iron-deficiency chlorosis

Symptoms

Yellow leaves with green veins (interveinal chlorosis).

Easily confused with

• citrus greening (Huanglongbing, HLB)

  How to tell them apart: On citrus, both yellow the leaves but only one is a quarantine emergency. Iron/zinc deficiency (abiotic): SYMMETRIC interveinal yellowing, mirrored on both sides of the midrib, green veins, no fruit effect, corrects with feeding/pH fix. Huanglongbing / citrus greening (Candidatus Liberibacter asiaticus, EU quarantine, NOTIFIABLE): ASYMMETRIC blotchy mottle that crosses the midrib unevenly, corky/yellow veins, and small lopsided fruit that stay green at the bottom and taste bitter - if the mottle is blotchy and asymmetric, treat as SUSPECTED HLB and report it.

• two-spotted spider mite

  How to tell them apart: Two-spotted spider mite (Tetranychus urticae): look on the UNDERSIDE of leaves for very fine pale stippling — a sandblasted, finely dotted pattern of tiny chlorotic specks evenly scattered across the whole blade, including over the veins. Affected leaves turn dull, bronzed and dusty-grey, and you will find fine silken webbing in leaf axils and tip clusters plus moving pinhead-sized mites (often with two dark body spots). Damage is worst in hot, dry, dusty conditions and on older, sun-exposed leaves. Iron-deficiency chlorosis (abiotic_chlorosis_iron) is completely different: it shows uniform interveinal yellowing on the YOUNGEST leaves while the veins stay sharply green (a green net on a yellow leaf), with no stippling, no bronzing, no webbing and no mites; it is symmetrical, linked to alkaline/waterlogged soil, and the leaf surface stays smooth.

• cotton aphid

  How to tell them apart: Iron-deficiency chlorosis (abiotic_chlorosis_iron) turns the youngest hibiscus leaves uniformly pale yellow while the veins stay distinctly green — a clean interveinal net — with no insects, no stickiness and no leaf distortion, and it is symmetric across the whole new flush, worsening on alkaline or waterlogged soil. Cotton aphid (Aphis gossypii) instead shows soft yellow-green to dark sucking insects in colonies on shoot tips and leaf undersides, with sticky honeydew, black sooty mould and patrolling ants; the yellowing is blotchy and the new leaves are curled, cupped or stunted rather than evenly greenscreened. Turn a yellow shoot over: bare undersides with a crisp green-vein pattern point to iron; clustered aphids and gloss point to Aphis gossypii.