Though they look like tiny white flies or moths theses little sap suckers are a relative of aphids and mealy bugs.   You know whitefly has moved into your patch when you are greeted with a cloud of white each time you water or disturb your plants.  Whitefly like company so if you have one you have hundreds or even thousands!

There are around 20 different species of Whitefly in Australia but the two most common species found in both home gardens are:

•   the greenhouse whitefly (Trialeurodes vaporariorum)

•   the silverleaf whitefly (Bemisia tabaci).

Both species look almost identical, but the silverleaf variety is a slightly smaller and a little more yellow in colour than the greenhouse whitefly.

Whitefly are sap sucking insects that attack a wide range of plants, including your veggie crops. And can these little sap suckers leave a trail of damage behind?  Whitefly reproduce rapidly by laying eggs on the underside of leaves.  Both the adult and nymph form of whitefly feed on leaf, bud and stem sap. Affected plant parts turn yellow and streaky. Leaves can curl and wilt which affects plant growth. Whitefly can also spread viruses from plant to plant as they feed.

Whitefly also excrete honeydew which can lead to infestations of sooty mould, a fungal disease that looks like black charcoal on the leaf.  The saliva of the silverleaf whitefly contains a toxin that may cause further damage to the plant.

White fly are most prevalent in late spring and early summer but numbers will naturally decline in the cold of winter. However in warmer climates they are present throughout the year.

Controlling Whitefly

Whitefly are prolific breeders with a short lifecycle.  Eradication of heavy infestations can be a challenge, but employing a combination of control methods to reduce numbers in the short term will lessen plant damage.

  • Yellow Sticky traps – Whitefly are attracted to the colour yellow so by hanging yellow sticky traps near your affected plants will help control their populations.  You can purchase yellow traps from nurseries and garden suppliers or you can make your own at home using laminated yellow paper or plastic smeared with a sticky substance like Paraffin Oil or Vaseline. You need about one trap in every 3m x 3m area.  Make sure you regularly disturb affected plants so the Whitefly swarm and fly into the traps.  BUT BEWARE!  These traps also attract beneficial insects so are NOT the method of choice!
  • Get the dust buster out and vacuum!  Probably only effective at controlling small numbers and make sure you use low suction so your vac won’t damage the plant you’re trying to protect.  Empty the dust bag contents into a labelled plastic bag and freeze before you discard to ensure the captured bugs don’t head back into the garden. Yes, its fiddly and slightly eccentric but may be worth experimenting with!
  • Hosing off and/or constant disturbance for 3 or more days in a row.  Shake, rattle and hose those plants to annoy your unwanted guests.  The idea is to cause enough disturbances to encourage whitefly to move on from your plants.  Again probably only effective in controlling small numbers and unfortunately may not make you popular with your neighbours who are now hosting your whitefly problem!!
  • Attract natural predators such as Ladybirds, lacewings and hoverflies.  These beneficial insects will all devour whitefly nymph and adult whitefly.  Attract these beneficial insects to your garden by planting companion plants like marigolds and alyssum near your precious vegie crops. And don’t use chemical sprays that will also kill these good insects.
  • Home made or commercial organic  natural sprays – Soap, botanical oils or even garlic and chilli sprays may deter Whitefly by adding another line of defence to your arsenal.   However to be effective they need to come in contact with the insect which is difficult when they are airborne!  However the nymphs are more vulnerable as they are on the undersides of leaves so this is where you need to direct your spray mist.

In enclosed greenhouse situations, infestations of whitefly can be controlled by using exclusion netting in doorways or by introducing the predatory wasps Encarsia formosa.  They are available from a number of commercial suppliers.