Citrus sticky leaves
There are 4 common causes, and they need completely different responses — so working out which one you have matters more than treating quickly.
None of them will normally kill the plant.
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.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.
2.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.
3.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.
4.Sooty Mould
Mostly cosmeticFungal disease
A black, dry, soot-like film coating the upper surfaces of leaves and stems. It wipes off with a damp cloth, leaving green leaf underneath, and it is always accompanied by stickiness.
How to know it is this one
Wipes off with a damp cloth, unlike any true leaf disease.
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