Collections of the red mangrove, Rhizophora mangle, were made at three of six survey sites in Fiji – Suva, Beqa and Ovalau – with 40-70% of the leaves showing small, chlorotic spots, occasionally coalescing to form light blotchy areas. The plants appeared to be in good health, though some of the new leaves were small and slightly distorted.
R. mangl has New World origins and in the south west Pacific is only found in Samoa, Tonga, Fiji and New Caledonia.
No one on the list knew of the identification of the leaf spot. It was suggested that USP, Suva, the University of Hawaii and the University of Hong Kong be contacted; the latter has published on the fungi of mangroves in Mycological Research.
An alternative suggestion was that the symptoms were typical of saliva toxicity from feeding by some sort of scale insect/aphid/whitefly. Diaspididae, in particular, can cause yellowing of the leaf lamina in the immediate vacinity of the stylets and under dense colonies (e.g. Pinnaspis strachani has been found feeding on Rhizophora mangle in the South Pacific).
Stunting and distortion of young leaves can also be caused by Sternorrhyncha feeding, e.g. by aphids or whiteflies.