- Rice weevil preparing to lay eggs on grain
© State of Queensland
Adult is 3-4 mm in length with a snout. Varies from reddish-brown to nearly black with four light reddish or yellowish spots on its back.
Granary weevils, maize weevils.
Cosmopolitan, established in all regions except the coolest temperate regions. In Australia, this pest occurs in all grain-growing regions.
Major, widespread, regular. A primary pest of stored grain.
A major pest of whole cereal grains but also infests cereal products such as pasta.
Larval feeding leaves large cavities inside grain and emerging adults leave large emergence holes. Adults feed on the damaged grains and large numbers produce heat and moisture, encouraging mould growth and mites, both of which reduce quality.
Adult weevils live 2-4 months, do not readily fly but will climb vertical surfaces. Each female lays 300-400 eggs during its lifetime. Eggs are laid singly in holes dug in grain and covered with a waxy plug by the female; larva grows inside the grain, excavating a cavity as it grows and pupates inside it.
The total development from egg to adult takes about 25 days at optimal conditions of 30ºC and 70% relative humidity but this period is greatly prolonged during cold weather.
Commercially available pitfall and probe traps can either be placed on the grain surface or inserted into the grain bulk. Acoustic detectors and X-ray photography are also available commercially to monitor the developing stages feeding inside the grain.
- Pests of field crops and pastures: identification and control, editor P T Bailey.