Orchids insects on the plant
There are 6 common causes, and they need completely different responses — so working out which one you have matters more than treating quickly.
1 of them can kill the plant. Rule those out first.
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.
The 6 causes, and how to tell them apart
1.Spider Mites
Act nowPest
Fine pale stippling across the leaf, as though it had been sprayed with a very fine dust of pinpricks. Leaves go bronze or grey, and fine webbing appears between leaves and along stems in bad infestations. The mites themselves are just visible as moving specks.
How to know it is this one
Fine even stippling rather than discrete spots or holes.
2.Aphids
TreatablePest
Clusters of small soft-bodied insects, usually green but also black, grey, pink or white, packed along new shoots and the undersides of young leaves. Leaves curl and pucker, and everything below becomes sticky with honeydew.
How to know it is this one
Dense clusters on new shoots and flower buds rather than scattered individuals.
3.Mealybugs
TreatablePest
Small oval insects covered in white cottony wax, hiding in leaf axils, under leaves and in the crevices where stems meet. Heavy infestations look like scattered specks of cotton wool. Sticky honeydew follows.
How to know it is this one
White cottony specks in leaf axils and crevices.
4.Scale Insects
TreatablePest
Small immobile bumps along stems and leaf veins, brown, tan or white, looking far more like part of the plant than like an insect. Scrape one off with a fingernail and there is a soft body underneath. Sticky honeydew and black sooty mould usually accompany them.
How to know it is this one
Immobile bumps that scrape off with a fingernail, leaving a soft body.
5.Thrips
TreatablePest
Silvery or bronze streaking on leaves and petals, speckled with minute black dots of excrement. Flowers open distorted or streaked. The insects themselves are slender slivers under a millimetre long that dart when disturbed.
How to know it is this one
Silvery or bronze streaks, not spots or holes.
6.Fungus Gnats
Mostly cosmeticPest
Small dark flies, a little smaller than a fruit fly, that run across the soil surface and fly in short erratic hops when the pot is disturbed. Larvae are translucent with black heads and live in the top inch of damp compost.
How to know it is this one
Adults run on the soil surface rather than flying around fruit like fruit flies.
Still not sure?
The diagnostic key adds two more questions — which part is affected and where the trouble started — and those usually settle it.
Run the diagnostic key