Whitefringed weevils

Agronomist, Nathan McIntosh (GrainCorp), has reported weevils attacking an established lucerne paddock near Parkes in the Central West Slopes and Plains district of New South Wales. Based on the description of the weevils and damage being caused, it is likely that they are whitefringed weevils (Naupactus leucoloma), a common pest of lucerne in many parts of southern Australia. The weevils are present in high numbers (10-20 per plant) and have destroyed approximately 40 acres of a 50-acre paddock. The adults have been chewing the lucerne crowns and the larvae are attacking the plant roots. Given the severity of the infestation, some form of intervention is necessary and control options are now being considered. There are currently no insecticides registered to control whitefringed weevils in lucerne.

District agronomist, Phil Bowden (NSW DPI), has also reported observing whitefringed weevils in several lucerne padocks around Cootamundra in the South West Slopes district of New South Wales. Phil says they can be easily found at the tops of stems chewing on leaves, however the lucerne is well established and growing quite vigorously after recent rainfall, which, combined with periodic grazing, appears to be enough to avoid significant damage. Whitefringed weevils were also identified in samples from lucerne paddocks in similar regions of New South Wales in March and April this year.

The larvae of whitefringed weevils are fat, legless grubs that live in the soil and feed predominantly on the tap-roots of plants, generally from late autumn to early summer. They have a yellowish body with a light-brown head and can be up to 13 mm long. Larvae can cause significant damage to plant root systems, reducing the productivity of crop plants. Crops likely to be attacked include lucerne, pastures and some pulses.  

Adult whitefringed weevils grow to about 15 mm long and have a short, downward pointing snout. They are grey-brown in colour with a characteristic white stripe running along either side of the body. Adults emerge from the soil in summer and feed on plant foliage producing characteristic notched or saw-toothed edges. Damage to plants caused by adult weevils is usually minor compared with that caused by larvae.

Click here for images of whitefringed weevils.