My glads are blooming but the majority of the flowers are opening withered like they are already fading. They are wrinkled with grayish discoloring. The blooms pictured below are newly opened or opening.

Click photo for full size withered blooms

  • What disease is causing this?
  • How can I prevent it in the future?
  • Since I live in USDA zone 4 I dig up glads. Are these corms worth saving for next year?

1 Answer 1


Damage like that is often caused by Gladiolus Thrips (Thrips simplex). These are tiny insects that scrape the surface of the leaf or flower and drink the sap inside. The damaged areas are silver or brown in color; in a heavy infestation, the plant can be stunted or die.

They tend to hide under the leaves or in the flowers, so you can identify them by picking an affected flower and shaking it over a sheet of paper to dislodge them. A magnifying glass will help because they're tiny -- about 1/16" long.

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(Image from University of Minnesota Center for Urban Ecology and Sustainability)

Control can be naturally with ladybugs (if you can find them), or using chemical insecticides, but they produce several generations in a year so multiple applications will probably be necessary. Cold weather will kill them, but in your climate, leaving them outside will probably kill the Gladioli as well. If you had room in a refrigerator, you could store the corms in it: some searching indicates that 8 weeks at 40°F will kill them. Another method I see is to soak the corms for 6 hours in a dilute mixture of 4 tablespoons of Lysol per gallon of water immediately prior to planting.

Regarding saving the plants you have for next year, I don't think they look too far gone. If you can control the current population and stop them from overwintering either by cold storage or soaking in Lysol, then keep an eye on the plants as they're growing next year and treating them if you see signs of damage.

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