Photo 1. Extensive damage on leaves of bele by Nisotra basselae, such that growers in many parts of Solomon Islands have abandoned its cultivation.
There is no common name, but bele flea beetle, Abelmoschus flea beetle, aibika flea beetle sliperi kabis flea beetle would all be suitable.
Narrow. The beetle is endemic to Papua New Guinea, and in 1984 spread to Solomon Islands.
Bele (aibika, sliperi kabis, island cabbage, Abelmoschus manihot), possibly Hibiscus tilaceous (under lab conditions, but not seen in the field); not on Sida, nor the garden hibiscus, Hibiscus rosa-sinensis.
Adult beetles feed on leaves creating many small (1-5 mm diameter) holes (Photo 1). Eggs are laid singly or in small batches just below the surface of the soil, near the stem. They hatch after 8-9 days, and the larvae remain in the soil for 12-18 days feeding on small roots. They moult twice before they pupate for 4-6 days. Adults emerge from the soil (Photo 2). Males emerge first, taking 6-8 days to become sexually mature; females take 3-5 days. The entire life cycle takes about 40 days (Diagram). The adults disperse by walking, jumping and flying. The number of generations per year is unknown.
The damage is so severe that in many places in Solomon Islands people have stopped growing bele. The larvae feed on small roots, especially the tiny root hairs. Whether this affects the growth of the plant is unknown.
Look for small holes in the leaves and the presence of beetles. The adult beetles are about 4 mm long and can be found on both sides of the leaves. The head and part of the section below are orange/brown, and the wing cases are black. The beetles are less obvious during the hotter times of the day, when they move under the leaves.
Some of the more isolated parts of the Solomon Islands are free from the beetle, e.g., the provinces of Rennell and Bellona, and Temotu. Therefore, no leaves of bele or other parts of the plant should be taken there. Extension services should constantly remind people of this, with messages on radio and in newspapers.
Parasites of the adults include nematode worms and mites. The adults do not seem to be affected by the presence of the fire ant, Wasmannia auropunctata. Nisotra may be toxic to visual predators, like birds and lizards.
There are a number of possibilities:
AUTHORS Helen Tsatsia & Grahame Jackson
Information (and Diagram) supplied by Maclean Vagalo, Entomologist, SPC, and Chris Reid, Principal Research Scientist, Entomology, Australian Museum, Sydney.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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