Your garden, big or small, is an ecosystem where living things interact with each other and their environment. An ecosystem is healthy when the relationships – insect/ insect, plant/insect or living/non-living – within it function well. Formed over many thousands of years, these relationships provide services such as pollination, water filtration and biocontrol.
Biocontrol is the process of using living organisms to manage plant and animal pests with minimal negative consequences. Because spraying, whether organic or not, can lead to unhealthy soil and decreasing pollinator numbers. One of the best forms of biocontrol is to have predatory insects feed on unhelpful pests. To attract them, plant diversity is key; the more beneficial insect attracting plant species you have in your garden, the more beneficial insects you’ll have.
It’s okay to have a few pests in your garden – they will feed the beneficial bugs and help prevent an outbreak. Biocontrol is a terrific permaculture concept, making less work for you and more food to share.
1. LADY BEETLES
Lady beetles have a voracious appetite for pests. Juvenile ladybirds will happily feast on up to 200 aphid or scale insects in a day. Not all lady beetles feed on the same pests, however, so it is best to have a number of species in your garden. Some species feed on foliage so it is important to identify which species are in your backyard. Adults mostly feed upon nectar, so because lady beetles use smell to identify plants, it is worth investing in white-flowered species, which generally have a stronger scent to insects. Letting plants such as dill and parsley go to flower should ensure adults have sufficient food. Indigenous white-flowered options include Brachyscome diversifolia and Rhodanthe anthemoides.
There are 10,000 native wasp species in Australia, many of which perform important services for humans and one group is the Braconid wasp, which range in size from 2–20 mm. Similar in appearance to small flies, a Braconid wasp can be identified by the waving of its relatively long antennae in a fast and continuous fashion. Wasps have poor eyesight and rely on their antennae for sensory cues.
Braconid species inject their larvae into hosts which then feast on the insides after they hatch. This protein allows them to grow and eventually pupate into adults. Some prefer cabbage white butterfly caterpillars, while others prefer scale or aphid hosts. Due to their large size range, it is best to have a range of different white-flowered plants dotted throughout your garden. Alyssum and buckwheat provide excellent small flowers, while indigenous daisies provide a larger landing pad for bigger wasps.
Lacewing adults are magicallooking creatures with long antennae and wings which are larger than their body. The green lacewing is particularly beautiful as it has transparent wings resembling a stained-glass window, as well as large metallic eyes.
The green and brown lacewings, both of which are native to Australia, are commonly found in gardens from October through to mid-summer. The larval stage feeds on up to 200 aphids per day, but they will also eat mites, white fly and scale. A fascinating fact about lacewing larvae is their prey does not see them coming because they camouflage their bodies with the remains of their victims.
Spiders eat almost any insect or spider – beneficial or otherwise – they can comfortably catch. Beneficial insect populations also need to be kept in check, because if a species population count gets too large, they can outcompete other useful insects. Equally, if populations exceed the garden’s capacity, their numbers can suddenly drop. Diversity is the key.
Ideally, your garden has spiders that use webs to catch their prey and also spiders that use ambush tactics. Webs tend to catch flying insects, such as cabbage butterflies, while ambush predators such as wolf spiders or peacock spiders catch insects hanging out in leaf litter or low-lying vegetation. It might seem counter-intuitive to have animals that catch beneficial insects, but balancing numbers ensures greater diversity.
One of the most valuable flies to humans is the hoverfly. As the name suggests, they love to hover and they appear to compute a lot of information in mid-air before deciding on the next flower to visit. Masquerading as bees with stripy patterns on their body to warn off predators, it can be tricky at first to pick up on their presence. In the larval stage they eat aphids, thrips and other sucking insects, but are not as prominent as lady beetle or lacewing larvae. As adults, however, they are excellent pollinators. In fact, some research suggest they may be the most numerous pollinators in some garden or forest ecosystems.