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Encouraging 'Good' Bugs

By: Dr Gareth Evans - Updated: 23 Sep 2012 | comments*Discuss
Beneficial Insects Ladybirds Hover Flies

Not all types of insects are pests – which is just as well since there are nearly a million different sorts around the world. Many kinds are positively beneficial, but who makes up this free and willing workforce ever-ready to help out in the garden and how should we go about encouraging these good bugs?

Natural Pest Controllers

Pests have their natural enemies, which, with a little effort, can be recruited to provide a free and ever-vigilant control service. For example, one well known “good” guy, the ladybird, consumes vast numbers of aphids both when adult and as larvae; lacewing grubs have a voracious appetite for aphids, insect eggs and a number of small caterpillars.

However, some of the good bugs are less well-known. Hover-fly larvae can consume 50 or more aphids in a day, while a large variety of common pests, including aphids, leaf beetles, weevils, wireworms, chafer grubs, caterpillars, fruit flies, leatherjackets, gall midges, flies and slugs form the diet of ground beetles and rove beetles.

Even insects such as wasps and hornets which we might often consider as pests themselves – principally because they tend to make a nuisance of themselves on picnics and sometimes sting us – can also be surprisingly helpful. Contrary to the commonly held belief that these insects have no redeeming features at all, wasps perform a useful service eating aphids and caterpillars and helping clear up the remains of small animals, while hornets consume huge numbers of flies and caterpillars. That other common stinging insect, the bee, is of course, well-known as a gardener’s friend, playing an important role in the pollination and the propagation of many types of flowers, though it does not have a part to play in warding off pests.

Encouraging them in

There are three simple steps to encouraging good bugs – provide food, give them shelter and avoid general pesticide use.

Part of providing food as encouragement means that you will have to tolerate a small population of pests – otherwise there is nothing for your new found allies to eat! Although on the face of it, this might seem to be working against yourself, natural control is about managing the pest numbers and restricting the damage they can do unopposed, rather than eradicating them altogether. Fortunately, this does not always mean that you have to watch your prized blooms under attack; nettle aphids only bother nettles, but they will still attract ladybirds and lacewings to the garden.

Many of the most beneficial insects do most of their pest control as larvae, so it is also important to provide food for the adults, especially during their breeding season, when they are producing the next wave of reinforcements for you. Growing plants which are rich in pollen and nectar will attract them to your garden to mate and lay, giving the essential high sugar foods essential for them to breed successfully. Plants such as members of the daisy family and a variety of herbs including sage, thyme, dill, fennel and mint are ideal.

Even beneficial insects have their predators, so providing them with somewhere to hide or where they can spend the colder months is a good idea. Although it is now possible to buy a range of purpose built “houses” to encourage lacewings, ladybirds and other beneficial species, providing shelter need be nothing more than a few old logs, some slates at the back of the border or even leaving a quiet corner to go a bit wild.

It may also help them to catch up with the pest too – large predatory beetles such as devil’s coach-horses, for example, hide under logs during the day and will happily eat any slugs they find trying to hide there too!

Most of the insecticides sold to deal with insect pests are fairly indiscriminate and can end up killing friend as well as foe – so they are best avoided if you are trying to encourage beneficial species. If it is essential to use pesticides to control a particular pest problem, try to select one of the “systemic” types if an appropriate one is available. These are absorbed into the plant itself and only kill insects that are actually feeding on it. If there is no option other than using a more general product, then it is best to try to apply them in a very specific area only, rather than attempting an all-out chemical assault on the whole garden.

Having beneficial insects in the garden is certainly no guarantee that you never see another aphid on your roses, but then natural control is all about balance rather than out-and-out annihilation. While this may mean that you have to put up with the odd chewed leaf from time to time, in the long run encouraging a resident population of good bugs will give you the best free pest control services there is!

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