Making insects feel at home

Increase your garden’s biodiversity by putting out a welcome mat for the little guys.

Praying mantises are useful in controlling harmful insects

Praying mantises are useful in controlling harmful insects

When an infestation of aphids, mealy bugs or other common garden pest appears in our gardens it is tempting to look for a quick fix such as a chemical spray.

But a better solution is to work towards a balance where nature is doing most of the work for us. Attracting beneficial insects is a major part of creating a balanced ecosystem in our gardens that does not require expensive and sometimes toxic chemicals.

A healthy garden is good for conservation because it can help increase numbers of native insects, lizards and birds.

“The main things to remember are to provide places for insects to live, to have plenty of variety in your garden and to ensure there are always food sources available. It’s important to keep things in balance,” says Kaye Reardon, a Wellington garden consultant, who uses organic principles in her Grow From Here business.

The proof is in her own garden, where a great variety of plants thrive despite being on a ridge top exposed to Wellington’s wild elements.

She points out that even the insects and garden bugs that most vex gardeners – including aphids, slugs and snails – are useful too. Aphids can clean up plants by killing off the diseased and stressed parts, and slugs and snails help break down dead leaves and other material.

“It’s not so much that some insects are harmful but it’s more about their numbers,” says Kaye. If there is an infestation of aphids and whitefly, the plants are probably stressed and the garden is out of balance.

One way of helping to avoid major infestations is by encouraging predator insects into your garden. One of the most important in New Zealand gardens is the hoverfly. As well as pest control, they have other uses too. “Hoverflies are great; they do a great job pollinating as well as controlling other potentially harmful insects,” says Kaye.

“Not everything is bee pollinated, but bees take all the credit.”

Other useful insects include lacewings, praying mantises, ladybirds, ground beetles, earwigs, bees and native wasps and assassin bugs. Spiders, centipedes and some mites are also helpful hunters.

It is important to have plants in flower for as much of the year as possible to attract insects. These include the native and introduced bees that pollinate your garden but also other insects that can act as pollinators and predators of common garden pests.

Most native insects have short tongues, so plants with small open blooms – especially native species – are best for attracting them. Invertebrate ecologist Alison Evans recommends Olearia species, köhühü, lemonwood, ribbonwood, cabbage tree and hebes as some of the best native species to attract insects.

Most of our gardens contain many introduced plant species – particularly in our vegetable plots – that attract introduced insects that can become pests, so it is necessary to attract the introduced insects that prey on them as well.

Excellent plants for attracting large insect numbers include borage, calendula (marigolds), phacelia, lavender and sunflowers.

One of the most important steps you can take is to ensure there are good places for the beneficial insects to live and shelter. You can build elaborate insect hotels but there are simpler ways. Insects like long grasses and hedges, and Kaye has a terracotta garden ornament that is a favourite with wëtä and other insects.

It is also a good idea to provide water, even if it is only the odd small dish.

“In the end, it is about having lots of variety in the garden and lots of things going on. That’s what pleases me about my garden and that will keep the insects happy too,” says Kaye.

Create a garden for insects DIY conservation

  1. Any great garden starts with good soil. To create a garden full of a wide variety of healthy plants, which attract lots of useful insects, add compost and mulch to create quality soil.
  2. The fewer chemical sprays you use the better. Any broad-spectrum insecticide will wipe out the beneficial insects along with the potential pests and make a future infestation more likely.
  3. Plant a wide variety of flowering plants. To attractbeneficial insects to your garden and to keep them there, it is important that there are plants in flower for as much of the year as possible. Many insects, such as hoverflies, rely partly on flower nectar and pollen as part of their food supply. Some gardeners also encourage small populations of pest insects to keep the predators interested.
  4. Many gardens will include both native and introduced plants. Some of the most useful insects are natives. They have short tongues, adapted to the small open flowers of native plants, so it is worth including natives for that reason alone. Olearia species, köhühü, lemonwood, ribbonwood, cabbage tree and hebes are good natives to have in your garden.
  5. Shelter for insects is important. Long grasses and hedges around the fringes of your garden are good. Garden ornaments, pots and other artificial shelters can also make good insect homes.
  6. Read about attracting bugs to your garden in Backyard Bugs: A guide to pest control in the home and garden by Bruce Chapman (Dunmore Publishing, 1998).
  7. Many plants, especially in the vegetable garden, will not be native. They will attract introduced pests, so it is a good idea to include plants that will attract their predators. Planting a variety of herbs and flowering plants around vegetables and fruit trees will attract the predators that keep pests in check. Among the most useful flowering plants are phacelia, which can be replanted monthly to ensure ongoing flowering, borage, calendula, buckwheat, lavender and sunflowers.