How to prevent post-harvest rind disorders in citrus
Many issues originate from pre-harvest factors such as nutritional imbalance, irregular irrigation, harvest timing, and climate during fruit growth.
6 different rind disorders and how to manage them
- Pitting
Pitting appears as small sunken areas on the fruit surface, typically after packing and/or cold storage. It results from membrane disintegration and oxidative stress in flavedo cells triggered by water loss or temperature/relative humidity fluctuations. Dehydration and mechanical stress destabilise membrane lipids and oil glands, causing localised collapse.
Management tip: Avoid rapid cooling or storing below the recommended temperature immediately after harvest.
- Rind breakdown
Rind breakdown involves general softening and brown collapse of the albedo and is non-pathogenic; this is associated with senescence-related cell wall enzyme activity and the loss of integrity. Fruit with low Ca and B, or with excessive N, are more susceptible, and delayed harvesting may exacerbate the disorder.
Management tip: Maintain adequate Ca and B levels; avoid excessive N before harvest.
- Chilling injury
Chilling injury occurs when storage temperatures drop below cultivar-specific thresholds. Low temperatures alter the composition of membrane lipids, leading to electrolyte leakage and cell death. Symptoms include brown staining, surface pitting, and peel collapse.
Management tip: Store fruit above cultivar-specific minimum temperatures (usually 5–8 °C).
- Anthracnose
Anthracnose, caused mainly by Colletotrichum gloeosporioides, is often observed post-harvest from latent field infections and is favoured by senescent or nutritionally stressed tissues.
Management tip: Apply pre-harvest fungicide sprays where field infections are known to occur and avoid late N applications.
- Oleocellosis
Oleocellosis is a physiological oil-spotting disorder caused by the rupture of oil glands in the flavedo; phytotoxic essential oils burn the surrounding tissues. The risk increases when fruit are harvested when turgid and wet or handled roughly.
Management tip: Delay harvesting for 24–48 hours after heavy rain or irrigation to reduce turgor pressure; avoid rough handling.
- Creasing
Creasing is a physiological disorder characterised by depressions or folds on the rind linked to excessive cell enlargement and the weakening of albedo/flavedo tissues; it develops pre-harvest and can intensify post-harvest with water loss. Creasing has been associated with fluctuations in fruit turgor, high N:Ca ratios, and imbalanced growth regulators such as gibberellins
Management tip: Maintain stable irrigation, avoid excessive N, and ensure adequate Ca throughout fruit development to strengthen rind cell walls.
Read the full article (and browse for other sub-tropical related articles) in Issue 8 of our ROOTED e-mag here: https://duroinursery.co.za/media/
