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Cass County Extension

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Gladioli Thrips

Thrips may prevent the gladioli flowers from opening and distorting the blooms that do open. The leaves of the plants are streaked with white areas. A very tiny insect, the gladiolus thrip is responsible for this damage. The insect overwinters in the gladiolus corm and sucks sap from the plant during the growing season. This sucking of the sap causes the white streaking on the plant leaves. Their feeding also causes deformed blossoms. The thrip is about 1/16 of an inch in length and brown in color.

The gladiolus thrip can be controlled in the growing plant as well as in the harvested corm. To protect the plants, spray or dust the gladiolus when they reach 6 inches in height and continuing treatment every 7 to 10 days until flowering. Diazinon should be used for control. Other insecticides labeled for thrips such as Tempo can also be used, but only for plants listed on the label. The active ingredient in Tempo is available in Bayer Advanced Garden Multi-Insect Killer.  When using insecticide, mix and apply according to label directions. After harvesting and curing the gladiolus corms, shake them in a sack with a small amount of 5% Sevin dust (1 - 2 teaspoons for each 100 corms) and store as usual. This procedure will control the thrips in the over wintering corms.

Todd Weinmann, Extension Horticulturist & Master Gardener Coordinator
Phone: (701) 241-5707

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