September 2005. From Tahiti, French Polynesia, photos of a skin necrosis of coconuts from a semi-dwarf palm. The necrosis begins on very young nuts with some bleaching. The tree is isolated, in an urban area, with high ground water. According to the owner, the fruit had been healthy until the part of the frontyard around the coconut tree was cemented last June.

The damage looks similar to that of the coconut Eriophyid mite Aceria guerreronis Keifer, which is not thought to be in Tahiti. According to the CABI Crop Protection Compendium: Populations of the mite develop on the meristematic zone of the young nuts, from as early as one month after fertilisation. This area is covered by the perianth (collectively, the tepals, and often referred to as the bracts). Feeding of the mites in this zone apparently causes physical damage so that as newly formed tissue expands, the surface becomes necrotic and suberized, usually in distinct “V” shape(s) extending down from the perianth. Uneven growth results in distortion and stunting of the coconut; usually the younger the nut when first attacked the greater the severity of damage.

However, although it matches the CAB diagnosis and, if it is this mite then it is very serious, it would be useful to know the history of the tree – if there is any suggestion is was imported (out of quarantine). It might be best to destroy it immediately. Look for the cause in the very young nuts – including sucking bugs (Hemiptera) – maybe at night – and other mites.

Members recommended the need for proper identification of the mite before any quarantine measures were taken.