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Damp-off—Trouble In The Seed Tray
by Fred Davis, MG, Hill Gardens of Maine (To view other articles, click: Archives)
Welcome through Fred's
Garden Gate! (Late winter, 2006) Soon, many of you will probably have vegetable and
flower seedlings popping up all over the place. The average Maine
home during early spring, however, is actually not the place where
young plants really want to be. It's either too dry, too hot, too
humid - too something!
All these too-this and too-thats can, in some cases, make life miserable for seedlings and houseplants. In other cases they can make life end! For example, high humidity, higher than recommended temperature and decreased or absent air circulation provide the perfect set of circumstances for the encouragement of an annoyance called:
Damp-off - Though most frequently experienced in seedling trays, damp-off can also infect and cause serious damage to softwood "tip" cuttings. It is actually a tiny fungus with the imposing name of Rhizoctonia and accomplishes its sordid task without warning and with alarming suddenness.
Stems of young seedlings become narrow and quickly turn black at the soil line and simply topple over. Once that damage is done, salvage of the infected plants is impossible.
Infection usually begins in a small, isolated spot, involving a few tiny plants but, if allowed, will spread rapidly to involve all seedlings in the container.
Being a fungus, spores (a little like seeds) can remain viable from one season to another in the residues of unwashed pots, flats and seedling trays. Spores can also be transferred from one spot to another in the air and on contaminated tools, gloves or hands.
Immediate attention at the very first sign of infection is critical. Scoop out all affected plants and a generous amount of soil, and burn it. Never put the infected material in a compost pile or toss it into the garden.
There are several products you can use to treat damp-off in its early stages, including chemical fungicides (which I don't recommend). Safers markets a more natural treatment which works well. If you're watching your pennies, however, very finely-powdered charcoal dusted on the soil surface is usually quite effective. Some gardeners have success using a light dusting of powdered sulfur.
A surprise came a few seasons back, when researchers found that Trichoderma - a fungus found in compost and some finely-shredded bark - is so active and aggressive that it out-competes Rhizoctonia. Seeding mixes with 40-50% compost or bark have fewer problems with damp-off.
At least one company is on the verge of marketing the Trichoderma fungus, and when I hear that it's available, I'll let you know. (Nothing for the small home gardener as of Nov, 2007, But there is Growmorerice.com that has it in larger quantities for farmers.)
Some tips that will help you avoid the disappointment of damp-off are:
Use only sterilized soil or mix for starting seeds or rooting softwood cuttings.
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