Insect and Disease Control Thrips are the major insect problem of gladiolus. They are tiny insects that are difficult to see with the naked eye. Thrips cause white streaks on the leaves. Flowers often are misshapen, streaked, discolored and occasionally will fail to open. Continue treatment every seven to 10 days.
Thrips can overwinter on stored corms.
Use 1 to 2 teaspoons for each 100 corms. Try to plant them in a different location each season to help control thrip populations, but also to control Fusarium wilt and other viruses. Immediately lift and destroy any plant that turns yellowish and looks stunted. Cutting Gladiolus Blooms Cut the glad spike when one to three florets are open. The rest will open in turn.