Agriculture Reference
In-Depth Information
YELLOW CRINKLE AND MOSAIC
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Cause
Both yellow crinkle and mosaic are caused by the
phytoplasma
Candidatus
Phytoplasma australasia .
Symptoms
The first symptoms of yellow crinkle are a pronounced
yellowing of some leaves, about half-way up the canopy,
giving plants a yellow ring appearance. The leafstalks bend
down where they joint the trunk. The crown leaves develop
thin, translucent areas along the margins and between the
main veins. These areas break away, giving the leaves a
ragged appearance. The crown leaves eventually become
claw-like in appearance and the older leaves dry and fall,
leaving the tree a bare stem with a few stunted leaves at the
top. Plants may remain in this condition for many months,
making no growth and eventually dying.
Fig 14.7 Papaya dieback causing death in new crown leaves.
Fig 14.8 Advanced symptoms of papaya dieback.
Ratoon plants by cutting 75 cm above ground level as
symptoms develop. This results in healthy side shoots and
can save many plants in a plantation. These side shoots are
generally free from detectable phytoplasma, although the
plants are susceptible to further dieback infection.
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Other management options are protecting plants with
insect netting and applying systemic insecticides to
protect plants during times of expected dieback activity.
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Fig 14.9 Papaya crown with yellow crinkle infection. Note the green,
distorted flowers.
