Attract the insects that eat pests by sowing small, open, nectar-rich flowers such as sweet alyssum, dill, fennel, coriander and yarrow in and around the crop so that something is in bloom all season, by leaving undisturbed mulch, stone and grass for shelter, and by avoiding broad-spectrum sprays. Many predators and parasites are predators only as larvae, and the adults need nectar and pollen to lay eggs.
Beneficial insect attractors are plants and habitat that supply nectar, pollen and shelter to the natural enemies of crop pests.
Adults Need Flowers, Larvae Eat Pests
The pattern repeats across the groups the carrier lists:
- Hoverflies: the larvae eat aphids; the adults feed on nectar and pollen.
- Lacewings: larvae are voracious aphid predators; the adults of the common species feed on nectar, pollen and honeydew, so flowers keep them near.
- Parasitic wasps (tiny, non-stinging): the female lays eggs in caterpillars or aphids; the adults need nectar from small flowers because their mouthparts are short.
- Ladybirds: both adults and larvae eat aphids; flowers and aphids themselves keep them in the crop.
- Ground beetles: nocturnal predators of slugs, cutworms and root maggots; they need undisturbed ground cover, not flowers.
Spiders eat everything and need undisturbed habitat.
Plants To Sow
Short-mouthed insects reach nectar only in shallow flowers. The carrier names yarrow, dill, fennel, coriander and small-flowered plants such as alyssum and parsley in bloom. Pest-Confusing Polycultures adds chamomile and notes that flower support for natural enemies is better supported than repellent herbs.
| Need | Provide |
|---|---|
| Spring nectar | Early flowers such as borage or bolting brassicas left in a corner |
| Summer nectar | Alyssum, dill, coriander, fennel, yarrow, buckwheat |
| Late-season nectar | Late-flowering herbs and asters |
| Shelter | Undisturbed mulch, stone borders, tussock grass, a woodpile |
| Water | A shallow dish with pebbles |
Method
- Place flowers within reach of the crop. Natural enemies stay near their food; put a strip of flowers every few beds or along the edge, not just in a far corner.
- Keep something in bloom through the season. A gap of a few weeks with no flowers drives parasites away.
- Leave some ground undisturbed for beetles and spiders: do not rake every border bare.
- Do not spray broadly. Even plant-based sprays kill beneficials (Integrated Pest Management (IPM)).
- Judge by the crop. Count aphid colonies with and without nearby flowers and keep what works (Pest-Repelling Plant Combinations).
Several Of The Best Flowers Have Deadly Lookalikes
Many flowers that suit beneficial insects belong to the carrot family (dill, fennel, coriander, parsley, carrot, wild carrot) and have flat umbrella heads. Let carrots go to seed only if you can tell them from wild relatives, and remember that wild carrot crosses with the garden carrot.
Poison hemlock and water hemlock look like carrot-family flowers
Poison hemlock and water hemlock have similar umbrella flower heads and are deadly if eaten; a single bite of water hemlock can kill an adult (Poisonous Plants). Never collect umbels from the wild to “attract insects”, never plant a stand you cannot name, and teach children to treat any unknown umbel as poison.
Costs
- Land: a strip of flowers displaces some crop.
- Competition: tall flowers shade lettuce and shelter slugs.
- Time: the flowers must be sown, weeded and cut back.
Common Mistakes
- Planting flowers far from the crop. The enemies stay by the flowers.
- A single bloom period. Parasites leave when the nectar ends.
- Cutting every border bare. It removes the beetles’ shelter.
- Importing predators without habitat. Released ladybirds disperse within days if there is nothing for them.
What’s Next
- Learn next: Biological Controls — the wider strategy
- Combine with: Predator Encouragement — the larger animals