The Wildlife Garden – How to attract beneficial insects to your garden
Integrative Pest Management (IPM) is the use of multiple pest preventative measures, such as diverse crop planting, crop rotation, green manures and responsible pesticide use. Enlisting the help of beneficial insects is also used to control pest populations and improve crop production.
Insectaries are plants that provide housing, shelter and food for beneficial insects. They do not only attract insects to the garden, but provide an area for them to establish themselves and remain in the garden. Insectaries are great for attracting a myriad of wildlife to the garden, such as bees, butterflies, various other pollinators (wasps, flies and beetles) as well as predatory insects such as hover flies, ladybirds, praying mantids and spiders.
I have tried many of the artificial insect home designs, most remain unoccupied, even after being in the garden for two years. The only one that has been populated is House Wasp, details comming soon! I have noticed that the insects prefer plants to purpose built insect homes and I have decided to rather make an insectary in my garden.
Several scientific studies have recorded the successes of these insectaries. Insectaries increase the amount of beneficial insects by 10-fold as compared to plots without one (AKA the control plot). Mortality of pest insects due to predation and parasitism was double as compared to the controls. The beneficial insect numbers remain the same, even if no flowers were present, indicating that they do not leave if no pollen or nectar rewards are present. (Ref 1)
One thing to keep in mind is that the insectary should provide food – not only pollen and nectar, but prey items too. This means that you must incorporate plants that attract pests (sink or source plants); also known as sacrificial or decoys among companion planting. If you do not provide food – the predators will leave. This also means no chemical pesticides!
Another tip is to leave the insectary undisturbed, with minimal pruning of the plants. There is a 75-95% reduction of spiders, parasitic wasps, ladybug adults and larvae in clear-cut plots when compared to strip harvest plots (Ref 2).
A successful insectary has the following characteristics:
✓ Plants provide blooms throughout the year
✓ Plants of varying size and height provide shelter for insects in different niches
✓ Is a long term and permanent feature of the garden
✓ Densely planted and interconnected by plants with little disturbance
✓ Provides small flowers for parasitoids (insect parasites), hover flies, wasps and robber flies
✓ Provides large and long flowers for butterflies, bees and flies.
✓ Provides sturdy herbaceous shrubs for mantids to lay their egg casings against
✓ Provides perennial and annual plants
✓ Diverse types of plants (usually 6-7 types)
(Niche: Spatial or dietary condition where specific organisms are found, such as tree-dwelling, ground-dwelling, carnivore or herbivore.)
There are specific plants that attract specific pests. The best way to design your insectary is to known:
- Which pests you struggle with
- Predators of your problem pests
- Plants that attract predators and those can act as decoys for pests
- Cost and maintenance of these plants
|Pest||Predator or Parasitoids|
|Aphids||Parasitoid wasp, Parasitoid midge, Damsel bugs (Nabidae), Dicyphus bugs (Miridae), Hoverflies, Lacewings, Ladybugs (Ladybird or Lady Beetle), Pirate Bugs (Flower bugs, Anthocoridae), Baby mantids|
|Caterpillars||Mantids, Ground beetles, Paper wasps (Vespidae), Mud daubers wasps (Sphecidae), Parasitoid wasp|
|Eggs of pest insects||Damsel bugs (Nabidae), Parasitoid wasp, Hover fly larvae|
|Leafhoppers||Damsel bugs (Nabidae), Mantids, Spiders, Lacewings, Ladybugs (Ladybird or Lady Beetle), Mud daubers wasps (Sphecidae)|
|Mealy Bugs||Mealy bug ladybird, Parasitoid wasp, Lacewings|
|Red spider mites||Predatory mites, Dicyphus bugs (Miridae), Ladybugs (Ladybird or Lady Beetle), Pirate Bugs (Flower bugs, Anthocoridae)|
|Scale bugs||Lacewings, Ladybugs (Ladybird or Lady Beetle), Parasitoid wasp|
|Snails/Slugs||Ground beetles, Predatory snails (Rumina decollate)|
|Whitefly||Dicyphus bugs (Miridae), Parasitoid wasp|
|Damsel bugs (Nabidae)||Foeniculum vulgare (Fennel)|
|Dicyphus bugs (Miridae)||Digitalis (Foxglove), Verbascum thapsus (Great or common mullein).|
