One of a number of different plant viruses can infect gladiolus plants depending on plant variety and weather condition.
Infections can range from severe to barely noticeable.
Leaves may be mottled, yellowing, thickened or stiff. Flowers may be streaked or spotted. Occasionally only the flower spike has stunted growth. Viruses are spread by aphids, which feed on diseased plants and then transfer the virus to healthy plants with subsequent feedings. The virus increases year after year in the corms, and successive plantings of these diseased bulbs cause flowers poor in quality.