?Boron deficiency Minimize

September 2002. A papaya fruit rot from Palau, showing distortion, ridges, dripping latex and internal rot.

There were several suggestions:

  • Wind damage: there has been much wind damage in the last two months and the fruits have suffered physical damage, followed by fungal and bacterial decay.
  • Cladosporium herbarum: the description of the disease in A colour atlas of post harvest diseases of fruit and vegetables, by Snowdon, says ' the disease is known as internal blight in Hawaii because the fungus invades the seed cavity causing it to become dark and dry. Infection occurs via the flower end and the eventual effect is normal ripening is prevented. This seems to match the symptoms shown in the photo'.
  • Boron deficiency: lumpy misshapen fruit with extrusion of of latex. Look also at the stem just back from the growing point, where there may be dark cracks 3-4 mm long and hardened latex 'drips'. If it is boron deficiency, it tends to be a bit seasonal and fruit can look pretty bad at some times of the year and normal in others.
Boric acid is normally applied as a spray to get a quick response as uptake rates from soil may be quite slow. There is the chance of boron toxicity if too much is added. A rate of 0.3% borax was suggested, plus wetting agent.

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