Aphids
Why Are They a Problem?
Aphids can build up their populations quickly. These populations generally extract sap from plants. Aphids damage plants by sucking the sap from various plants in the garden and on your houseplants. Because aphids suck out great quantities of sap from plants and do so in such large groups, leaves and stems will become distorted. Leaves attacked by aphids can also have yellow discolouration, usually on the undersides. The leaves may later dry out, curl or wilt.
Aphids excrete excess plant sap — known as honeydew — which can make the affected plants sticky.
In addition, certain types of ants prefer to eat this honeydew, and will ‘farm’ whole colonies of aphids to collect the honeydew that they excrete. In addition, the excreted honeydew can make plants, sidewalks, car and patio furniture, wet and sticky. A sooty mould often grows in the honeydew that blackens stems, leaves and any other surface.
Aphids may also transmit plant pathogens.
Aphid Biology
Aphids (also known as “plant lice”) are pear-shaped insects that may be green, black, yellow, brown, red, pink, or white. They are slow moving and range in size from one to three millimetres in length. They have conspicuous slender antennae and near the rear end of the abdomen there are two tubes called cornicles. Some species exude a wax from their cornicles that paralyzes the attacker and some species also have transparent wings. The female is capable of parthenogenesis, which means she can produce young without mating, up to 25 daughters in a day.
How to Prevent Invasions & Infestations
- Avoid heavy applications of nitrogen fertilizer, which can encourage succulent plant growth.
- Wash away any aphids with a steady stream of water or rub them off by hand: focus on the underside of leaves and on the youngest parts of the plant.
- Introduce natural predators such as ladybugs and Aphid lions to feed on the aphids — they may not always provide adequate control.
Recommended Treatment
Aphids excrete excess sap, which certain ants prefer to eat. If aphids have an ant ‘farmer’ to keep predators at bay, the aphid population can swiftly become a problem in the garden. If the infestation is severe and the prevention tips do not help, use one of the federally registered insecticides listed below.