Citrus decay control is won in the first six hours after picking, not in the reefer. Three organisms cause most of the loss on Egyptian citrus shipments: green mould, blue mould and sour rot. All three enter through wounds in the rind, and all three are effectively unstoppable once the fruit is inside a sealed container. What follows is where each one starts, which one you see after a long cold voyage, and the steps that actually change the outturn.
The three organisms and how to tell them apart
| Decay | Organism | Appearance | Behaviour in cold transit |
|---|---|---|---|
| Green mould | Penicillium digitatum | Olive-green spore mass, wide white margin | Slows markedly below 5 C, resumes on arrival |
| Blue mould | Penicillium italicum | Blue-green spores, narrow white margin | Grows at lower temperatures, so it dominates long cold voyages |
| Sour rot | Geotrichum candidum | Watery collapse, cream slime, sour smell | Slow when cold, explosive once warm |
The practical distinction matters for diagnosis. A container that arrives with predominantly blue mould has usually run cold and long. A container full of green mould more often points to a break in the cold chain or a warm hold before loading. Sour rot points at overmature fruit, standing water or a contaminated dump tank, and it spreads by contact from fruit to fruit inside the carton.
Infection starts with a wound
Penicillium spores are present in every orchard and every packhouse. Intact rind resists them. Injured rind does not. The wounds that matter are made at harvest by pulling fruit instead of clipping it, by long stems that puncture neighbouring fruit, and by long fingernails on picking crews. More are made on the line by drops of more than about 15 centimetres onto hard surfaces and by rough brush rollers. Every one of those is a control point that costs nothing to fix and pays back in reduced arrival decay.
The packhouse controls that change the outturn
Sanitation of the dump tank and drench water comes first, because contaminated water inoculates every fruit that passes through it. Fungicide is normally applied in the wax coating, and the choice is constrained by the destination market: the active substance has to be approved there and the residue has to sit inside the applicable maximum residue level. Confirm both before the season rather than after a rejection. What the coating does and what to specify is covered in our note on waxing and coating on Egyptian citrus.
Speed is the other control. Fruit that goes from field to cold store within 24 hours carries far less inoculum load than fruit that sits overnight in a warm shed. Cull rigorously at the grading table, because one sour rot fruit will take the cartons around it. Documentation for the shipment, including the phytosanitary certificate, does not substitute for any of this; a certificate confirms pest freedom, not decay resistance.
Nile Prime is the exporter, not an independent laboratory. Treatment options depend on what is registered and permitted in the destination market, and nothing here should be read as approval to apply a specific product.
To review a decay problem on an arrived container, or to agree the treatment and residue position for a 2026/2027 citrus programme, message Nile Prime on WhatsApp at +20 10 9911 1918.