How to Kill Thrips on Glads

Despite their small size, thrips will cause extensive and devastating damage to gladiolus plants if left untreated. Thrips make their presence known when damaged or malformed flowers emerge from their sheath, often with small silvery spots, crimped petals and noticeable discoloration. While somewhat time consuming, killing thrips is not difficult to do with the right tools and technique. However, you must be persistent in your treatment and vigilant for signs of further infestations to ensure the continued well-being of your glowers.

Pruning shears
Garden trowel
Bucket
Isopropyl alcohol
Mesh bag
Refrigerator
Insecticidal soap

Instructions

- 1
  Cut back all the affected gladiolus plants to ground level using pruning shears. Discard the affected plant matter in a green waste bin rather than adding them to your compost.
- 2
  Dig up the gladiolus corms in early winter using a garden trowel. Lift the corms from the soil and spread them out in a bright, well-lit area. Inspect each for signs of thrips such as dark spots or a sticky feel. Discard the corms with obvious signs of infestation.
- 3
  Mix 4 teaspoons isopropyl alcohol and 1 gallon water inside a bucket. Soak the gladiolus corms in the solution for six hours. Dry the corms on a sheet of newspaper for two to three hours.
- 4
  Place the gladiolus corms inside a mesh or paper bag. Place the bag inside a refrigerator or outdoors in an unheated shed where temperatures will stay between 35 and 40 F for four to six months. Do not allow the corms to freeze.
- 5
  Transplant the corms into a garden bed after their period of cold treatment. Spritz the emerging foliage with insecticidal soap once a week for the first month to dissuade any lingering thrips from colonizing the gladiolus plants.

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