Greybanded leaf weevil
Photo by Andrew Weeks, Cesar Australia
Greybanded leaf weevils are a sporadic pest of canola and lupins. The grub-like larvae are commonly found in high numbers on marshmallow weed.
Greybanded leaf weevils are sporadic pests that have a widespread distribution in eastern Australia. They have been reported across the southern cropping region in New South Wales, South Australia, Victoria and Tasmania.
Greybanded leaf weevils have been reported in New South Wales, South Australia, Victoria and Tasmania.
The adult weevils are approximately 8 mm long and light brown-grey in colour. They have distinctive raised markings (bumps) and a paler colour banding on the rear of the abdomen, covering approximately 1/4 of the elytra (wing covers). Adults are thought to be flightless. Larvae of the greybanded leaf weevil are legless, up to 5 – 8 mm long and yellow-green in colour with a darker coloured head.
Little is known about the lifecycle of greybanded leaf weevils. Eggs are laid on plant leaves, after which the larvae emerge in autumn/winter and feed on plant leaves before pupating in the soil.
Because larvae are legless, natural dispersal can be slow. However, greybanded leaf weevil adults and larvae have a tendency to move into crops from weed hosts growing along fence lines that die off after herbicide applications. Larvae are often observed feeding on plant foliage.
Similar to Top
Adults are similar to other weevils, including the vegetable weevil and spotted vegetable weevil. Larvae are similar in size and colour to vegetable weevil larvae.
Crops attacked Top
Canola and lupins. Malvaceous weeds such as marshmallow are also a favorable host plant.
Typical weevil damage includes leaf scalloping, chewing of leaf edges and thinning of plants. In severe cases, canola cotyledons can be completely chewed off at ground level. Weed hosts such as marshmallow can be severely defoliated.
Check crops during establishment, especially near fence lines and areas in paddocks where marshmallow weed is present or was growing prior to sowing. Shot holes in the leaves of marshmallow plants are a key indicator of the presence of greybanded leaf weevil larvae.
Economic thresholds Top
There are no economic thresholds established for this pest.
Management options Top
There are no known biological control agents for greybanded leaf weevils.
Control summer and autumn weeds, particularly marshmallow, to reduce the availability of alternate hosts between growing seasons.
Controlling summer/autumn weeds near crops, especially marshmallow weed, can reduce populations of grey-banded leaf weevils.
There are no insecticides currently registered to control greybanded leaf weevils. There are field reports that suggest synthetic pyrethroids used at 400 mL/ha against other pests may also provide control of greybanded leaf weevil. Check the APVMA website for current chemical options.
This article was compiled at cesar by Alana Govender and Paul Umina.
References/Further Reading Top
Bellati J, Mangano P, Umina P and Henry K. 2010. I SPY Insects of Southern Australian Broadacre Farming Systems Identification Manual and Education Resource. Department of Primary Industries and Resources South Australia (PIRSA) and the Department of Agriculture and Food Western Australia (DAFWA).
Cribb M and Umina P. 2013. Crop Weevils: The Back Pocket Guide. GRDC and cesar.
|February 2016||1.0||Alana Govender (cesar) and Paul Umina (cesar)||Garry McDonald (cesar), Bill Kimber (SARDI)|
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