Biology Reference
In-Depth Information
Galls
Galls are local swellings, hyperplastic enlarge-
ments of plant tissue due to stimulation from
insects, bacteria, fungi, viruses, and occasionally
physiological factors. Crown gall, a common and
serious problem, is discussed under Bacterial
Diseases. Cedar galls are treated under Rusts.
See
exposing the spore-bearing layer. There is sel-
dom more than one diseased shoot on a stem,
and not many on the whole bush; so the disease
does not cause serious damage.
Control
Handpicking of affected parts,
searching carefully for diseased leaves at base
of new growth, removing them before spores
are formed, keeps sporadic infection at
a minimum. Spraying with a low-lime bordeaux
may be effective but is seldom necessary.
Exobasidium oxycocci
Cranberry Rose Bloom
,
Shoot Hypertrophy
on cranberry, and manza-
nita. The disease appears in cranberry bogs soon
after water is removed in spring. Bud infection
results in abnormal lateral shoots with enlarged,
swollen, pink or light rose distorted leaves that
somewhat resemble flowers. Excessive water
supply promotes the disease. Remove water
early in spring. If necessary, spray with bordeaux
mixture.
Exobasidium rhododendri
Rhododendron
Leaf Gall
. Large vesicular galls, especially on
Rhododendron catawbiense
and
R. maximum
.
Exobasidium symploci
Bud Gall
on sweetleaf.
Exobasidium uvae-ursi
Shoot Hypertrophy
of
bearberry.
Exobasidium vaccinii
Azalea Leaf Gall
,
Red
Leaf Spot
,
Shoot Hypertrophy
of and romeda,
arbutus (
A. menziesii
), bearberry, blueberry (fruit
green spot), box sandmyrtle, chamaedaphne,
cranberry, farkleberry, huckleberry, ledum,
leucotho¨, manzanita, and rhododendron. On
azaleas and other ornamentals the galls are blad-
der-shaped enlargements of all or part of a leaf,
Black Knot
for hypertrophy of plum
▶
branches.
Exobasidium
Basidiomycetes, Exobasidiales
Mycelium intercellular with branched haustoria
entering host cells; basidia extend above the layer
of epidermal cells much like the layer of asci in
Taphrina
; each basidium bears two to eight
basidiospores. Species cause marked hypertro-
phy in the Ericaceae.
Exobasidium vaccinii
Leaf Gall
, widespread on
flame azalea.
Exobasidium burtii
Leaf Gall
,
Yellow Leaf
Spot
on azalea and rhododendron.
Exobasidium camelliae
Camellia Leaf Gall
on
camellia in the Southeast, more common on
sasanqua than on japonica. Symptoms are
a striking enlargement and thickening of leaves
and a thickening of stems of new shoots. Dis-
eased leaves are four or more times as wide and
long as normal leaves, very thick and succulent.
Color of the upper surface is nearly normal, but
the underside is white with a thin membrane that
cracks and peels back in strips or patches
