Divisi
Citrus greening (Huanglongbing)
· Bacterial
Photo: T.R. Gottwald and S.M. Garnsey · Public domain
Citrus greening (Huanglongbing, or HLB) is a deadly, incurable bacterial disease of citrus trees — orange, lemon, lime, naartjie and grapefruit. The germ lives inside the tree's food-carrying veins (the phloem, the pipes that move sugars from the leaves) and slowly blocks them, so the tree starves from the inside. It is carried from tree to tree by a tiny sap-sucking insect, the citrus psyllid, and by grafting with wood cut from a sick tree. Once a tree has it, there is no cure.
Why it matters
Citrus greening is a death sentence for a citrus tree — there is no medicine that cures it, and a badly hit orchard can lose up to 100% (your whole crop). Long before the tree dies it turns your fruit small, lopsided, green-shouldered and bitter — unsellable and uneatable. It spreads silently: a tiny insect carries the germ from one tree to the next, and by the time you see the sick leaves, nearby trees are often already infected. Because you cannot cure it, your only real weapon is stopping it getting in and cutting out sick trees fast.
When to act
Any psyllids detected on new flush, or the first trees showing blotchy leaf mottling and lopsided bitter fruit; the disease anywhere in or near the orchard.
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full citrus greening (huanglongbing) field guide
- Identify it
- Scout for it
- Control it
16 field-guide sections in the app
The full guide to citrus greening (huanglongbing) — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
citrus
Frequently asked questions
How do I identify citrus greening (huanglongbing)?
The first thing you see: one branch or one side of the tree goes yellow while the rest stays green — a lopsided, one-sided yellowing, not the whole tree evenly. Look up into the canopy for these odd yellow shoots standing out against healthy green.
When should I take action against citrus greening (huanglongbing)?
Any psyllids detected on new flush, or the first trees showing blotchy leaf mottling and lopsided bitter fruit; the disease anywhere in or near the orchard.
How do I control citrus greening (huanglongbing)?
Prevent — start clean (your strongest defence): plant only certified disease-free young trees from a reputable nursery, and never graft with budwood (cutting wood) taken from a tree of unknown health. Most greening arrives on infected planting material or budwood — clean stock is the single biggest thing in your control.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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