Biology Reference
In-Depth Information
portion visibly blighted. If lesions appear on large
limbs they may be painted with one of the fol-
lowing mixtures:
I. 1 quart denatured alcohol, 1/4 pint distilled
water, 3/4 ounce muriatic acid, 1 1/2 pounds
zinc chloride.
II. 100 grams cobalt nitrate, 50 cc glycerine,
100 cc oil of wintergreen, 50 cc acetic acid,
80 cc denatured alcohol.
III. 5 parts cadmium sulfate stock solution
(1 pound stirred into 2 pints warm water),
2 parts glycerine, 2 parts muriatic acid,
5 parts denatured alcohol.
Formulas I and II were developed for use on
the West Coast, III for New York. The paint is
brushed on the unbroken bark over the lesions
and for several inches above and below the can-
ker; it may injure if there are wounds or cuts.
In cutting out cankered limbs during the dor-
mant season, take the branch off at least 4
inches back from edge of the canker, and
disinfect the cut. The home gardener may want
to use 10 % Chlorox for tools and bordeaux paint
for cut surfaces. Dry bordeaux powder is stirred
into raw linseed oil until a workable paste is
formed.
Almost all desirable pear varieties are suscep-
tible to fire blight, particularly Bartlett, Flemish
Beauty, Howell, Clapps Favorite. Varieties Old
Home, Orient, and the common Kieffer are more
or less resistant. Jonathon apples are very suscep-
tible. Less apt to be severely blighted are
Baldwin, Ben Davis, Delicious, Duchess, McIn-
tosh, Northern Spy, Stayman, and Winter
Banana. At the University of California some
work has been done on susceptibility of ornamen-
tals to fire blight.
Pyracantha angustifolia
is quite
susceptible, but
P. coccinea
and
P. crenulata
are
rather resistant.
Cotoneaster salicifolia
is suscep-
tible;
C. dammeri, C. pannosa
, and
C.
horizontalis
are more resistant; and
C. adpressa
and
C. microphylla
show marked resistance.
Cultural methods influence the degree of fire
blight, which is worse on fast-growing succulent
tissue. Avoid heavy applications of nitrogen fer-
tilizers; apply such nitrogen as is required in
autumn or in spring in foliar sprays after danger
of blossom blight is over.
Erwinia carnegieana
Bacterial Necrosis
of
giant cactus in the entire habitat of
Carnegia
gigantea
. Long present in southern Arizona, this
disease was not described until 1942, after it had
encroached on cactus parks and private estates.
Many giant cacti in the Saguaro National Monu-
ment have been killed, with heaviest mortality in
trees 150 to 200 years old.
Symptoms start with a small, circular, light
spot, usually with a water-soaked margin. The
tissues underneath turn nearly black; the spot
enlarges and has a purplish hue with the center
cracking and bleeding a brown liquid. The rotten
tissues dry, break up into granular or lumpy
pieces, and fall to the ground. Rotting on one
side means leaning to that side; when the trunk
is girdled near the base, the giant is likely to fall in
a wind-storm. If it does not break, it stands as
a bare, woody skeleton, with all parenchyma
tissue disintegrated. An insect,
Cactobrosis
fernaldialis
, is largely responsible for the rapid
spread of the disease. The larvae tunnel inside the
stems most of the year, emerging from May to
August to pupate for a month or so before the
adult, a tan and brown nocturnal moth, lays eggs.
Control
A phosphate dust, applied monthly from
April to September, has effectively controlled the
insect vector. Incipient infections can be cut out
and the cavity allowed to dry out and cork over.
Before the insect vector was known, fallen trees
were cut into short lengths, dragged to a burial
pit, covered with a disinfectant, and then with
soil.
Erwinia carotovora subsp. carotovora (for-
merly
Erwinia carotovora
).
Soft Rot
of calla,
originally described from common calla, found
on golden calla, and also on beet, cactus, cab-
bage, cauliflower, celery, cucumber, carrot, egg-
plant, geranium (
Pelargonium
), hyacinth, iris,
onion, parsnip, pepper, potato, salsify, sansevie-
ria, tobacco, tomato, and turnip.
On calla lily the soft rot starts in upper portion
of the corm and progresses upward into leaf and
flower stalks or down into roots, with the corm
becoming soft, brown, and watery. Sometimes
infection starts at edge of petiole, which turns
slimy. Leaves with brown spots and margins die
or rot off at the base before losing color. Flowers
