Symptoms
Infected leaves often feel sticky, and the sap can be colonised by
black sooty mould.
Bad infestations can leave a plant vulnerable to attack by other
pests and diseases. Virus diseases can be spread by black-fly as
they move from one infected plant to another.
Spot them
Part of the aphid family, black-fly are about 2mm long, black,
round and full of sap.