Pests of Specific Crops

Pest Description
Blister Spot (Pseudomonas syringae pv. papulans):
Occurs on ‘Mutsu’ and ‘Fuji’. Light spotting on
‘Jonagold’. Spots on fruit start as small, green,
water-soaked blisters, which later darken and
expand to 4-5 mm in diameter. Leaves may
exhibit a mid-vein necrosis and be curled and
puckered; or have white to brown spots.
Bacteria spread in water and overwinter in
buds, leaf scars and fallen fruit. Fruit are
susceptible to infection for about six weeks,
starting about two weeks after petal fall.
Crown Gall/Hairy Root (Agrobacterium tumefaciens /
Agrobacterium rhizogenes): Large, warty or hairy
growths appear on roots, crowns and stems.
Galls on mature apples can be mistaken for
physiological “burrknots” or wound callus.
The bacteria spread in soil and drainage water
and carry over in soil for many years. M9 and
M26 rootstocks are susceptible to crown gall.
Crown and Root Rot (Phytophthora cactorum): This
soil-borne organism invades crowns of 3- to 10-
year-old trees. Eventually, the trunk is girdled
just below ground level and the tree dies. First
indication of infection may be off-colour foliage
in late summer. The problem is most serious on
irrigated land in the Okanagan.
European Canker (Nectria galligena): Causes severe
damage to apple and pear trees at the Coast.
Twigs and branches wilt and die back above
cankers. First-year cankers have blistered,
yellowish bark. Second-year cankers develop
deeply sunken edges with concentric rings.
Red fungal bodies (perithecia) may be visible at
the edge of cankers in fall. Most infections
occur through leaf scars during fall rains but
infections can occur whenever wounding and
rainfall or irrigation coincide.
Fire Blight (Erwinia amylovora): M9 or M26 rootstock
combined with ‘Braeburn’, ‘Fuji’ or ‘Gala’ are
particularly susceptible to crown infection,
although it can also occur with other rootstocks.
Perennial Canker (Cryptosporiopsis perennans): Fungal
cankers consist of overlapping concentric rings
of woody tissue. Each year the canker enlarges,
gradually girdling the limb or trunk. This
disease is common in the Okanagan but rare in
Coastal areas. Causes “bull’s-eye” rot on fruit.
Very similar to anthracnose.
Chemical Control
(rate per 100 L water; or per
unit area if indicated)
ALIETTE WDG: 2.5 kg/ha
Start at petal fall and repeat at 7
day intervals. Maximum 3
applications per year; no more
than 10 kg/ha before harvest.
BORDEAUX MIXTURE: 100 g
COPPER 53W + 600 g
HYDRATED LIME
Start applying 10 days after calyx
and repeat at 10 day intervals.
Do not apply either product
within 30 days of harvest.
No effective chemical control.
DYGALL (A. radiobacter) root dip
is not registered for use on
apples because it has been shown
to be generally ineffective in
preventing infection of this crop.
Orchards - foliar or drench:
ALIETTE WDG: Rate varies with
tree density. Read label carefully.
Drench:
RIDOMIL GOLD: 1 mL/5 L of
water/tree
In Coastal areas, BORDEAUX
MIXTURE as for fire blight,
applied twice at leaf fall, may
help reduce spread of cankers.
Cultural Management
The disease is worse in
years when very wet
weather occurs while
green fruit are sizing.
Follow good pruning and
tree care practices;
disinfect pruners between
cuts. Remove fallen
(windfall) fruit and bury
or compost.
See General Disease
Management: Crown Gall,
Chapter 9.
Nursery stock should be
planted in disease-free soil.
For propagation, avoid
soils and irrigation water
with a history of crown rot.
M4, M9 and and M26, and
M2 to a lesser extent, are
more resistant than other
commonly-used rootstocks.
The disease is worse in
very wet years. Prune out
infected branches below
cankers and burn or bury.
The fungus can continue
to produce spores on dead
wood.
Nurseries: Destroy
infected trees. Old infected
apple and pear trees near
the nursery should also be
destroyed.
See General Disease Management: Fire Blight, Chapter 9.
Bull’s eye fruit rot:
CAPTAN 50-WP: 6 kg/ha
CAPTAN 80-WP: 3.75 kg/ha
MAESTRO 80DF: 3.75 kg/ha
Cankers:
Research suggests fungicides are
generally ineffective in
preventing spread of cankers. No
fungicides are specifically
registered.
Control the woolly apple
aphid that can spread the
disease. Prune out cankers
whenever possible.
Nursery Production Guide Pests of Specific Crops • 21