Strawberry diseases A Lecture on ToT By Allah Dad Khan

2. Strawberry Diseases
A
Lecture To ToT trainees ( FFS)
By
Mr. Allah Dad Khan
Provincial Coordinator IPM KPK
MINFAL Pakistan

3. Gray Mold of Strawberry
Symptoms Identification

Young blossoms are very
susceptible to infection. One
or several blossoms in a
cluster may show blasting
(browning and dying) that
usually extends down the
pedicel. Light gray masses of
dusty spores soon appear and
are easily dislodged and
carried by air currents to other
blossoms. Such infections are
most common in well
protected areas of the plant,
where the humidity is high and
air movement is poor.
 Strawberry with Botrytis Fruit
Rot. Infected berries turn light
brown but remain firm. This
fungus produces a velvety
gray growth with powdery dry
spores.

4. Leaf Variegation or June
Yellows in Strawberries
Symptoms
Leaf variegation or June yellows;
healthy leaf to right
 Symptoms
Symptoms first appear in the spring on new
unfolding leaflets. A puckering and distortion
may occur in leaves with a "white streak" type
of variegation in early stages of the disease.
The leaves become irregularly mottled,
streaked, or spotted with golden or pale
yellow-to-white and light green areas (Figure
1). A slight loss of plant vigor accompanies the
color change. Variegation occurs mainly during
cool weather, when the temperatures are
below 50°F (10°C), in the spring or fall,
although some cultivars may remain mottled
throughout the summer. Variegation has been
observed only on the foliage and flowers –
never on fruit. All runners and daughter plants
produced by diseased plants are also
variegated with no reversion to a normal green
color. Seemingly healthy green plants may
become variegated at any stage. There is no
way to predict when a plant or its offspring will
become variegated.
 .

5. Strawberry Leaf Diseases
Symptoms Strawberry Leaf Spot
 Leaf Spot
This disease (Figure 1) is caused by the
fungus Mycosphaerella fragariae(imperfect
stage is Ramularia tulasnei). Leaf spot infects
leaves, petioles, runners, fruit stalks (pedicels),
and berry caps or calyxes. Small, dark purple
to reddish-purple, round spots, 1/8 to 1/4 inch
in diameter (3 to 6 millimeters), appear on the
upper leaf surfaces. The center of the spots
soon become tan or gray and eventually
almost white, while the broad margins remain
dark purple. Later in the season, dark specks
(sclerotia and/or perithecia) may be seen in
the older lesions. Indistinct, tan or bluish areas
form on the underleaf surface. The symptoms
on the other plant parts, except the fruit, are
almost identical to those on the upper leaf
surface. Only young, succulent plant parts are
infected by the leaf spot fungus.


6. Symptoms Strawberry Leaf Scorch
 . Leaf Scorch
The leaf scorch
fungus, Diplocarpon earliana,
attacks the leaves, petioles,
runners, pedicels, and calyxes of
strawberry plants. The fungus most
frequently infects strawberry leaves
at any stage of development. The
symptoms of leaf scorch (Figure 2)
are very similar to the early stages
of leaf spot. Round to angular dark-
purple spots, up to about 1/4 inch
(6 millimeters) in diameter, are
scattered over the upper leaf
surface. As the spots gradually
enlarge, they resemble small drops
of tar due to the production of large
numbers of minute, black, fungal
fruiting bodies (acervuli).

7. Strawberry Leaf Blight
Symptoms
Strawberry Leaf Blight
 Leaf Blight
This disease is caused by the
fungus Dendrophoma
obscurans. Leaf blight is
commonly found on plants after
harvest. This disease is
distinctly different from leaf spot
and leaf scorch. The enlarging
leaf spots are round to elliptical
or angular and 1/4 inch to an
inch in diameter (6 to 25
millimeters). The spots are
initially uniformly reddish-
purple, but soon develop a
darker brown or reddish-brown
center surrounded by a light-
brown area with a purple
border. Similar spots sometimes
develop on the fruit calyx.

8. Strawberry Red Stele Root Rot
Symptoms
Red stele infected roots. Note the
absence of numerous roots and,
particularly the discolored stele of
existing roots.

When plants start wilting and
dying in the more poorly
drained areas of a field, the
cause is frequently red stele.
Certain other symptoms are
more specific. A red stele
infected plant has very few
new roots, whereas the roots
of a healthy plant are thick
and bushy with many
secondary roots Infected
strawberry roots will appear
gray, while the new roots of a
healthy plant are yellowish
white.

9. Verticillium Wilt of Strawberry
Symptoms
Strawberry plant
affected with Verticillium
wilt. Note wilted and
curled leaves

Verticillium wilt often
appears in new strawberry
plantings as runners begin
to form. In older plantings,
the symptoms usually
appear just prior to picking.
The aboveground
symptoms vary with the
susceptibility of the cultivar
and cannot be easily
differentiated from those for
red stele. black root rot, or
winter injury. A laboratory
culture is necessary for
positive identification.
 .