Potato insects on the plant
There are 4 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 4 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.Flea Beetles
TreatablePest
Dozens of tiny round holes through the leaf, as though it had been hit with birdshot. The beetles are minute, dark and shiny, and jump like fleas when disturbed — which is usually all you see of them.
How to know it is this one
Many small round shot-holes rather than a few large ones.
4.Tomato Hornworm
TreatablePest
A green caterpillar up to four inches long with white diagonal stripes and a curved horn on its rear end. Entire branches are stripped bare overnight, and dark green pellets of frass collect on the leaves below.
How to know it is this one
Whole stems stripped to bare stalks, not scattered holes.
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