Agriculture Reference
In-Depth Information
18
STRAWBERRY
(
Fragaria
×
ananassa
)
Fresh strawberries are among the most popular fruit in
Australia. The strawberry plant (
Fragaria
usually die. Runners from infected plants also show
symptoms.
Strawberry green petal (broccolberry): infected plants
produce f flowers where green, leaf-like structures replace
the normal petals and fruit look like heads of mini broccoli.
ananassa
) is a
member of the Rosaceae family, with its origin in Europe.
×
It is propagated by planting stolons (runners), which, in
commercial practice, are produced by specialist growers.
Although strawberries are grown in many cooler areas of
Australia, commercial production is concentrated north
of Brisbane in Queensland and at several locations in
Victoria.
TBB: this disease is similar to green petal disease but
without the broccolberry symptom.
Source of infection and spread
The pathogens are transmitted to strawberry plants by
leaf hoppers, after they have fed on infected alternative
hosts. Symptoms develop in infected strawberry plants
six to eight weeks after infection. This means that
lethal yellows symptoms appear after the runners are
harvested and planted into fruit production beds. There
is little spread of lethal yellows between strawberry
plants.
The varieties used are from breeding programs in Australia
and introductions from other countries, notably the United
States.
Planting healthy runners is vital for disease control while
fruit rots can cause considerable losses if prolonged wet
weather occurs during fruiting.
BACTERIA AND
PHYTOPLASMAS
The rickettsia infection is more common in southern
Queensland. The disease associated with
Candidatus
Phytoplasma australiense occurs in other states and local
infections are common in south-eastern Queensland.
LETHAL YELLOWS AND GREEN PETAL
■
Importance
Once thought to be minor, lethal yellows have caused large
losses in runner-production areas and uncertainty, in some
years, in the health of transplants sent to fruit-production
farms.
Cause
The phytoplasma,
Candidatus
Phytoplasma australiense,
is responsible for lethal yellows and the strawberry
green petal disease. A rickettsia-like organism is also
associated with the lethal yellows disease. The tomato
big bud (TBB) phytoplasma (
Candidatus
Phytoplasma
australasia) is also responsible for big bud/green petal
symptoms.
Management
•
Remove infected plants and attached runners in runner
beds.
Symptoms
Lethal yellows: infected plants show some inward rolling
and purpling of older leaves, which f flatten to the ground.
Young leaves develop yellow margins and remain small with
short leaf stalks, causing clusters of small, yellow-fringed
leaves in the centre of the plant. Plants become stunted and
Plant runners from approved or certifi ed runner
schemes.
•
Control weeds around strawberry blocks.
•
Use appropriate chemicals for controlling leafhoppers
in runner production areas.
•
