Sanitation is the first step. This means using clean
materials when you plant: clean seed trays, clean soil and disease-free seeds. If
you choose to reuse seed trays, tools, and tags, be sure to bleach (1 cup bleach to 9 cups water)
for at least 10 minutes before you use them. Many microbes, good and bad,
produce structures similar to seeds called spores to reproduce and survive when
conditions are bad. These spores will germinate when conditions are favorable. The active ingredient in bleach can penetrate the surface
of these spores and kill them after soaking for approximately 10-30 minutes. Even
if you sanitize everything, potting mixes can contain soil or compost that have
their own microbes that might take advantage of your seedlings.
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| Pepper seedlings with early damping off symptoms (wilting plants and losing leaves) |
Starting off with clean materials is a great way to begin, but there is more. Watering is another point of prevention. Too much or too little water can
stress your seedlings. Remember how your immune system is lowered when you are stressed? Plants don't have immune systems like ours, but stressed seedlings
are also far more susceptible to infections. In general, it is good to have moist,
but not saturated/water-logged soil. Water plants through the bottom of the
tray, allowing the water to be absorbed up into the soil. Watering from the top
can increase the humidity in the leaf canopy. Root diseases, like damping off,
are more common when the soil is saturated, but leaf diseases, like leaf spots,
often need warm humid leaf canopies. If you have to water seedlings from the
top, try to promote good air flow by using a fan.
Temperature is an often-overlooked component of disease
prevention. Microbes, like plants, have minimum growing temperatures, maximum
growing temperatures and optimum temperatures. Many (not all) seedling diseases
like cooler temperatures. Keeping your soil warm (but not too warm) will help
your seeds germinate faster and reduce the chance of disease occurring. When
you plant, keep the temperature above 65 degrees.
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| Tomato seedling suffering from damping off (brown squishy stem near soil) and adventitious roots (white roots on stem) right above the diseased tissue. |
Checking or scouting your plants is the last step to managing
seedling diseases. Check your plants daily to look for indicators that something
is wrong. If you see a seedling that is wilting, even though it has plenty of
water, it may have the seedling disease called damping off. I know your first
reaction when you see a wilting plant is to give it more water, but don’t.
Check to see if the soil is damp. If it still has plenty of water move the plant (and the
surrounding plants) away from the rest of your seedlings. This will help reduce
the microbes spreading to your other seedlings. If they continue wilting, go
ahead and throw them away, you can’t heal a sick plant. Don’t bother composting your diseased
plants; most microbes have survival structures that can persist through
composting. Bag them up, say a few last words, and put them into the city trash.
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| Healthy pepper seedlings |
If you garden, chances are you will end up with disease at
some point. Taking steps early on to prevent disease can help minimize your
losses during the growing season. Giving your plants proper light,
temperatures, wind (using a fan), and maintaining appropriate moisture will give them a great start and reduce their chances of getting disease.
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