Agriculture Reference
In-Depth Information
Fig 5.56 Bunchy top disease showing dark green streaks in the leaf
petiole.
Fig 5.58
Banana streak virus
can be caused by a number of related
viruses.
Fig 5.57 Bunchy top disease on a banana leaf. A 'dot dash' pattern is
seen in the dark green flecks along the veins, connecting with the
midribs of the leaves.
Importance
Banana streak is generally of minor importance in
Lady finger and Cavendish cultivars in Queensland.
However, it is a more serious issue in many newly
developed hybrid cultivars. In many of these, the viral
genome becomes incorporated into the banana plant
genome. Here it is carried latently, and activated later to
produce infections during the breeding and tissue culture
process. From here, the virus spreads, as usual, in planting
material and by mealybugs.
BANANA STREAK
■
Cause
A number of related banana streak viruses (Badnaviruses)
cause banana streak disease.
Symptoms
Disease symptoms and severity are variable and can
disappear and reappear over time. The most common leaf
symptoms are chlorotic and necrotic streaks, which run
parallel to the leaf veins. Less common symptoms can
include stunting, splitting of the outer leaf sheaths of the
pseudostem, cigar leaf and internal necrosis and partial
emergence of bunches.
Management
•
Use planting material only from a plantation that is free
from banana streak, or plants from tissue culture
screened for freedom from banana streak viruses.
Observe quarantine restrictions on the movement of
banana plants within Queensland. Permits are required
before planting bananas.
•
Source of infection and spread
The primary means of spread is in infected planting
material, both conventional bits and suckers, and in tissue
culture. A number of mealybug species can also transmit
the virus from plant to plant, but the rate of spread appears
to be very low in north Queensland at least.
INFECTIOUS CHLOROSIS
■
Cause
Cucumber mosaic virus
(Cucumovirus) .
