Aphids - Symptoms and how to get rid of them!

What are Aphids?

Commonly known as Blackfly or Greenfly, aphids are small soft-bodied insects ranging in size from 0.5mm to about 6.5mm in length.  Colours can vary between different species and even between strains of the same species, ranging from shades of green through to black, yellow, chestnut brown, pink, grey and waxy white.  Several species have darker markings on a lighter toned body, camouflaging them against their plant background.  Winged (alate) aphids are frequently produced in response to adverse conditions such as overcrowding, poor plant condition, the onset of winter conditions or for migratory purposes.

Ants are frequently associated with aphids and may be assumed to be feeding on the insect when they are in fact feeding on the sugary honeydew and will defend aphids from attack by predators.  Ants therefore need to be managed to gain control of the aphids.

Symptoms of Aphids

Common Name: Blackfly, greenfly, plant lice
Scientific name: aphids
Plants affected: majority of plants, usually soft new growth.
Main symptoms: various; leaf distortion, leaf yellowing, sticky upper-surface of leaves, white skins on upper-surface of leaves and possible black sooty mould from sticky honeydew produced by aphids
Most Active: all year round at 10C up to 35C, if temperature is lower they may enter diapause (a type of hibernation for insects and mites).

How to control Aphids

Non-chemical control:

Includes naturally occurring parasitoid wasps, hoverflies, ladybirds and other predatory insects. While predators include Aphidoletes aphidimyza, green lacewing larvae Chrysoperla carnea, two spotted ladybird Adalia bipunctata and hoverfly species.   

Chemical control:

Physically acting contact sprays such as SB Invigorator for treatment of a wide range of small insect and mite pests.  It is formulated as a long chain molecule which effectively smothers and suffocates the target organism.  More actively mobile insects and mites such as predators and parasitoids can easily break the surface tension of the spray allowing them to survive and continue attacking the pests.

Written by: Neil Helyer, IPM Specialist, Fargro Ltd.