Agriculture Reference
In-Depth Information
Management
•
Importance
Yellow speckle is one of several viroid and virus diseases
infecting grapevines in Australia. The pathogens affect
vine vigour, yields and fruit quality.
Use clean planting material, including hot water
treatment of stock, before movement and planting.
Use rootstocks resistant to root-knot nematodes.
•
Use cultural practices to reduce nematode populations
before planting.
•
Management
•
Establish new plantings using virus and viroid-free
propagating material from an approved source.
Fumigate the soil before planting.
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VIRUSES/VIROIDS
LEAFROLL
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Cause
Grapevine leafroll virus
.
GRAPEVINE YELLOW SPECKLE
■
Cause
Grapevine yellow speckle viroids.
Symptoms
Infected plants do not show symptoms for most of the year.
Early autumn colours are the first signs of the disease and
these usually appear on mature leaves near the base of
shoots and later on younger leaves. Symptoms are more
distinct in cooler seasons and on the shaded sides of vines.
In most varieties, margins of affected leaves curl or roll
down.
Symptoms
Tiny, irregular yellow speckles, ranging in size from
pin-point to about one millimetre, develop on exposed
mature leaves. The symptoms occur along the main veins
and veinlets and may be isolated or clumped. The speckles
are at first yellow-green and then turn yellow or white-
yellow later in the season.
Leaves of infected red fruit varieties turn red to purple
between the veins while the leaf tissue adjacent to the
main veins usually remains green.
The symptoms usually appear on only a few leaves on a vine.
Leaves of white-fruited varieties turn yellow between the veins.
Source of infection and spread
The viroids involved are transmitted by grafting, so infected
propagation material is the major source of new infections.
On severely affected leaves, some of the red or yellow-
coloured areas may die.
Fig 9.31 Yellow speckle disease. Yellow vein banding and speckling
occurs on leaves.
Fig 9.32 Leafroll virus. Affected vines have red leaves with
characteristic dark green veins.
