What are the small white bugs in my soil?

Q: What are the small white bugs in my soil?

Small white bugs in cannabis soil that jump when disturbed are almost always springtails: about 1.5 mm (1/16 in), harmless scavengers of wet, organic media. Slow, round specks are soil mites, often harmless or predatory. The ones that matter are worm-like larvae with a shiny black head (fungus gnats) and pale aphids clustered on roots (root aphids). Tip the plant out and look at the roots.

Short answer

Tiny white bugs that jump when you water or poke the soil are almost certainly springtails, about 1.5 mm (1/16 in) long and harmless to established plants. Worry instead about black-headed larvae (fungus gnats) or pale aphids on the roots (root aphids). Established.

Why

Springtails are scavengers. They live in moist, compost-rich soil and potting mixes, feed on fungi and decay, and jump using a folded tail. Mature plants are not significantly injured, and sprays are generally not recommended ^[1].

Fungus gnat larvae do chew roots. They are translucent white, up to about 6 mm, with a shiny black head, and they hurt seedlings and clones most ^[2].

Root aphids feed on roots, out of sight. Pale to olive colonies on the rootball cause slow growth, wilting and yellowing that look like a nutrient problem ^[3].

Soil mites are usually neutral or helpful. The predatory soil mite sold for gnat control eats gnat larvae, thrips pupae and springtails ^[4].

The numbers

Bug	Size and look	Behaviour	Harmful?
Springtail	~1.5 mm, white to grey	Jumps when disturbed	No, except very young seedlings
Soil mite	About 0.5–1 mm, round, tan or white	Crawls slowly	Usually no
Fungus gnat larva	Up to ~6 mm, worm-like, black head	In top few cm of wet media	Yes, for seedlings and clones
Root aphid	Small, pale to olive, pear-shaped	Clusters on roots, doesn't jump	Yes

What to do

Watch a few seconds: jumping means springtails.
Lay a raw potato slice on the medium for 2–4 days; larvae underneath mean gnats.
If the plant is stalling, tip it out and inspect the roots with a 10x lens.
Let the top 2–5 cm (1–2 in) dry between waterings and empty saucers.
Treat only what is harmful: Bti or nematodes for gnats; see the root aphid article for those.

Common mistakes

Drenching insecticide for harmless springtails.
Missing root aphids because "it's just springtails".
Keeping the medium soaked, which feeds every bug on this list.

Full article: Fungus gnats: the watering problem with wings
Article: Root aphids
Answers: Do sticky traps work? · White fuzz on soil
Terms: root aphid · Bti · Stratiolaelaps scimitus

Follow-up questions

Are springtails bad for cannabis?

Springtails are not bad for established cannabis. They are tiny, wingless scavengers about 1.5 mm (1/16 in) long that feed on fungi and decaying matter in moist soil, especially compost-rich mixes. Some species may chew very young seedlings, but mature plants are not significantly injured and control is rarely warranted. Large numbers mainly tell you the medium stays very wet.

How do I tell springtails from root aphids?

Tell springtails from root aphids by behaviour and location. Springtails jump when disturbed, using a spring-like tail, and run over the soil surface or saucer water. Root aphids do not jump; they are pale to olive, pear-shaped insects clustered on roots, often near the edge of the rootball, and the plant slowly stalls and yellows. Tip the plant out to check.

How do I get rid of springtails?

Get rid of springtails by drying things out, not by spraying. Let the top of the soil dry slightly between waterings, empty saucers so drainage water does not stand, and avoid piling excess organic mulch on the pot surface. Insecticide sprays are generally not recommended for springtails. If numbers stay high in a dry-surfaced pot, check that you are not dealing with fungus gnats.