Porter Novelli Adelaide

 

  

Key points:

• Growers urged to check for Mandalotus weevil in germinating crops
• Late-sown crops in Mallee district particularly susceptible

Growers are being advised to check for Mandalotus weevils in germinating crops, particularly those sown later on rubbly or lighter calcareous soil types.

This follows the identification of Mandalotus weevils in seedling canola crops at Rupanyup and Sea Lake in Victoria and at Minlaton and in the Mallee in South Australia.

At Rupanyup in the Victorian Wimmera district, about one-third of a 40 hectare paddock was affected and about 5-10 per cent was destroyed, according to the PestFacts electronic newsletter services which are supported by growers and the Australian Government through the National Invertebrate Pest Initiative (NIPI), a project funded by the Grains Research and Development Corporation (GRDC).

Researcher and PestFacts SA and Western Victoria co-ordinator, Kym Perry (South Australian Research and Development Institute Entomology), said adult Mandalotus weevils were 3-5 millimetres long, round and dull brown in appearance, resembling small clods of dirt.

“They are known to attack canola, cereals, beans and medic pasture,” Mr Perry said.

“Adults actively feed during the night, while during they day they can be found hiding under clods of dirt and trash.

“In severe cases, seedlings can be ring barked just above ground level, causing them to fall to the ground where the weevils continue feeding on the leaves.”
 
Mr Perry said it was possible that healthy plants may be able to outgrow damage caused by weevils.

Currently there are no registered insecticides for control of Mandalotus weevils. The GRDC is currently investing in a number of projects investigating a range of control measures and possible chemical controls for this pest. 

The distribution and host range of Mandalotus appears to have widened in southern Australia in the past few years and population increases are probably a direct result of minimum tillage practises where stubble creates a more favourable weevil habitat.

Mr Perry said little was known about the biology of Mandalotus weevils, so grower observations and information were extremely valuable to the PestFacts service.

“We would appreciate any specimens being sent to us, along with estimates of economic damage, for research purposes,” he said.

SARDI’s Entomology Unit and CESAR Consultants offer a free insect diagnostic service for PestFacts subscribers.

To report Mandalotus weevil sightings or to subscribe to PestFacts, contact SA and Western Victoria co-ordinators Kym Perry on (08) 8303 9370 or email perry.kym@saugov.sa.gov.au, or Ken Henry on (08) 8303 9540 or email henry.ken@saugov.sa.gov.au, or PestFacts South-Eastern co-ordinator Stuart McColl on (03) 9329 8816 or email stuart@cesarconsultants.com.au. 

Growers can find more information about pests and their management by visiting www.grdc.com.au/pestlinks.