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Aphids - the ultimate vector
Aphids damage cucurbits in three ways:
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by direct feeding,
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by contamination with excrements, and
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as vectors of viruses.
Aphids insert needle-sized sylets through the skin
to feed on phloem in the underlying tissue.
Infection is immediate - a few seconds of probing is
all that's needed to acquire the virus. This
vector-aphid relationship is called non-persistent
and is characteristic of ZYMV, WMV-2, PRSV and CMV.
The aphid's probing results in damage from the
removal of photosynthate needed to fill developing
fruits. Aphids also feed on the lower surfaces of
the leaf, causing a downward cupping of the leaf.
This cupping forms a protected area in which aphids
can continue to feed and reproduce because
insecticides can't penetrate the cupping areas.
Three aphid species colonize cucurbits and can cause
damage:
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the melon aphid, Aphis gossypii,
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the green peach aphid, Myzys persicae, and
the cowpea aphid, Aphis craccivora.
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