Yellowheaded cockchafers

Outbreaks of yellowheaded cockchafers appear to have spread to new areas in the Southern Tablelands of NSW; there are very limited options once crops are planted

Yellowheaded cockchafer larva (Source: cesar)

 

Where have they been reported?

Yellowheaded cockchafers have spread to new territory this year around the Goulburn area of the Southern Tablelands of NSW. In past years, yellowheaded cockchafers were largely confined to crops and pastures on red soils north of Goulburn, however, this year they have become much more widespread, also occurring on pastures and cereals on sandy loam soils.

About this pest

Yellowheaded cockchafer (Sericesthis harti) is the main species of white curl grub affecting cereal crops across south-eastern Australia including NSW, Vic and SA. Larvae are “C” shaped, creamy-grey in colour and have a yellow head capsule. When fully grown in winter they are about 25-30 mm long. Larvae live in the soil until mid-late summer when they emerge as adult beetles. Adult beetles achieve long distance dispersal by flying, usually at dusk on warm evenings in late spring-early summer, hence adults are able to colonise new territory. 

For detailed information on yellowheaded cockchafer, including their occurrence, lifecycle, behaviour, damage symptoms and preventative management strategies, go to yellowheaded cockchafer.

Our advice

Control of yellowheaded cockchafers relies on forward planning. Cereal crops following several years of pasture are most susceptible. Unfortunately, once crops are sown little can be done to reduce populations because the larvae do not come to the surface to feed. Growers often apply high rates of chlorpyrifos immediately prior to rainfall events in the hope of ‘leaching’ the chemical through the top soil layer. However, in the vast majority of cases this approach will not provide adequate control of yellowheaded cockchafer larvae.

Intensively grazing in spring, summer and autumn will make eggs and larvae in the topsoil more susceptible to desiccation and predation by birds. Spring-prepared fallows will help reduce damage in the following year. Intensive crop rotations and short pasture rotations can also be used to prevent future damage. Cultivation will directly kill larvae and expose them to predation. Seed treatments may eventually be an option: there is a new registration of a mixed formulation product against cockchafers in other crops but not cereals.

Re-sowing affected areas with a higher seeding rate will assist plant establishment.

 

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Sources of field reports of yellowheaded cockchafers

Julian Minehan – Agronomist, Landmark (NSW Southern Tablelands)