Agriculture Reference
In-Depth Information
cussed to maintain healthy trees. Remove all wild and escaped stone fruit
plants from hedgerows, woodlots, and other non-crop areas of your orchard.
Before bud break in the spring and at any other time you find them, prune
out the knots, cutting at least 4 inches below the knots themselves. Burn or
bury the prunings.
Your normal fungicide program, including Bordeaux and lime sulfur
sprays, will help manage black knot, provided you have followed the cultural
steps above. Do not apply sulfur products to apricots. 'Bluefre', 'Damson',
'Shropshire', and 'Stanley' plums are highly susceptible; 'Bradshaw', 'Early
Italian', 'Fellenburg', 'Methley', and 'Milton' plums are somewhat less suscept-
ible. Resistant to highly resistant plum varieties include 'Formosa', 'President',
Santa Rosa', and 'Shiro'.
Peach Leaf Curl and Plum Pocket
Peach leaf curl (
Taphrina deformans
) and plum pocket (
Taphrina commu-
nis
) are peach and plum diseases. Peach leaf curl is widespread and common.
Plum pocket does not infect commercial varieties of European and Asian
plums, but it does infect some species of native plums in North America.
Symptoms.
Peach leaf curl symptoms first appear on expanding leaves in
early spring. The leaves become thick and distorted and may become red-
dish or purplish. Infected leaves eventually become covered with silvery -
gray spores, then drop early. New leaves may form in their place. Blossoms,
young fruit, and shoots can also become infected and young shoots killed.
Defoliation weakens the trees, making them more susceptible to winter in-
jury and other diseases.
Plum pocket symptoms appear on the fruits as small, whitish spots. The
spots enlarge, eventually covering the fruit. The plums become hollow and
enlarge many times their normal size.
The pathogens overwinter as spores in the bud scales and in cracks in the
bark. The spores germinate during cool, wet weather in early spring to infect
