Pacific Pests, Pathogens and Weeds

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Summary

• Restricted. South and Southeast Asia, Oceania. In Australia, Fiji, New Caledonia, Papua New Guinea.
• Minor pest. Mostly rice, but also sedges. Damage worse if infestation after panicle initiation and flowering.
• Larvae bore into rolled leaves, and then through internodes to the growing point, killing it; stems pull out easily (‘deadhearts’). Panicles fail to emerge, or emerge with unfilled grain (‘whiteheads’).
• Eggs on underside of leaf; brownish-yellow larvae, becoming whiter, with reddish line along back. Adults white (males with four dark spots on each forewing). Strong flyers. Nocturnal.
• Natural enemies: many egg and larval parasitoids and predators.
• Cultural control: handpick in nursery; plough land well (burying larvae/pupae of previous crop); plant at higher density than normal; rotate, e.g., legumes; synchronise plantings with neighbours; submerge eggs by raising water occasionally; weed; apply split applications N; harvest at ground level to remove larvae; plough in stubble, unharvested plants and weeds; use resistant (short, high tillering, early maturing) varieties.
• Chemical control: unlikely to be needed. Use abamectin. Avoid broad-spectrum insecticides to preserve natural enemies.