Natural Pest Control: Using Predators to Protect Your Garden

Clive Rolison
Thursday, 26th November 2015

Clive Rolison explains how to attract beneficial predators into the permaculture garden to naturally establish pest / predator balance - even with slugs!

We all know that monocultures provide pests with an abundance of everything that they need to grow from a minor nuisance into a major disaster. For this reason, the use of chemical pesticides has become widespread to the point that it is seen as a necessity for some. Of course, it isn't. 

In a balanced ecosystem pest numbers are kept down by their natural predators. As a healthy permaculture resembles a balanced and resilient ecosystem, we can attract beneficial ‘pest predators’ into our gardens and allotments to protect our crops.

The enemy of my enemy is my friend...

If your crops are being plagued by a particular pest, it might be worth reading up on your pest’s natural predators and seeing what can be done to attract them. One of the many problems with chemical pesticides is that they often not only kill the pest but also the pest’s predator. Slug pellets, for example, will kill hedgehogs as well as the slugs. However, as slugs have a shorter lifecycle than hedgehogs, they will be back in your allotment much sooner than the hedgehogs - and this time around they’ll thrive because you have removed one of their natural enemies. By helping hedgehogs instead of harming them, we create a sustainable long-term to our slug problem.

Hedgehogs are known as a ‘gardener’s friend’ because they eat slugs, snails and other insects that otherwise might eat your crops. Their population is plummeting in Briatin. To encourage hedgehogs, you can use a simple wooden box as a hedgehog shelter, so long as it has a clear entrance that is 13cm tall, and provided that the wood has not been creosoted or otherwise treated. Place the shelter at the wildest edge of your permaculture garden, and cover lightly with soil and twigs. Straw or dry leaves inside the box can act as bedding.

Bats are another useful predator that eat moths, including the notorious leek and codling moths. Bats tend to frequent gardens with water features, hedges and night-scented flowers. You can buy or build a bat-box, though most bats are seasonal visitors to the UK and are unlikely to stay on permanently. Bat-boxes should be placed as high as possible in a sheltered, but sunny spot.

Frogs, toads and newts all eat insects that would like to feast on your garden, particularly slugs. A simple pond that is 2m wide and 60cm deep is ideal for amphibians, though make sure that the sides are gradual. Installing a water feature might not always be practical, but since toads actually spend the majority of their life out of the water, sometimes all you need is a small rock or stick pile to attract one - especially in damp or humid places. You’ll want to be careful if you use netting in your garden, as this can easily trap and kill amphibians.

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Distinguishing beneficial insects from the ‘bad’ ones

While many insects can be problematic for gardeners, there are also a number of beneficial insects that you can attract to your garden with ‘welcome mat’ plants - also known as insectary plants. Ladybirds, hoverflies and lacewings all have larvae which feed on pests, including aphids, giving rise to their appealing nicknames such as ‘aphid lion’ and ‘aphid alligator.’ Ladybirds and lacewings also feed on red spider mites. Angelica, dill, fennel and parsley are all good welcome mats for these ‘beneficials’.

If you are considering using beneficials, remember that they will need access to nectar and pollen all year round, so having welcome mat plants that flower at different times of the year will be necessary. Some garden centres sell ‘good bug’ seed mix. Also remember that you’ll have to tolerate minor pest infestations if you want to make use of beneficial bugs. If you eradicate pests too quickly, then your beneficials will have nothing to eat and will either starve or leave.

Wasps also eat caterpillars and so can be considered beneficial, but some people, understandably, are hesitant to welcome wasps into their garden. Parasitic mini-wasps like the trichogramma wasp, however, do not sting humans yet still act as pest control. They do this by laying their own eggs inside moth eggs, which prevents the moth eggs from hatching into caterpillars that would demolish your garden. If you see a caterpillar covered in white capsules, leave it alone. The capsules are cocoons that will hatch into braconid wasps that will kill the caterpillar in the process.

Braconid wasps and tachinid flies also kill flea beetles. Trichogrammatidae wasps are one of the thrips few natural predators, though some species of thrips feed on mites and can be considered beneficial themselves. Plants like the fern-leaf yarrow, common yarrow and coriander will attract mini parasitic wasps. These are most effective as welcome mats when planted between crops.

For beneficials to be most effective you’ll have to learn to recognise what these insects look like as adults, larvae and even eggs. This is especially important because beneficials often eat more pests as larvae than they do as adults, with the added benefit that they can’t yet fly off and leave you high and dry. So don’t destroy any and all insect eggs you find on your plants, as some of these may actually be allies-in-training.

Should you use nematodes in your garden?

Nematodes, or roundworms can be bought in garden centres as a method of pest control. Beneficial nematodes do occur naturally in the soil too. They eat a variety of common pests including carrot root fly and a variety of soil-based insects. Predatory nematodes are harmless to humans and the vast majority of non soil-based insects, though they will eat butterfly eggs. The main drawbacks to nematodes are the price and the fact that they work best in certain conditions.

Beneficial birds

Birds are champion pest controllers that are also welcome in the garden for their aesthetic value. They eat a wide array of pests, including, snails, caterpillars and cabbage white butterflies. It’s common knowledge that a bird feeder will attract birds to your garden, but it's less well known that the position of your bird feeder will have a significant impact on the number of birds that it attracts. Though different positions work best for different species, in general you want your feeder to be close to cover, high up and as far from people as possible. House sparrows buck the trend by preferring feeders that are close to homes.

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Despite what garden centres will have you believe, a cheap wheat mix is the preferred food for the widest range of birds, though a few oily seeds, such as sunflower, won’t go amiss if you plan to attract finches. Providing your birds with a source of calcium will result in larger broods of fledglings and female birds in better health. Chicken egg shells work well for this purpose, as do snail shells.

Beneficial predators are a natural way to protect your plants that work exceptionally well in a permaculture setting. Though attracting predators can sometimes be a challenge, they have the potential to reduce your workload enormously in the long run.

About the author: Clive Rolison is an expert on sustainability, with a particular focus on renewable energy. He installs solar panels to help people cut their energy bills and reachself-sufficiency.

Further Infomation

20 ways to control slugs in your garden

Crop protection

Bird, Bee & Bug Houses

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