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Direct damage to the plant occurs when
melon aphid nymphs and adults pierce the
plant tissue and extract sap, resulting
in loss of vigor, stunting, curled leaves,
and reduced yield, and/or plant death.
Indirect damage is caused by deposits
of honeydew (which serves as a substrate
for sooty mold), shed skins and by transmission
of viruses, which are particularly important
in vegetable crops. The melon aphid is
a vector for both nonpersistant and persistently
transmitted viruses.
Nonpersistantly transmitted viruses are
acquired by aphids in just a few seconds
of feeding or probing, require no latency
period, and can be transmitted to another
plant immediately. After only a few minutes
the aphid is no longer ineffective. Foliar
insecticide applications may actually
increase the spread of nonpersistant viruses
by stimulating increased dispersal and
probing by aphids.
Persistent viruses are acquired by aphids
after 10 to 60 minutes of feeding and,
following a 12-hour latency period, aphids
will remain ineffective for up to their
entire life span.
The virus diseases often have distinctive
symptoms and result in reduced growth
and yield. They can cause mottling and
distortion of fruit.
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