Field Notes · Plant Health
Pests & problems
Identify what's eating your plant — start from the symptom, match the culprit, treat with the gentlest thing that works. Includes the look-alikes that aren't bugs at all.
Start from the symptom
You usually notice damage before you notice the animal. Read down the left column, then jump to the matching profile below. Check leaf undersides and new growth first — that's where most of these live.
Spider mites. Tiny moving dots under the leaf; webbing across tips when advanced. Loves hot, dry, still air.
Aphids, mealybugs, scale, or whiteflies — all sap-suckers that excrete sticky honeydew, which grows sooty mold. Find which one by looking for the animal.
Mealybugs. In leaf axils and under bracts; if the plant declines with a clean top, tip it out and check for root mealybugs (white crust on roots and pot walls).
Scale. Waxy limpet-like shells that don't move and pick off with a fingernail, leaving a mark.
Thrips. Slender, fast, splinter-sized; the black specks are frass. New leaves emerge scarred and twisted.
Fungus gnats. Adults are harmless but larvae chew fine roots and seedlings in wet media.
Whiteflies. Clouds of tiny white wedges underneath leaves; sticky honeydew below.
Slugs & snails. Outdoor and greenhouse plants; hunt them at night with a torch, check under pot rims.
Pest profiles
The eight you'll actually meet. "Pressure point" is where an infestation usually starts — check it during watering and you'll catch problems a month early.
- Spider mites
- ID: pinprick stippling, bronzed leaves, webbing at leaf tips; mites are dust-speck sized, often reddish. Pressure point: hot dry spells, plants near heaters/vents. First move: shower the whole plant, raise humidity, repeat weekly — they hate wet.
- Aphids
- ID: soft pear-shaped clusters on new growth and flower stalks; green, black, or pink; sticky honeydew below. Pressure point: fresh flushes of growth, spring. First move: blast off with water or wipe; repeat every few days — they rebound fast.
- Mealybugs
- ID: white cottony ovals in leaf axils, under leaves, on stems; slow-moving. Pressure point: succulents, hoyas, orchids; anywhere tight and hidden. First move: dab each one with a cotton bud dipped in 70% isopropyl alcohol.
- Root mealybugs
- ID: plant sulks with no visible pest; white powdery deposits on roots and inner pot wall at repot. Pressure point: dry-grown succulents and cacti. First move: bare-root, rinse everything, discard the old mix, pot fresh.
- Scale
- ID: tan-to-brown waxy bumps that don't move, along stems and leaf midribs; sticky film below. Pressure point: ficus, citrus, orchids. First move: scrape off with a nail or alcohol swab; follow up — crawlers are invisible.
- Thrips
- ID: silvery patches with black dot frass; splinter-like insects that scatter when disturbed; deformed new leaves. Pressure point: aroids and flowering plants. First move: blue/yellow sticky traps + remove worst leaves; be persistent, the pupae hide in the mix.
- Fungus gnats
- ID: wobbly black flies over the soil surface; larvae are glassy threads with black heads in the top few cm of mix. Pressure point: peat-heavy mixes kept constantly wet — including carnivorous plant trays. First move: let the top of the mix dry where the plant allows it, yellow sticky traps; BTI (mosquito bits) in the watering can clears larvae safely.
- Slugs & snails
- ID: ragged-edged holes, silvery dried slime trails; damage appears overnight. Pressure point: outdoor Sarracenia bogs, shade houses. First move: night patrol with a torch; copper tape around benches; keep the area free of hiding boards and debris.
Looks like a bug — isn't
Half of "what's this pest?" posts are cultural problems. Rule these out before you spray anything.
- Oedema
- Cork-like blisters or bumps under leaves after overwatering in low light — cells burst from pressure. Not contagious; fix the watering rhythm.
- Sunburn
- Bleached-then-brown papery patches on the sun-facing side only, appearing within a day of moving the plant. Nothing to treat — shade it and let new growth replace the damage.
- Fungal leaf spot
- Round spots with darker rings that slowly expand — no insects present. Improve airflow, keep foliage drier, cut off the worst leaves.
- Root rot
- Wilting despite wet soil, sour smell, brown mushy roots. It's the watering, not a pest. Unpot, trim to firm tissue, repot in fresh airier mix.
- Mineral burn
- Crispy leaf edges and white crust on the pot — hard tap water or fertilizer salt. Carnivorous plants are the extreme case: they need rain/RO/distilled water, and fertilized soil can kill them.
- Nectar & guttation
- Sticky droplets on Nepenthes peristomes and tendrils, or dew-drops at leaf tips in the morning, are normal plant secretions — not honeydew. If there's no insect and no sooty mold, it's fine.
The treatment ladder
Always start at the bottom rung and only climb if the pest persists. Log every treatment as a Sprayed care action so your timeline shows what worked.
Move the plant away from the collection the moment you spot anything. Most outbreaks are one missed quarantine.
Shower the plant, wipe leaves, alcohol-swab mealies and scale, hand-pick slugs, hang sticky traps. Repeat weekly — you're breaking the life cycle, not winning in one pass.
Insecticidal soap or horticultural/neem oil, covering leaf undersides, out of direct sun. Test one leaf first — dewy sundews, waxy succulent bloom, and some ferns react badly.
Predatory mites for spider mites/thrips, BTI drench for fungus gnat larvae. Slow but thorough, and safe around carnivorous plants.
For entrenched scale/mealy/thrips only. Follow the label exactly, never on plants visited by pollinators, and know that carnivores digesting treated insects is an open risk — many growers keep systemics away from them entirely.
Prevention beats identification
The boring habits that make this whole page academic.
- Quarantine new plants
- Two to four weeks apart from the collection — long enough for hitchhiker eggs to hatch and show themselves.
- Inspect while you water
- Flip a few leaves every session. Your growth-log photos double as a pest history — zoom into last month's shot to date an infestation.
- Airflow & spacing
- A small fan and a little space between pots makes life hard for mites, fungus, and scale crawlers alike.
- Water right
- Most "pest" deaths are root problems. Let the mix breathe where the species allows, and give carnivores the pure water they demand.