Janna Beckerman, Assistant
Professor of Plant Pathology, Botany & Plant Pathology Department,
This is the time of year when
growers begin planting seed—whether
you are child planting a few seeds in Dixie cup for a school project,
home tomato growers, or professional horticulturists. Unfortunately,
one problem you may share in common is damping-off. Damping-off describes
the death of seeds or seedlings and includes all of the following
phenomena: Seeds that rot before they germinate, the newly emerging
root (radicle) or shoot (cotyledons) of the seedling rots before
emergence, or stems of seedlings (cotyledon) are attacked near the
soil line, causing the young plants to collapse. Damping-off is caused
by several fungi, including Botrytis spp and Rhizoctonia
solani, and fungal-like organisms such as Pythium spp. and Phytophthora
spp. These microbes are found in practically all soils
and pose a large threat to plant propagation. Almost all species
of plants can be infected, and these organisms also cause new
cuttings to rot, as well.
large flats or direct seeded gardens, damping-off commonly occurs
in patches. Pre-emergent damping-off describes a seed rot, or
the death of the seedlings before they emerge from the soil.
Post-emergent damping-off affects newly developed seedlings that
have emerged from the soil. Symptoms of post-emergent damping-off
usually involve a dark stem rot near the soil surface that causes
seedlings to collapse and rot.
this case, disease prevention is a cornerstone of management.
If planting in the garden, sow seeds when temperatures are favorable
for rapid seedling growth. When starting seedlings indoors or
in a greenhouse, this disease can be avoided if seeds and cuttings
are planted in sterilized, soil-less seedling mix or other planting
media, using only sterilized containers. A soil-less starting
mix composed of a peat moss/vermiculite/sand mix is preferable
for starting seeds. Use clean water on the seeds, not stored
rainwater or pond water. Remove any pots or flats with damping-off
immediately to prevent the spread of this problem.
As always, promote healthy plant
growth--Vigorously growing seedlings are fairly resistant to
infection. Follow planting instructions carefully—some
seeds require light, a certain planting depth (or no depth!), soaking
overnight, scarification (nicking the seed) and stratification (cold
to induce germination). For plants that should not be covered,
or require light for germination, plant seeds on soil, but cover
with a light layer of sterile sand instead of soil. Provide good
ventilation--moving air allows seedlings to dry and prevents the
germination of Botrytis, or free water needed for Pythium or Phytophthora infection.
Do not overwater, and follow instructions to thin seedlings appropriately.
Yes—kill your darlings to the recommended spacing to allow
them to grow big and strong, and not topple over because they are
spindly and weak!
Finally, if you are faced with
persistent problems, consider using fungicide-treated seeds,
or adding captan to seeds prior to planting. Follow labeled recommendations
as rates change depending upon type of seeds being treated. Keep
in mind that certain seedlings (e.g., conifer) may be adversely
affected by this fungicide.
Click image to enlarge
Damping off seeds
Damping off stem
Damping off pansy tray