Solving Gladiola Problems

Gladiola Problems
SymptomProbable Cause
Foliage Distorted; Corms DecayedBulb Mites
Leaves Silvery; Flowers MalformedThrips
Plants Stunted; Yellowed; Root LesionsNematodes
Watersoaked Spots On CormsCorm Scab
Corms Gnawed; Unearthed Or EatenRodent Injury

Foliage Distorted; Corms Decayed Caused By Bulb Mites
Bulb mites are about 1/50 inch long, barely visible to the unaided eye. Related to spiders, they have 4 pairs of legs, piercing-sucking mouth parts, and very compact bodies. They attack below ground on gladiolus corms which become hard and light chocolate-brown colored. The dried corm pulp breaks up into corky fragments, on which hundreds of mites feed. Mite damage also opens the way for other pests and diseases. Control them by destroying badly infested corms, and soaking other dormant corms in hot water at 110° to 115°F. for 3 hours. For more information see the file on Controlling Mites

Leaves Silvery; Flowers Malformed Caused by Thrips
Thrips are tiny, narrow, 4-winged insects, about 1/16 of an inch long. They hide between new leaves and flower petals, and injure tissues by rasping at them and lapping up the sap that oozes out. They damage leaves, abort flower buds and shrivel flowers. Thrips are the major insect pest of gladioli. They overwinter on stored corms. Control exposed thrips on plants with a synthetic insecticide. Dust corms with rotenone dust before storing, or soak them in Lysol (4 teaspoons to 1 gallon of water) for 3 to 5 hours before storing or planting. Dry treated corms before storing. For more information see the file on Controlling Thrips

Plants Stunted; Yellowed; Root Lesions Caused By Nematodes
Both bulb nematodes and root knot nematodes attack gladioli. Nematodes are soil dwelling, slender, unsegmented roundworms. Most are microscopic-sized. They have piercing-sucking mouthparts and feed on cell contents. Infested gladioli look sickly, wilted, stunted, and show telltale yellowed or bronzed foliage. They decline slowly and die because their root systems are poorly developed, even partially decayed. Their corms are damaged. Control nematodes by digging up and trashing damaged corms, and by adding lots of compost (especially leaf mold), if it is available, to the soil to encourage benficial fungi that attack nematodes. Liquid fish emulsion diluted with water and poured on the soil around infected plants will often repel nematodes. For more information see the file on Controlling Nematodes

Watersoaked Spots On Corms Caused By Corm Scab
This fungus disease causes sunken, black, shiny-surfaced lesions to form on gladiolus corms. Leaves turn yellow and die prematurely. The disease most often breaks out in warm, wet weather, and may be transmitted by bulb mites. Destroy infected corms. Dip healthy corms in Benlate solution before planting or storing, and thoroughly dry corms that are to be stored. For more information see the file on Controlling Fungal Disease

Corms Gnawed; Unearthed Or Eaten Caused By Rodent Injury
During the winter months, small rodents such as mice eat corms. Moles tunnel through beds in search of earthworms and insects, but mice also use their tunnels to get at the corms. Control these animals by lining your planting holes with small baskets of 1/4-inch hardware cloth cut to fit. Or, try planting individual corms in tin can "sleeves" cut open at both ends and sunk into the soil so that the top rim is just covered. Set corms near the bottom of the can to allow the roots to spread into the soil beneath. For more information see the files on Dealing With Mice and Dealing With Voles