aphid insects under leaf

Aphid insects are small insects that extract the sap from plants. Depending upon the specie, they measure up to 3mm in size. Aphids are often found on or under leaves, on soft stems or in crevices between leaves.

Despite their status as a pest insect they are quite interesting. For most of the year, most aphid insects are female. These female adults give birth to fully formed female babies. This means they can reproduce extremely rapidly.

In most species of aphids, those newly born females already have fully formed female babies in their wombs. Likewise, in most aphid insect species, males are born at the end of summer to early autumn. In some species of aphids only the males have wings. In other species both males and females have wings.

Sexual reproduction happens at the end of summer to early autumn. She lays eggs. If the eggs successfully overwinter, they hatch females in spring.

Aphids tend to feed in community clusters. They prefer warm weather.

Aphids can transmit diseases from plant to plant and also introduce viruses. However, predatory insects are usually the only necessary element when seeking to control aphids.


Some types of aphids

There are around 150 different types of aphids in Australia. Of them, only about 12 are native. For that reason, we often find aphids on our exotic plants such as our ornamentals and our fruit and vegetable plants.

  1. The cabbage aphid insect is from Europe and grey-green in colour, although some can be quite dark green. She targets brassicas (cabbage, broccoli, Brussels sprouts, cauliflower, turnips etc) causing stunting to younger plants. Severe infestations can cause yellowing, leaf curling and distortion.
  2. Green peach aphid insect is quite common and becoming resistant to many chemical pesticides. In fact, it might be that this aphid is one of the most pesticide resistant insects that we might have in our gardens. Read my blog about the effect of insecticides to find out how using chemicals to kill is creating super bugs resistant to our chemicals. These aphids can be winged or wingless and vary in colour from cream to green to black. The winged aphids tend to be born when the colony is overcrowded. At such times they take to the wing and find other food sources.
  3.  Rose aphids are host specific and only tend to attack roses. They range from greens, to pinks to orange and measure up t 2.5mm in length. Like other species, their eggs hatch in spring. Females hatch and give birth to life young.       Overcrowded colonies disperse by the birth of winged aphid insects.

Controlling aphids naturally

Aphids insects have a number of predators including parasitic wasps, lady beetle and their larvae, lacewings and their larvae, and hover flies and their larvae.

Unless we use a pesticide in our gardens – and this includes natural pesticides such as neem oil or pyrethrum – we are likely to have a good community of predatory insects. If we use pesticides our gardens become resistant to predator insects – that’s not a good thing!

I’ve written a blog and developed a video of aphids and some of their predatorsGood gardeners look and monitor any aphid or other insect infestation before taking action. Most of the time there is one of more species of predator at work and we need to do nothing at all.

A small colony of aphids isn’t usually terminal or serious. Even a large colony isn’t usually a drama unless we make it one! In fact, read my blog on trusting nature to find out how a massive aphid infestation was completely taken care of by predatory insects.

The video below shows how some key predatory insects demolished a mealybug and aphid infestation.


Controlling aphids by prevention

Aphid insects tend to be attracted to sick plants. My blog on susceptible and resistant plants explains, among other things, how plants release metabolites that are communications with others such as insects.

A sick plant releases a different metabolite compared to a healthy plant. Sick plants tend to attract sap sucking insects. Healthy plants tend to be fairly resistant to sap sucking insects such as aphids.

Therefore, preventing aphids and other sap sucking insects means raising healthy plants. Read my blog on creating healthy soil for more information on that matter, including why we need to choose the right plant for the right spot.

We can also control aphids by taking away their key protectors – ants. Ants harvest the honeydew secreted from the aphids (and other sap sucking insects). In return, the ants protect the aphids from some predators. We can bank tree trunks or affected branches with a horticultural glue. This stops ants from reaching the aphids.


Controlling aphids in other violent ways

We can easy crush aphids between our fingers. However, many aphid predators are small and may also be harmed if we don’t take care. Also, when we take aphids away, we are taking away food for our predatory insects. So if we want lady beetles, and hover flies (also excellent pollinators), lacewings and others then we need to provide them with their food sources.

Aphid insects are easily dispersed by a strong jet of water from the hose. However, again we need to ensure there are no predatory insects hunting and consuming the aphids.

If we use chemicals to kill aphids we are contributing to the problem of global insecticide resistance.  I’m astounded that so many government websites still advocate for using systemic killing chemicals for insects such as aphids. It’s overkill and ridiculous.


Aphid insects are a part of nature

We need to start trusting nature and working with nature rather than reaching for a bottle of poison. If we want to raise plants, we need to understand plant ecology and this includes insects, soil, microbes and the plants themselves.
I’ve started the Garden Tara blog for exactly that purpose. Most of the time we don’t need to take any action in our garden. Often, we just need to observe and become aware of our garden and it’s wider ecology.

1 Comment

Roy · June 30, 2020 at 2:20 pm

Last year I grew garlic around my roses. No aphids. easy eh!

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