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May 2000. Sugarcane weevil borer, possibly Rhabdoscelus obscurus, is a problem in several Pacific Island countries as well as Australia. Photos were sent for ID from Northern Marianas Islands.
The weevil started to create problems for the palm nursery industry in north Queensland, following an increase in green cane harvesting in the sugar industry and use of sugar cane bagasse in potting mixes and as mulch. A wide range of palms are known to be hosts of sugar cane weevil borer, including the betel-nut palm. Some good background information on this problem can be found in:
Halfpapp KH, Storey RI (1991) Cane weevil borer, Rhabdoscelus obscurus (Coleoptera:Curculionidae), a pest of palms in northern Queensland, Australia. PRINCIPES 35:199-207.
The tachinid parasite of R obscurus, Lixaphaga sphenophori, was introduced from PNG to Australia early last century, but does not exert sufficient control on weevil borer in palms in the majority of situations. Therefore, chemical and cultural treatments against weevil borer have been developed for the nursery industry. These include:
1) application to run-off of chlorpyrifos (5 -10ml/l of 500g/l ec) to the leaf bases, trunk and soil – two applications one month apart during major periods of weevil activity;
2) removal of old and dead fronds which shelter adult weevils;
3) destruction of heavily infested plants; and
4) cessation in the use of bagasse in potting mixes and as mulch.
Both prothiophos and bifenthrin were almost as efficacious as chlorpyrifos, and subsequently fipronil has been shown to have good activty against weevil borer, too, and is used in the sugar industry. Also,
there have been some relatively recent studies on the pheromones of palm weevils (including Rhabdoscelus) by Robin Giblin-Davis (University of Florida, Fort Lauderdale).
An online publication can be accessed at: Giblin-Davis, R.M. et al. (1996). Chemical and behavioral ecology of palm weevils (Curculionidae:Rhynchophorinae). FLORIDA ENTOMOLOGIST 79:153-167.
An aggregation pheromone is reported. See Pests>Pest Management>Chemical control>Pheromones.
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