Biology Reference
In-Depth Information
Leaf Scorch
Curvularia
According to the dictionary scorching means to
heat so as to change color and texture without
consuming. Sometimes leaves are literally
scorched in summer heat, and sometimes symp-
toms caused by fungi resemble those of a heat
scorch. This section includes some of the latter.
Blights
.
Curvularia sp
Leaf Scorch
on pecan.
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Diplocarpon
Ceratocystis
Blackspot
.
Diplocarpon earlianum
Strawberry Leaf
Scorch
, general where strawberries are grown
but more prevalent in the South. Dark purplish
spots about 1/4 inch in diameter are scattered
profusely over upper surface of leaves in all
stages of development. Later the spots enlarge
to scorch wide areas of the leaf, and black
fruiting bodies give a “tar spot” appearance.
Scorch spots always lack the white centers so
characteristic of Mycosphaerella leaf spot on
strawberry. Lesions are found on petioles, sto-
lons, and fruit stalks as well as leaves. If the fruit
stems are girdled, flowers or young fruits die.
Rarely the disease appears on green berries
as a superficial red or brown discoloration
and flecking. Spores, produced in quantity in
acervuli on lesions, are distributed by birds,
insects, and pickers on tools and clothing. The
fungus winters in old leaves. Teleomorph and
anamorph states are both produced in spring,
and repeated infections occur throughout the
summer in moist weather.
Control
Remove all old leaves when setting
plants in spring. Spray with bordeaux mixture at
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Cankers and Diebacks
.
Ceratocystis paradoxa
Black Scorch
,
Bud
Scorch
,
Heart Rot
of coconut, Canary, Washing-
ton, and Guadaloupe palms, also causing
a pineapple disease in the tropics. The most strik-
ing symptom is a black, irregular, necrotic con-
dition of the leaf stalk. The tissues look as if they
had been burned, whence the name black scorch.
Furled pinnae of leaf fronds show pale yellow
spots with broad margins that later converge and
turn black; infection spreads rapidly, and in
severe cases the heart leaves dry up. The heart
rot discolors trunk tissues and rots the pithy mate-
rial between cells. Infection is through wounds
during periods of relatively high humidity, or
through roots, or sometimes through uninjured
fruit strands, petioles, or pinnae. Palms with vital-
ity lowered, as when the normal crown of leaves
has been reduced but the water supply to the
leaves is not reduced, are most susceptible.
Control
Destruction of infected parts seems to
be the chief control measure. It is easier to bury
than to burn palm trunks.
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