Biology Reference
In-Depth Information
Fig. 2
Cedar-Apple Rust.
Gymnosporangium
juniperi-virginianae
. a
section through crabapple
leaf with pycnidia (
0
)on
upper surface and aecium
(
I
) with prominent
peridium and aeciospores
in chains on undersurface;
b two-celled teliospores on
gelatinous stalks, which
help form the jellylike telial
horns on cedar galls; c,
teliospores germinating
with a promycelium and
basidiospores; d teliospore
of
G. clavipes
, the quince
rust
leaves, fruit of hawthorn. Telia are 3 to 4 mm high
on irregular galls on cedar twigs and branches.
Gymnosporangium biseptatum III on stems of
Chamaecyparis thyoides
; 0, I on amelanchier.
Spindle-shaped swelling in stem; trees may die.
Gymnosporangium clavariiforme III on com-
mon and Mountain juniper; 0, I on chokeberry,
amelanchier, pear and quince. Slender telia 5 to
10 mm high produced on long fusiform swellings
on branches.
Gymnosporangium clavipes
Quince Rust
. III
on eastern red-cedar, dwarf, mountain, and pros-
trate junipers; 0, I on fruits and young stems of
amelanchier, apple, chokeberry, crabapple, haw-
thorn, mountain-ash, quince, Japanese quince and
pear. Short slight swellings, somewhat spindle-
shaped, occur in cedar twigs and branches, many
of which die. On the main trunk, infected areas
are black rough patches or rings around the bark.
Mycelium is perennial, confined to the outer layer
of living bark; it can sometimes be scraped out by
scraping the bark. On pomaceous hosts, the dis-
ease is most frequent on fruits, often causing
distortion. Rust sometimes affects twig and buds
but seldom leaves. Aecia are particularly promi-
nent on hips of English hawthorn, with long whit-
ish perithecium around orange spores.
Control
Some apple varieties susceptible to
apple rust are rather resistant
including Jonathan, Rome, Ben, Davis, and
Wealthy. Red Delicious is quite susceptible.
Destroy cedars in neighborhood of orchards;
spray as for apple rust.
Gymnosporangium confusum III on Savin
Juniper; 0, I on hawthorn.
Gymnosporangium cornutum (
G.
auriantiacum
).
Juniper Gall Rust
. III on
leaves and stems of common juniper; 0, I on
mountain-ash.
Gymnosporangium cunninghamianum III on
Arizona cypress; 0, I on amelanchier.
Gymnosporangium davisii III on mountain
and common juniper; 0, I on leaves of red and
black chokecherry. Telia are usually on upper
surface of needles, sometimes at base of stems.
Gymnosporangium effusum III on eastern red-
cedar; 0, I on chokeberry. Fusiform swellings on
cedar trunk and branches.
Gymnosporangium ellisii
Witches' Broom
Rust
. III on southern white cedar
(
Chamaecyparis
); 0, I on sweet-fern, gale, bay-
berry, wax-myrtle leaves, fruits and young stems.
Aecia are cluster cups; telia are cylindrical, fili-
form, 3 to 6 mm high, appearing on leaf blade or
axil the first season after infection, thereafter only
on stems, invading inner bark and wood.
Witches' broom are abundant; even large trees
die if heavily broomed.
to quince rust,
