basics of plant diseases
“The wilt diseases,
caused by either fungi or bacteria,
enter the roots and grow into the vascular system-the
water and nutrient-conducting cells.”
If the symptoms you observe are on
young seedlings that came up and then
fell over (called damping-off), or the
seeds never germinated in the first
place (called pre-emergence dampingoff), you should see that as a sign of an
infectious agent that attacks seeds or
young seedlings. If the plant suddenly
wilted and died after growing for a
while, then you should consider other
so-called wilt or root rot diseases.
Sometimes the foliage exhibits some
changes in coloration or some twisting
or other deformation of the foliage.
The color pattern may be a mosaic
of green and yellow, or some other
symptom, such as a leaf mottling or
streaking, often occurring with most of
“Virus disease
symptoms may
be confused with
those caused
by nutrient
deficiencies.”
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the plants. This suggests the possibility that the causal agent is inside and
throughout the plant, and that the disease is caused by a virus. Virus disease
symptoms may be confused with those
caused by nutrient deficiencies.
Where plants are close to each other,
such as in lawns, the disease may
occur on multiple plants and appear
to be spreading from one plant to its
neighbors. In examples involving turf
grass, the plants are very close and
symptoms will be expressed by the
group of plants.
When individual plants suddenly wilt
in spite of the soil being adequately
irrigated, one might suspect that
the plant contracted a disease from
the soil. The wilt diseases, caused
by either fungi or bacteria, enter
the roots and grow into the vascular
system—the water and nutrientconducting cells. The pathogen can
grow up the vascular cells and build
a blockage that impairs movement of
water up from the soil into the plant.
Generally, individual plants exhibit
wilt symptoms unless the pathogen
has been well dispersed in the planting soil and infects multiple plants.
Mosaic disease on the leaf of
a cucumber plant, caused by
the cucumber mosaic virus.
A patch of turf grass where
multiple plants are showing
the signs and symptoms of
a disease, compared to the
healthy plants surrounding the
patches.