PROTECTING PLANTS FROM THINGS THAT PREY ON THEM - Continued
Pear diseases.--Fire-blight kills the twigs and branches, on which the
leaves suddenly blacken and die but do not fall. It also produces
cankers on the trunk and large limbs. Prune out blighted branches as
soon as discovered, cutting 6 to 8 in. below the lowest evidences of the
disease. Clean out limb and body cankers. Disinfect all large wounds
with corrosive sublimate solution, 1 to 1000, and cover with coat of
paint. Avoid forcing a rapid, succulent growth. Plant the varieties
least affected.
Pear scab is very similar to apple scab. It is very destructive to some
varieties, as, for example, Flemish Beauty and Seckel. Spray three times
with bordeaux, as for apple scab.
Plum and cherry diseases.--Black-knot is a fungus, the spores of which
are carried from tree to tree by the wind and thus spread the infection.
Cut out and burn all knots as soon as discovered. See that the knots are
removed from all plum and cherry trees in the neighborhood.
Leaf-spot is a disease in which the leaves become covered with reddish
or brown spots and fall prematurely (Fig. 211); badly affected trees
winterkill. Often, the dead spots drop out, leaving clear-cut holes.
Spray with bordeaux, 5-5-50. For cherries, make four applications:
first, just before blossoms open; second, when fruit is free from calyx;
third, two weeks later; fourth, two weeks after third. In plums it may
be controlled by two or three applications of bordeaux, 5-5-50. Make the
first one about ten days after the blossoms fall and the others at
intervals of about three weeks. This applies to European varieties.
Japan plums should not be sprayed with bordeaux.
Potato diseases.--There are different kinds of potato blight and rot.
The most important are early blight and late blight--both fungous
diseases. Early blight affects only the foliage. Late blight kills the
foliage and often rots the tubers. Two serious troubles often mistaken
for blight are: (1) Tip burn, the browning of the tips and margins of
the leaves due to dry weather; and (2) flea-beetle injury, in which the
leaves show numerous small holes and then dry up. The loss from blight
and flea-beetles is enormous--often, one-fourth to one-half the crop.
For blight-rot and flea-beetles spray with bordeaux, 5-5-50. Begin when
the plants are 6 to 8 in. high and repeat every 10 to 14 days during the
season, making 5 to 7 applications in all. Use 40 to 100 gal. per acre
at each application. Under conditions exceptionally favorable to blight
it will pay to spray as often as once a week.
Scab is caused by a fungus that attacks the surface of the tubers. It is
carried over on diseased tubers and in the soil. In general, when land
becomes badly infested with scab, it is best to plant it with other
crops for several years. (See page 190.)
Raspberry diseases.--Anthracnose is very destructive to black
raspberries, but not often injurious to the red varieties. It is
detected by the circular or elliptical gray scab-like spots on the
canes. Avoid taking young plants from diseased plantations. Remove all
old canes and badly diseased new ones as soon as the fruit is gathered.
Although spraying with bordeaux, 5-5-50, will control the malady, the
treatment may not be profitable. If spraying seems advisable, make the
first application when the new canes are 6 to 8 in. high and follow with
two more at intervals of 10 to 14 days.
Cane-blight or wilt is a destructive disease affecting both red and
black varieties. Fruiting canes suddenly wilt and die. It is caused by a
fungus which attacks the cane at some point and kills the bark and wood,
thereby causing the parts above to die. No successful treatment is
known. In making new settings, use only plants from healthy plantations.
Remove the fruiting canes as soon as the fruit is gathered.
Red-rust is often serious on black varieties, but does not affect red
ones. It is the same as red rust of blackberry. Dig up and destroy
affected plants.
Rose diseases.--Black leaf-spot is one of the commonest diseases of
the rose. It causes the leaves to fall prematurely. Spray with bordeaux,
5-5-50, beginning as soon as the first spots appear on the leaves. Two
or three applications at intervals of ten days will very largely control
the disease. Ammoniacal copper carbonate may be used on roses grown
under glass. Apply once a week until disease is under control.
For mildew on greenhouse roses, keep the steam pipes painted with a
paste made of equal parts lime and sulfur mixed up with water. The
mildew is a surface-feeding fungus and is killed by the fumes of the
sulfur. Outdoor roses that become infested with the mildew may be dusted
with sulfur, or sprayed with a solution of potassium sulfide, 1 oz. to 3
gal. water. Spray or dust with the sulfur two or three times at
intervals of a week or ten days.
Strawberry leaf-spot.--The most common and serious fungous disease of
the strawberry; also called rust and leaf-blight. The leaves show spots
which at first are of a deep purple color, but later enlarge and the
center becomes gray or nearly white. The fungus passes the winter in the
old diseased leaves that fall to the ground. In setting new plantations,
remove all diseased leaves from the plants before they are taken to the
field. Soon after growth begins, spray the newly set plants with
bordeaux, 5-5-50. Make three or four additional sprayings during the
season. The following spring, spray just before blossoming and again 10
to 14 days later. If the bed is to be fruited a second time, mow the
plants and burn over the beds as soon as the fruit is gathered. Plant
resistant varieties.
Tomato leaf-spot.--The distinguishing character of this disease is
that it begins on the lower leaves and works towards the top, killing
the foliage as it goes. It is controlled with difficulty because it is
carried over winter in the diseased leaves and tops that fall to the
ground. When setting out plants, pinch off all the lower leaves that
touch the ground; also any leaves that show suspicious-looking
dead-spots. The trouble often starts in the seed-bed. Spray plants very
thoroughly with bordeaux, 5-5-50, beginning as soon as the plants are
set out. Stake and tie up for greater convenience in spraying. Spray
under side of the leaves. Spray every week or ten days.