Aphids
Symptoms
The foliage may become yellow and drop off leaving a sticky honeydew remains. The honeydew is actually aphid excrement and looks unattractive, attracts ants and encourages the growth of sooty mould. Ants may be visible on the affected area.
Some species of ants “farm” aphids, protecting them on the plant they eat, and eating the honeydew that the aphids produce.

