How to encourage beneficial bugs that help your garden grow

As gardeners, we have learned so much in recent years about how we can help support the country’s butterfly and bee populations. But what about the other common garden insects and invertebrates that play such an important role in the delicate, complex ecosystems of our gardens and allotments, from boosting pollination to protecting soil health and helping to control pests. Here’s a look at some of them . . .

Hoverflies

Hoverflies are often seen hovering over plants (hence their name) from late spring to early autumn. Ireland is home to 180 native species of these dainty, non-stinging, pollinating insects, many with black-and-yellow markings that make them resemble miniature wasps at first glance. Adult hoverflies feed on the nectar and pollen of flowers, assisting pollination by transferring pollen from flower to flower. The larvae of some species also feed on common garden pests such as greenfly, psyllids (plant suckers) and caterpillars while others help to keep your garden healthy by eating dead and decaying plant matter.

How to encourage them? Many species of hoverfly are aquatic or sub-aquatic with larvae that need wet, muddy places while others need decaying plant matter. Suitable garden habitats include garden ponds, bog gardens and compost heaps. Adult hoverflies are also particularly attracted to umbelliferous flowers (open blooms with an undercarriage that resembles an umbrella) such as those of ammi, fennel, dill, parsley, ground elder and ornamental carrot. They also like to feed on the flowers of wild buttercup, ivy, privet, elder, euonymus, hazel, sycamore and lime.

Ladybirds

Few insects are as instantly identifiable as the native seven-spot ladybird with its smart red and black-spotted wings. In spring it cleverly lays its pale-yellow eggs close to aphid colonies where its carnivorous larvae love to guzzle on greenfly and blackfly. Ladybirds also help to control other common sap-sucking garden pests such as whitefly, thrips, plant lice and scale insects by feeding on them and are useful pollinating insects, resulting in larger crops of fruit, vegetables and seed.

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How to encourage them? Avoid using chemical insecticides and provide suitable habitats for these pretty, beneficial insects to feed and overwinter. Along with eating sap-sucking pests, adult ladybirds feed on flower nectar, especially from umbelliferous varieties such as those mentioned above. Suitably sheltered, undisturbed spots in which the adult ladybird likes to overwinter include piles of old leaves, hollow plant stems, garden sheds, “bug homes” and small fissures/gaps in walls, window frames, fencing as well as on coniferous trees (which is why they’re often accidentally brought into the house on Christmas trees). They’ll then emerge in April to mate, after which the female lays its eggs.

Earthworms

Typically inhabiting the upper 15cm layer of soil, although they can burrow much deeper, earthworms can be found everywhere in a healthy garden from vegetable beds, flower borders, lawns and compost heaps to meadows, woodlands and shrubberies. The invaluable multitaskers of our gardens and allotments, they play a crucial role in aerating the soil, improving its structure, drainage and fertility, and generally supporting soil health. As “detrivores” or decomposers that feed on dead plant material which they then reincorporate back into the soil as humus, they’re also one of nature’s great recyclers. Earthworms are also an important food source for many kinds of garden birds and other garden wildlife including frogs, shrews, hedgehogs, foxes and badgers.

How to encourage them? Avoid overcultivating/overworking the soil and using chemical pesticides (especially neonicotinoids) and synthetic fertilisers, all of which have a detrimental effect on earthworm populations. Also bear in mind that when used over an extended period of time, even organically-acceptable garden chemicals such as ferrous phosphate-based slug pellets are bad for earthworm populations.

Lacewings

Another group of delicately beautiful, beneficial insects, lacewings earn their common name by virtue of the prominent veins on their wings. They are mainly nocturnal and the adults often feed on pollen and honeydew (the sugary substance excreted by aphids) while their larvae feed voraciously on the aphids, acting as an excellent form of natural biological pest control.

