhabditis bacteriophora gave an 87% reduction.

    I hope this helps!

    Comments (12)

    • 12 years ago

      Those borers sound like a nightmare. This article helped me understand why it's so hard to be rid of them.

      Here is a link that might be useful: borers' life cycle

    • 12 years ago

      I'm so sorry you've had this problem. I feel very fortunate that I've never had iris borers (knock on wood!). I do try to clean up my iris beds in late fall & early spring, but as many iris as I have, I would have a problem. I hope your iris recover quickly.

    • Related Professionals

      Beaumont Landscape Architects & Landscape Designers · Fall River Landscape Architects & Landscape Designers · Minneapolis Landscape Architects & Landscape Designers · Edison Landscape Architects & Landscape Designers · Murrieta Landscape Architects & Landscape Designers · Ottawa Landscape Architects & Landscape Designers · Ocala Landscape Contractors · Augusta Landscape Contractors · Ashland Landscape Contractors · Gary Landscape Contractors · Lewiston Landscape Contractors · Palm Bay Design-Build Firms · Hopkinsville Design-Build Firms · Kirksville Design-Build Firms · Trenton Design-Build Firms
    • 12 years ago

      I just replanted, actually in larger beds. It is just that the plans are smaller and some won't bloom next year. I even gave away some to friends.

      I think I could have saved more rhizomes had I dug them in spring or early summer. But I would not have new beds for the roots.

    • 12 years ago

      Do you folks know if the Iris borers are the same buggers as the pumpkin vine borers? I also lost most of my kabocha pumpkins due to the vine borers. Regular haloween pumpkins did ok even with the borer damage.

    • 12 years ago

      Not the same critter!

    • 12 years ago

      Both are gross fat buggers.

      I only saw one iris borer after I dug. Most of them already escaped.

      I killed a lot of the pumpkin vine borers. Helped a little, but not enough.

      I figure the same chemical, Merit, can be used on the vine borers too?

    • 12 years ago

      If you use Merit for squash vine borers, realize that it will be in the squash you want to eat as well. It is a systemmic pesticide that gets into the plant tissue - that is why it is so harmful to bees. Most of the systemmics have warnings for you not to apply it around food crops, but it seems just as harmful to apply it around flowers, since they are visited by things we want in the yard. I grow daylillies in areas close to where I grow iris, and it is not unusual for me to pick daylilly blossoms to eat in the yard or add to a salad. If I use a systemmic to eliminate iris borers, there is a possibility it could get into my daylillies. I also have some fruit trees in areas where I have some iris growing - I'm not really interested in getting that stuff into my fruit trees - something that could be devastating to bees and to me. Like I said, the nematodes work just as well or better, and it seems at a similar price point, so why choose something so harmful. And please do not use Merit on things you want to eat. Check out this list of facts about Merit:

      http://www.flora.org/healthyottawa/merit-pesticide-insecticide-grub.htm

    • 12 years ago

      where can I buy these nematodes, drmbear? I also have problems with borers and rose midges.

    • 12 years ago

      Just search "Beneficial nematodes iris borer" and look for some good sources. Some of the articles about how this works provide sources as well. I'm buying along about April.

    • 12 years ago

      Where are you managing to get affordable nematodes? I've looked into them for years, but by the time they get here, the price is going to be well over $50. The killer is shipping, since they have to be sent overnight. And it certainly doesn't help that all the sources are on the West Coast.

    • 12 years ago

      Arbico Organics seems to have reasonable prices - the shipping for Garden size to VA is a little better than $16.

      http://www.arbico-organics.com/

      SIZES & COVERAGE RATES
      1/2 Garden Size: $16.00
      5 million Nematodes -
      Treats approx. 1,600 sq. ft.
      Garden Size: $29.95
      10 million Nematodes -
      Treats approx. 3,200 sq. ft.
      Farm Size: $68.75
      50 million Nematodes -
      Treats approx. 1 acre
      Small Ranch Size: $198.00
      250 million Nematodes -
      Treats approx. 5 acres
      Large Ranch Size: $379.00
      500 million Nematodes -
      Treats approx. 10 acres
      Grow Organics seems a little higher:

      http://www.groworganic.com/

      They are also for sale on Amazon and eBay.

      I also found:

      http://thebeneficialinsectco.com/

      http://www.gardensalive.com/ has reasonable prices and shipping at about $10.

      http://www.gardeners.com/ has reasonable prices, though they seem to be out right about now (okay since I don't want any until April).

      Close to when I am ready to buy in April, I will build a simple spreadsheet to compare prices, quantities, shipping, etc., making sure I am getting the correct recommended types, Steinernema carpocapsae and Heterorhabditis bacteriophora, and find the right deal. I had been growing iris for almost 30 years without a single borer problem until the last year or so, so I am thinking with some good management and cleanup/trimming in the fall, and a treatment at the critical time with nematodes I should be okay for a few years, particularly since I dig and divide about every three years - another opportunity to treat.

    Related Stories
    FLOWERSPaint a Garden Delightful With Iris
    By Amy Renea
    Charming and colorful, irises propagate easily, are hardy in many soils and climates, and unfold with layers of beauty
    Full Story
    6
    PETSWe Want to See the Most Creative Pet Spaces in the World
    By Stacy Briscoe
    Houzz is seeking pet-friendly designs from around the globe. Get out your camera and post your photos now!
    Full Story
    89
    FALL GARDENINGReflecting on a Gardening Year
    By Benjamin Vogt / Monarch Gardens
    Mistakes and successes, surprises and comforts. The garden helps us grow in new ways every year
    Full Story
    34
    GARDENING GUIDESBoxwood: Still Shape-Shifting After 350 Years
    By Mary Jo Bowling
    Wild or mild, the humble boxwood still brings style and order to all kinds of gardens
    Full Story
    52
    GARDENING GUIDESGreat Design Plant: Iris Versicolor
    By Curtis Adams
    A versatile native iris for bridging wet and dry gardens
    Full Story
    12
    COLORBest Ways to Use Radiant Orchid, Pantone's Color of 2014
    By Jennifer Ott Design
    Learn how to work in this bold fuchsia-pink-purple successfully around the home, and give it a yay or nay in the Houzz poll
    Full Story
    118
    GARDENING GUIDESGreat Design Plant: Euphorbia
    By Annie Thornton
    The daring colors and low water needs of this tropical plant make it a favorite for injecting life into tired landscapes year-round
    Full Story
    11
    FALL GARDENINGWhy Fall Is the Best Time for Planting
    By Benjamin Vogt / Monarch Gardens
    Spring is overrated for planting. Starting plants in autumn has advantages for both garden and gardener
    Full Story
    118
    GARDENING GUIDESTexas Gardener's October Garden Checklist
    By J. Peterson Garden Design
    Earn a "free" bonus by dividing perennials, make planting a priority now for hardy growth next year and keep an eye on your lawn
    Full Story
    7
    FALL AND THANKSGIVING5 Container Gardens for Fall, the Holidays and Beyond
    By Le jardinet
    Make planting easy with a single container, year-round plants and a sprinkling of simple seasonal accents
    Full Story
    61
    Sponsored
    Trish Takacs Design
    Average rating: 4.9 out of 5 stars36 Reviews
    Award Winning & Highly Skilled Kitchen & Bath Designer in Columbus