Beneficial insect
Syrphid fly
Looks like a tiny wasp, stings nothing, and its larva quietly eats your aphids.
How to spot it (and its larva)
Adults are bee- or wasp-mimics: small flies, often with yellow-and-black banded abdomens, that hover dead-still in mid-air over flowers and dart sideways. They have two wings (not four) and no sting. The disguise is pure bluff. They're among the garden's best pollinators as a bonus.
The larva is an inconspicuous, legless, greenish or brownish maggot that slides over leaves like a tiny slug, grabbing aphids and rasping them dry. Most gardeners never notice it working.
How to invite it in
You don't buy most beneficials. You build the habitat that keeps a wild population breeding on-site. Do these and they come, and stay.
- Plant a band of shallow, open flowers
Adults have short mouthparts and need easy nectar: sweet alyssum, calendula, buckwheat, dill, and yarrow are magnets. Alyssum edging a bed is a classic hoverfly lure.
- Sow a flowering cover strip
A strip of buckwheat or phacelia near the veg beds feeds hoverflies (and bees) all season and gives their larvae a base near your aphid-prone crops.
Plants and habitat that bring them in
Small-flowered plants feed the adults so they stay and breed. A packet of these does more for lasting control than a bag of mail-order bugs.
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Don't undo it
The fastest way to lose a beneficial is a broad-spectrum spray. It kills the predators faster than the pests and triggers a worse rebound.
- Insecticides that hit the adults on the flowers they're pollinating
- Swatting them as 'wasps', which cannot sting and they're on your side
- Mowing or clearing every flower, which starves the nectar-dependent adults
Questions about syrphid flys
Is the hovering wasp-striped thing over my flowers going to sting me?+
No. That's a hoverfly (syrphid fly), a stingless fly that mimics a wasp for protection. It pollinates your flowers and its larvae eat aphids. Welcome it.
Plan a garden good bugs want to live in
PlotToTable sizes your beds, spaces every crop for airflow, and flags the pests that hit what you grow, so the predators that eat them have a reason to stay.