|Ground beetles||Amaranthus (Amaranth) or ground covers (creeping thyme, oregano)|
|Hoverflies*||Aurinia saxatilis (Golden Alyssum), Convolvulus minor(Dwarf morning glory), Cosmos bipinnatus (Garden Cosmos), Daucus carota (Queen Anne’s lace, wild carrot)+, Iberis umbellate (Candy Tuft), Limonium latifolium (Statice), Lupinus spp. (Lupin), Petroselinum crispum (Parsley).|
|Ladybugs (Ladybird or Lady Beetle)Mealy bug ladybird*||Achillea filipendulina (Yarrow), Anethum graveolens (Dill), Convolvulus minor (Dwarf morning glory), Daucus carota (Queen Anne’s lace, wild carrot)+, Foeniculum vulgare (Fennel), Tanacetum vulgare (Tansy)|
|Lacewings*||Achillea filipendulina (Yarrow), Angelica gigas (Angelica), Anethum graveolens (Dill), Cosmos bipinnatus (Garden Cosmos), Daucus carota (Queen Anne’s lace, wild carrot)+,Foeniculum vulgare (Fennel), Tanacetum vulgare (Tansy)|
|Mantids||Sturdy herbaceous herbs (Rosemary, Basil, Lavender)|
|Paper wasps||Aggregate fruit flowers (Raspberry, Strawberry, Dewberry and Blackberry)|
|Parasitoid midge||Anethum graveolens (Dill), Lupinus spp. (Lupin)|
|Parasitoid wasp||Achillea filipendulina (Yarrow), Anethum graveolens (Dill), Cosmos bipinnatus (Garden Cosmos), Lupinus spp. (Lupin), Helianthus annuus (Sunflower), Limonium latifolium(Statice), Melissa officinalis (Lemon balm), Petroselinum crispum (Parsley)|
|Pirate Bugs (Flower bugs, Anthocoridae)||Helianthus annuus (Sunflower), Leucanthemum X superbum (Shasta daisy)|
|Predatory mites*||Helianthus annuus (Sunflower), Leucanthemum X superbum (Shasta daisy)|
|Predatory snails (Rumina decollate)*||Burrows in the soil.|
|Spiders||Structural plants – Our Sterlitzea and herbs (basil and rosemary) provide shelter and web support.|
*Can be purchased
The table is a generalised list of plants to attract insects. It is the flower shape and structure and the specific species that attracts beneficial insects. Many small flowers in Umbels (umbrella shaped) attract predatory insects, such as lady bugs, hoverflies, parasitoids. Most of the plants used to attract insects belong to the Parsley family (Apiaceae), for pollen and nectar, or the Aromatic herb family (Lamiaceae), for shelter and housing. Sacrificial plants include rue, nasturtiums, milkweed, marigold and the mustard family. Alliums (Onions, garlic, chives) also produce lovely umbel flowers.
Note on parasitoids: Parasitic wasps and midges are good biological control agents that can be easily purchased for garden release. The problems with them are that they need specific temperatures and humidities. The wind will blow them away and they will fly away without attacking pests when released into the garden, which make them more suited to indoor greenhouse use than for the conventional vegetable garden.
Several plant species are better suited than others to attract pollinators, such as bees and butterflies. Yarrow, Angelica, Butterfly bush (Buddleja davidii), Sunflowers, Lavender (Lavendula angustifolia), Rosemary (Rosmatinus officinalis), Basil (Ocimum basilicum), Alfalfa (Medicago sativa) and Tall Verbena (Verbena bonariensis) are the most effective at attracting butterflies, bees, bumble bees, hoverflies and moths. I am not going to plant butterfly-specific plants as our area has a general deficit in these. Basil and Lavender produce flowers throughout the year, whereas Dill and Fennel can be planted in autumn and winter, and the Sterlitzea and Aloes are late flowering (winter).
So in my garden I have issues with aphids, whitefly, leafhoppers, scale bugs and caterpillars. This means I am going to try a combination of: Lavender, Dill, Buddleja, Mints, Creeping thyme, Mint-Basil, Alfalfa, Parsley and Fennel. I also planted a sea lavender, iceplants (AKA plakkie: Aptenia hybrid ‘Red apple’) and rose mosses (Portulaca grandiflora). I have raspberries in the garden already. I have a range of other ornamentals and herbs in the garden that I do allow to flower for a short time, which should also double as ‘mini and temporary’ insectaries.
The insects discussed here have already or will feature in Pest of the Month or Garden Critter of the Month articles! Otherwise you can check out my Pest Control page for some organic pest control recipes to complement your insectary and IPM.
Which pests plague your garden? Would you make space for an insectary in your garden?
Profile posts on most of the herbs, insects and pests are soon to follow!