Solving Colchicum Problems

Colchicum Problems
SymptomsProbable Cause
Brown Spots On Leaves and StemsFrost Injury
Plants Stunted; Yellowed; Root LesionsBulb Nematodes
Foliage Distorted; Corms DecayedBulb Mites
Ragged Holes In LeavesSlugs and Snails
Corms Gnawed; Unearthed Or EatenRodent Injury (see below)

Brown Spots On Leaves and Stems Caused By Frost Injury
Colchicum leaves caught by late spring frosts may show small brown spots that later merge into blotches. They sometimes split and look ragged. Prevent this by laying down a mulch layer over the corms right after the ground freezes in the fall.

Plants Stunted; Yellowed; Root Lesions Caused By Bulb Nematodes
Bulb nematodes and root knot nematodes may attack colchicums. Nematodes are not insects, but slender, unsegmented roundworms. Most are microscopic-sized soil-dwellers. They have piercing-sucking mouthparts and feed on plant cells. Infested colchicums look sickly, wilted, stunted, with yellowed or bronzed foliage. They decline slowly and die. Their root systems are poorly developed, even partially decayed and their corms are damaged. Dig up and trash damaged corms. If possible, add lots of compost (especially leaf mold) to the soil to encourage beneficial fungi that attack nematodes. See the file Controlling Nematodes

Foliage Distorted; Corms Decayed Caused By Bulb Mites
Bulb mites, about 1/50 inch long, are almost invisible. They have four pairs of legs, piercing-sucking mouth parts, and very compact bodies. Below ground, they cause scales of infested colchicum corms 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. Control mites by destroying all infested corms. Soaking other dormant corms in hot water (110° to 115°F.) for 3 hours. See the file Controlling Mites

Corms Gnawed; Unearthed Or Eaten Caused By Rodent Injury
During the winter months, small rodents such as mice and voles 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 their roots to spread into the soil beneath. Lay one-inch wire mesh over bulb beds and fasten it to the soil with pegs to discourage squirrels and chipmunks from digging up corms.

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