Agriculture Reference
In-Depth Information
Fig 18.10 Colletotrichum crown rot developing around the stolon's
point of attachment.
Fig 18.12 Leaf spots caused by Colletotrichum. Note that the spots
have diffuse margins.
Crown infection probably occurs through old fruit
stems, stolons and petioles. Cultivars differ in their
susceptibility to crown rot. Transplants grown in
Queensland are more prone to the disease than those
from other sources.
Importance
While significant losses have occurred in some fruit crops
in recent years, the overall problem is small.
Fig 18.11 Colletotrichum crown rot showing a section through the
crown and stolon.
Management
•
black sunken lesions may develop on stolons and petioles.
Lesions on stolons expand rapidly, girdling the stolon
and killing the unrooted young runners. Round, black,
water-soaked spots up to 5 mm in diameter may occur
on leaves.
Monitor runner production beds for the disease, apply
appropriate fungicides and use nitrogen fertilisers
judiciously.
Remove and destroy affected plants in runner beds.
•
Plant healthy runners obtained from an accredited source
into fruit-production areas.
•
Source of infection and spread
Planting infected runners is a major means of spread. The
origin of the initial fungal inoculum unknown but it is
probably distributed widely at low levels in strawberry fruit
crops and runner-production beds. The fungus may also
survive on alternative weed and crop hosts.
Colletotrichum
lives on both green and dying strawberry tissue. Spores are
blown or water splashed to other plants. The pathogen
spreads quickly in wet conditions, with warm to hot
weather favouring the disease.
Maintain regular fungicide sprays.
•
CROWN ROT
■
Cause
Several pathogens are commonly associated with crown rot.
The most common are
Fusarium oxysporum
,
Phytophthora
