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Sigastus weevil - an emerging pest of macadamias in north Queensland

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Fay, H.A.C., De Faveri, S. G., Storey, R.L. and Watson, J. (1998) Sigastus weevil - an emerging pest of macadamias in north Queensland. In: Proceedings of the Sixth Workshop for Tropical Agricultural Entomologists, May 1998, Darwin, Australia.



A large weevil was found infesting macadamia nuts on the Atherton Tableland during the 1994/95 season. It was unrepresented in various Australian insect collections but thought to belong to the genus Sigastus. This paper reports some preliminary studies on its biology, pest status and control. From 4-6 weeks after first nut-set adult females commence laying single eggs through the husk, after first scarifying an oviposition site. The nut stalk is then cleaved leading to rapid abscission. Nuts were generally attacked up until hard shell formation. Weevil larvae consumed whole kernels, with % survival higher and larval duration shorter in larger nuts. Infestation rates increased with increasing nut diameter, reaching 72.8% of fallen nuts by mid-October. A crop loss of 30% could be attributed to weevils in an unsprayed orchard. However, adult weevils are very susceptible to both carbaryl and methidathion sprays. In addition, exposure of infested nuts to full sunlight over several weeks kills 100% of larvae. Crops should be surveyed for weevil damage from the 5-10 mm diameter stage until mid-December. Methidathion used as an initial spray for fruitspotting bugs should provide control. Organic growers are advised to sweep infested nuts into mown interrows where solarisation will kill larvae.

Item Type:Conference or Workshop Item (Paper)
Business groups:Crop and Food Science, Horticulture and Forestry Science
Additional Information:© The State of Queensland
Keywords:Macadamias; Sigastus; weevil; control.
Subjects:Plant pests and diseases > Pest control and treatment of diseases. Plant protection
Science > Zoology > Invertebrates > Insects
Plant culture > Fruit and fruit culture > Nuts
Plant pests and diseases > Individual or types of plants or trees
Live Archive:09 Aug 2004
Last Modified:13 Dec 2021 02:57

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