Problems of Crocus
Symptom	Probable Cause
Corms Gnawed; Unearthed or Eaten	Mice or Voles
Leaves or Stems Browned; Distorted	Environment
Ragged Holes in Leaves	Slugs or Snails
Watersoaked Spots on Corms	Corm Scab
Flowers; Petals Streaked with Color	Mosaic Virus

Corms are Gnawed or Eaten by Rodents.
During the winter months, squirrels and small rodents such as Mice and Voles eat corms. Voles borrow underground mole tunnels to get at the corms. Discourage 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.

Another alternative is to add some sharp, crushed gravel to the planting hole. Afterward, lay one-inch wire mesh over bulb beds and fasten it into the soil to discourage squirrels and chipmunks from digging up corms from the soil surface.

Browned, Spotted, Distorted Leaves and Stems are from Environmental Conditions.
Crocuses caught by late spring frosts may have small brown spots on their leaves or petals that later merge into blotches. Sometimes leaves split and look ragged. Prevent this by laying down a mulch layer over the corms right after the ground freezes in the fall.
Fallen leaves permitted to accumulate and become matted from repeated rains and snows may become a sodden mass that smothers newly emerging crocus sprouts in the spring. Rake these leaves up during fall clean up before frost. Mulch only with chopped leaves or other organic materials that permit water to soak into the soil and do not mat.

Plants are Stunted, Distorted; Corms Decayed from Bulb Pests.
Bulb nematodes and root knot nematodes sometimes attack crocus corms. Nematodes are not insects, but slender, tiny unsegmented roundworms. Most are microscopic soil-dwellers. They have piercing-sucking mouthparts and feed on plant cells. Infested crocuses look sickly, wilted, stunted, with yellowed or bronzed foliage. They decline slowly and die. Their root systems are poorly developed, even partially decayed, and corms are damaged.

Bulb mites are about 1/50 inch long and are almost invisible. They have four pairs of legs, piercing-sucking mouth parts, and very compact bodies. Below ground, they infest crocus corms, causing their scales to become hard and light chocolate-brown colored. Hundreds of mites feed on their dry and crumbly pulp. Mite damage also opens the way for other pests and diseases.

Dig up and trash corms damaged by nematodes or mites. Adding lots of compost, if it is available, to the soil encourages beneficial fungi that attack nematodes. Soaking questionable corms in very hot water discourages mites. However, the best and easiest control is to simply plant crocuses somewhere else for a few years.
For more information see the file on Controlling Mites or on Controlling Nematodes.

Watersoaked Spots on Corms Signals Corm Scab.
This fungus disease causes sunken, black, shiny-surfaced lesions to form on corms. Crocus leaves turn yellow and die prematurely. This 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 any corms that are to be stored.

Flowers, Petals Color Streaked from Mosaic Virus.
Once thought to be a desirable trait, this streaking disease weakens crocus plants. Discard affected plants. Sterilize tools used to dig the diseased corms by dipping them into a solution of hot water and household bleach. Control aphids if present, and keep weeds down.