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Plum Pockets
This fungal disease caused by Taphrina communis is
common on plants grown in
Saskatchewan.
SYMPTOMS
This disease affects the leaves, shoots and fruits. Symptoms on
fruit are visible soon after
fruit set. The fruit becomes very large, sometimes ten times
normal plum size, hollow
(without pits) and bladder like. They are yellow at the start
but soon turn red and later
powdery grey. Affected twigs are swollen and distorted, and
affected leaves are malformed
and curled.
DISEASE CYCLE
The fungus overwinters on infected twigs and buds and the disease
is spread by spores in the
spring shortly after the blossom buds open. Cool, wet conditions
during this period are
necessary for infection.
CONTROL
- Prune back infected branches and burn these along with any
other affected fruits and twigs
that can be gathered. This will eliminate much of the source of
inoculum. Large pruning
wounds should be covered with a wound dressing such as Braco,
shellac or other reliable
wound dressing product available from seed and garden supply
dealers.
- In addition to pruning, a dormant spray with a fungicide will
help control plum pockets. Use
one of the following sprays: 2 tablespoons per gallon of thiram,
or a lime-sulfur solution (1
part lime-sulfur to 9 parts water) or 8:8:100 Bordeaux mixture
(see below). The timing of
the application is important to get effective control and not
damage the plants. Spraying
should be done just before the buds open. When the
flower buds are at the popcorn stage
and again just after the petals fall, a spray with lime-surfur at
4 pounds in 100 gallons or
wettable sulfur at 4 pounds in 100 gallons, have also been
recommended. When using
chemical control read the product label carefully and follow
directions on use and on
handling precautions.
Bordeaux Mixture - A small volume of 8:8:100
Bordeaux mixture is made by dissolving 4
ounces of copper sulfate (Bluestone or Blue Vitriol) in one
gallon of water and 4 ounces of
calcium hydroxide (hydrated or slaked lime) in 2 gallons of
water. Pour the copper sulphate
solution into the lime water and strain through fine cheesecloth.
Use the solution
immediately after mixing and also, fresh lime solution is
essential, not some left over from
the previous season.
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