Aphidius colemani

Small aphids clustered on the new growth — green peach and melon aphid above all. Aphidius colemani is a parasitic wasp about the size of a fungus gnat, with an unreasonable talent for finding a single aphid in a full canopy. It has no sting, no interest in you or your kitchen, and it searches efficiently at low density — exactly where sprays and predators both do worst.

It is also the least work of anything we sell. Nothing to mix, nothing to spray, no residue and no re-entry interval — you open the vial near the plants and the wasps do the finding themselves. They reach aphids tucked into growing tips and leaf undersides a spray would never wet, they keep working at densities too low for you to even see, and aphids cannot develop resistance to being parasitised. Safe around people, pets and anything you plan to eat.

What you will see is not dead aphids. The female lays one egg inside an aphid; a week or so later that aphid becomes a hard, swollen tan shell glued to the leaf — a mummy — with a neat round hole where the new wasp chewed its way out. Count mummies, not activity.

Best for: Small, scattered, early aphid colonies — green peach or melon aphid.
How many: Sizes go by plant count. Under heavy pressure take one size up, and plan a second release 7–14 days later.
Arrives as: Mummies, or already-hatched adults. Small gold-tan shells mean the wasps are either still inside or already out hunting.
Speed: Mummies at 7–12 days; the next generation of adults 4–6 days after that.
Safe around: People, pets, plants and food crops.
Not for: Potato aphid or foxglove aphid, the big pale-green and pink ones — colemani will sting them but cannot develop inside them, so Aphidius ervi is the one there. No thrips, whitefly, mites, mealybug, scale or fungus gnats.