Sightings of vegetable beetles indicate impending false wireworm presence

Vegetable beetles can damage crops in their own right. They will have also layed eggs through autumn, so false wireworm larvae may become an issue in winter

The vegetable beetle (Source: cesar) (left) and its larval form, the southern false wireworm (right) (Source: SARDI)

 

Where have they been reported?

Vegetable beetles, the adult form of the southern false wireworm (Gonocephalum spp.), have been observed in crops in Victoria’s Northern Country and South West districts. In a canola crop, planted on clay loam soil and containing both pea hay and barley stubble, plants had been observed with cotyledons either chewed or completely removed, leaving stems just below the soil surface. In this case, native cockroaches were also present and it is likely that both invertebrates had contributed to the damage. 

About vegetable beetles

Vegetable beetles are generally 6 – 8 mm long and 3 mm wide, dark grey-black in colour and often mottled or covered in soil. Females will usually lay their eggs near a food source in autumn.

Their larvae (southern false wireworms) are soil swelling and have cylindrical elongated bodies that are cream-yellow or tan in colour. They generally feed on winter cereal crops, and can sometimes hollow out cereal seeds.

Adult beetles generally feed on decaying vegetable matter, however in some situations they will attack emerging winter or spring-sown canola crops or lupins. They are capable of chewing plants above ground, ring barking or completely cutting stems.

For more detailed information about these pests, and for further advice on preventative strategies, go to southern false wireworm within the PestNote series.

Our advice

Controlling vegetable beetles is difficult at this time of year as they can tolerate high rates of many insecticides. Cultural methods such as suitable crop rotations and clean cultivation over summer may be the best means of preventing the build-up of both adults and larvae in problem areas. For example, raking stubble has been found to reduce vegetable beetle numbers more effectively than the use of insecticides; burning the stubble is another effective option.

Chlorpyrifos is registered as a foliar spray against false wireworms in certain broadacre crops in some states. Insecticide seed dressings are registered against false wireworms in canola and other crops.

 

Sources of field reports of vegetable beetles

Bronwyn Hunt – Grower, Merriwa Pastoral Company (Victoria’s Northern Country)

Twitter sources:

Ben Dumesney (‪@BenDumesny)