How to encourage them? Avoid the use of pesticides and insecticides, grow a wide range of umbelliferous flowering plants and try not to be too tidy-minded as both the pupae and the adults of some species like to overwinter in dry, sheltered, undisturbed spots including garden sheds and houses.

Ground beetles

Ground beetles play a vital role in our gardens and allotments, some feeding on slugs, snails, springtails, aphids and vine weevil larvae, others on animal waste or decaying animal remains while others help to break down rotting plant material. Many also feed on the nectar and pollen of flowers, making them excellent pollinators while they’re also an important food source for insect-eating garden wildlife including birds and garden mammals.

How to encourage them? Lawns, compost heaps, woodpiles, undisturbed piles of leaf litter, rockeries and stumperies are all examples of beetle-friendly habitats that will provide shelter for different species. Growing a wide variety of spring-, summer- and autumn-flowering plants will also provide food for species such as the pollinating soldier beetle, which feeds on slugs and aphids but also eats pollen and nectar, and the swollen thigh beetle, which feeds on the nectar and pollen of bright, colourful flowers (“single” or open-structured types rather than “double” kinds with lots of petals). Many species also feed on common weeds so try to leave some wild patches where these can grow. Ground beetles are highly sensitive to pesticides, another reason to steer clear of these environmentally-harmful garden chemicals.

Parasitic wasps

Parasitic wasps are another beneficial, non-stinging group of small insects that play a vital role in our gardens and allotments by helping to maintain a healthy, balanced and biodiverse ecosystem. They lay their eggs on or inside the body of their targeted host insect. As the larvae hatch, (this bit’s a little gruesome) they then feed on the host insect and kill it. Many species feed on aphids, others on mealybugs, caterpillars and leaf miners, which is why they’re often used as a form of natural pest control in commercial horticulture.

How to encourage them? Avoid the use of pesticides and insecticides and instead allow nature to do the work for you.

Spiders

Spiders are natural predators that consume vast quantities of common garden pests and are very important in terms of helping to maintain a healthy, balanced ecosystem in your garden or allotment. Ireland is home to several hundred species, the overwhelming majority of which are harmless to humans (the exception is the non-native Noble false widow spider which can give a nasty bite if suddenly disturbed). Spiders are also an important part of the food chain as prey for birds, frogs, toads, mice and other creatures. So are their close relatives, the nocturnal harvestmen, spider-like scavengers and predators that feed on slugs, snails, caterpillars, mites and woodlice.

How to encourage them? Make space for spiders and harvestmen in your garden or allotment by avoiding the use of pesticides, leaving the spider’s webs and silky-white egg bundles undisturbed, and providing them with suitable habitats such as log piles, leaf litter, walls and old seed-heads in which they like to overwinter.

Centipedes and millipedes

Among the oldest species on Earth, centipedes and millipedes are not liked by the squeamish but are important nocturnal garden predators that feast on a variety of garden pests while also hoovering up decaying garden vegetation. They’re also tasty prey for garden birds, hedgehogs, frogs and ground beetles.

How to encourage them? Centipedes and millipedes like a cool, damp and dark place to hang out, for example, beneath rocks, under log piles or in damp leaf litter, where they can hide away from bright sunshine as well as from predators.

For more information on the above, see pollinators.ie, biodiversityireland.ie, buglife.org.uk, wlgf.org

This Week in the Garden

Keep regularly deadheading any faded flowers on bedding displays/annuals to encourage the plants to produce fresh blooms. Many early-flowering perennials can also be encouraged to produce a second, later, smaller flush of flowers if they are cut back hard after flowering and the plants are given a generous watering followed by a liquid feed rich in potash. Suitable species for cutting back this way include geum, delphiniums, lupins and perennial geraniums.

Keep tying in the growing stems of sweet pea and make sure that plants are regularly watered and liquid-fed every 1-2 weeks to encourage the plentiful production of their sweetly-scented flowers. Generous watering also encourages longer flower stems. Sweet pea flowers must also be picked regularly to prevent the plants from putting their energies into producing seed.