Spotted vegetable weevils

Agronomist, John Jervois (Tarcutta Rural), has reported adult weevils attacking an emerging wheat crop near Tarcutta, in the South West Slopes district of New South Wales. The weevils appear to be spotted vegetable weevils (Steriphus diversipes), which are often referred to as the Desiantha weevil. The affected crop is at the 3-4 leaf stage.

The spotted vegetable weevil is a sporadic pest and widely distributed across New South Wales and Victoria. Adults are mottled grey-black weevils with grey flecks on the abdomen. They grow up to 7 mm long. Larvae are white with orange-brown heads, and grow to 8 mm in length. The larvae are soil dwelling.

John says the weevils have caused considerable damage, chewing seedlings down to the ground and scalloping leaf edges. Adult spotted vegetable weevils rarely feed on cereals, however the affected paddock was previously pasture. This likely provided favourable hosts such as capeweed and grassy weeds, and facilitated the build up of weevil populations. John reported highest numbers were observed in parts of the paddock that had a thick dead layer of wireweed and sorrel trash. Although difficult to accurately estimate densities, John says he was typically finding 2-3 adult weevils within a metre square.

Crops that follow a long-term pasture are most likely to be at risk of spotted vegetable weevils. Inspect newly sown paddocks and germinating seedling crops, looking for poor emergence or bare patches. There are no foliar insecticides registered against this species. Seed treatments can reduce the feeding damage to cereal seedlings. There are reports in WA that suggest insecticides used against the vegetable weevil may also provide control of spotted vegetable weevils.

For further information on weevils download the GRDC Back Pocket Guide - Crop Weevils.