Citrus yellowing: separate iron lock, root rot and huanglongbing
New-leaf yellow with green veins is not the same as a blotchy infected leaf.
- Citrus new-flush yellow.
- Sometimes even, sometimes one limb, sometimes bad roots.
- Three photos: flush, tree, root.
- Nitrogen shortage yellows old leaves first; iron lock yellows new leaves first.
- Huanglongbing is often mottled, with small crooked fruit — a plant-protection office must confirm. Iron lock is more even, veins green.
- Don’t treat every yellow as iron; don’t spray iron while huanglongbing is on the table.
- Foliar chelated iron: Follow the pack, repeat a few times. First aid only on the iron-lock path
- Name what you see before you feed.
- If leaves, roots and the surface disagree, stop.
What you see in the field
Citrus new-flush yellow. Sometimes even, sometimes one limb, sometimes bad roots. Three photos: flush, tree, root.First the leaf position: new or old, even yellow or between the veins. If that does not match, do not fertilise yet. Pull one plant and read whether the roots are white, brown or foul.
Tap to enlarge. The caption says what to photograph. Missing field photos are marked as to-be-added.
Why it looks like this
The field looks like this because the root cannot take water or nutrients the usual way. Fix the soil condition first — drainage, salt, acidity, compaction or a salt of fertiliser — then a thin feed. Rates live in the range on this page; confirm with a local station and the label.
Easy to mix up
Looks like “Nitrogen shortage”
Nitrogen shortage yellows old leaves first; iron lock yellows new leaves first.
Looks like “Huanglongbing”
Huanglongbing is often mottled, with small crooked fruit — a plant-protection office must confirm. Iron lock is more even, veins green.
Do this / don’t do that
- 1Compare the worst plants with a neighbour ridge. Photograph whole plant, close-up and soil surface before you add fertiliser.
- 2Match roots, leaves and the soil surface to this guide. If they do not line up, do not copy a bag count.
- 3Use the rate range on this page only as a range. Confirm with a local station and the product label.
Don’t do this first
- Don’t treat every yellow as iron; don’t spray iron while huanglongbing is on the table.
Rate range
Foliar chelated iron
Follow the pack, repeat a few times
First aid only on the iron-lock path.
Organic manure (tree basin)
Rotted, in a trench
Change the root zone.
These are ranges. Confirm with your local extension station and the product label.
When you see Citrus new-flush yellow. Sometimes even, test. Walk an S and mix — one hole is not the field.
Lesson video
2026-03-26 · Li Zeyu · For learning. Serious damage: local agronomist or a soil test.
For learning only. Fertiliser and pesticide decisions need a local agronomist and a soil test.
Not sure? Photograph the field to identify the problem