Biology Reference
In-Depth Information
possible with a windbreak in between of some tall
nonsusceptible host. Some states have laws
prohibiting red-cedars within a mile of commercial
apple orchards, but for practical garden purposes
a few hundred yards is sufficient, the danger mark-
edly decreasing with distance, especially with
a house or hedge as a windbreak.
If junipers are already planted, it is possible in
late winter to go over small specimens and
remove galls before spore horns are formed.
Spraying in spring inhibits telial development
and germination of teliospores. Spray red-cedars
in August to prevent infection from crabapples.
Fairly resistant apple varieties are Baldwin,
Delicious, Rhode Island and North-western
Greening, Franklin, Melrose, Red Astrachan,
Stayman, and Transparent. Avoid susceptible
Jonathan, Rome, Wealthy, and York Imperial.
Most junipers susceptible to apple rusts are culti-
vars of
Juniperus virginiana
and
J. scopulorum
.
Many cultivars of
J. chinensis
and
J. horizontalis
are resistant, and there are even some resistant
forms of
J. virginiana.
Gymnosporangium kernianum III on alliga-
tor, Utah, and western junipers; 0, I on
amelanchier and pear. Telia arise between leaves
on green twigs, but mycelium is perennial in
stems, causing dense witches' broom 6 to
18 inches in diameter.
Gymnosporangium libocedri III on incense
cedar; 0, I on leaves, fruits, of amelanchier and
hawthorn, also apple, crabapple, pear, quince, Jap-
anese quince and mountain-ash. Aecium is
a cluster cup on foliage; telia are always on leaves;
witches' broom and swellings are produced on
branches, rarely on trunks. The fungus is said to
persist in the mycelial stage up to 200 years.
Gymnosporangium multiporum III on stems
of western, one -seed, and Utah juniper between
leaves; 0, I unknown.
Gymnosporangium nelsonii III on juniper and
red-cedar; 0, I on leaves of amelanchier.
Gymnosporangium nelsonii III on one-seed,
prostrate, Rocky Mountain, Utah, and western
junipers; 0, I on hawthorn, quince, Oregon crab,
pear, squaw-apple and Pacific mountain-ash.
Galls are firm, woody, round, up to 2 inches in
diameter.
Gymnosporangium nidus-avis
Witches'
BroomRust
. III on eastern and southern red-cedars,
on prostrate and Rocky Mountain junipers; 0, I on
fruit, young stems, leaves of apple, hawthorn,
mountain-ash, quince, Japanese quince,
amelanchier or serviceberry. Trunks and branches
of large trees have witches' broom and long spindle-
shaped swellings. Aecia are on both leaf surfaces.
Gymnosporangium nootkatense
Gall Rust
. II,
III on Alaska cedar; 0, I on mountain-ash, and
Oregon crabapple. This is the only
Gymnosporangium
species with uredial stage.
Uredia are bright orange fading to pale yellow;
teliospores appear later in the same pustules.
Aecia are cluster cups.
Gymnosporangium speciosum III on alligator,
one-seed, and Utah junipers; 0, I on leaves of
syringa (
Philadelphus
) and fendlera. Telia are in
longitudinal rows on long fusiform swellings on
juniper branches, which are girdled and die. In
severe infections the whole tree dies.
Gymnosporangium trachysorum III on stem
of eastern red-cedar; 0, I on hawthorn leaves.
Swellings on cedar are abruptly fusiform to glo-
boid with prominent telia 6 to 10 mm high.
Gymnosporangium tremelloides (
G.
juniperinum
). III, stem gall on mountain juniper;
0, 1 on Pacific mountain-ash. On smaller
branches swellings are subglobose galls up to
3/4 inch in diameter; hemispherical swellings on
larger branches are covered with flattened telia.
Gymnosporangium vauqueliniae
Witches'
Broom Rust
. III on one-seed juniper; 0, I on
Vauquelinia californica
. This rust is the only
Gymnosporangium
causing witches' broom on
the aecial host.
Hyalopsora
Melampsoraceae. Telia on ferns, teliospores sev-
eral-celled, in epidermis; urediospores of two
kinds, with pores.
Hyalopsora aspidiotus
Fir-Fern Rust
.0,Ion
balsam fir; II, III on oak fern (
Phegopteris
dryopteris
). Pycnia are slightly raised orange-
yellow spots on needles; aecia are yellow to
white, columnar, on 2-year needles.
