False wireworms and true wireworms

There have been several reports of false wireworms (F: Tenebrionidae) and true wireworms (F: Elateridae) across several regions of Victoria and New South Wales. Agronomic Consultant, Luke Maher (AgriVision), has observed false wireworm larvae in a number of canola paddocks around Swan Hill, in the Mallee district of Victoria. Luke says the feeding damage across paddocks is sporadic and generally not severe. Paddocks with heavier soil types and high amounts of stubble are most affected.

We have identified true wireworm and false wireworm larvae for Research Officer, Greg Davis (AgriTech Crop Research), from a canola crop north of Grenfell, in the Central Tablelands district of New South Wales. True wireworm adults were also found in the paddock. Greg reports finding 1-2 individuals/metre row, however only minimal feeding damage to plants has occurred. District Agronomist, Joanne Holloway (I&I NSW), has also observed true wireworm adults in a wheat paddock north of Wagga Wagga, in the Riverina district of New South Wales.

False wireworms attack a variety of crops including cereals and canola, and are mostly found in paddocks with high amounts of stubble and trash. There are a large number of false wireworm species, which are similar in appearance. The most common broad-acre pest species in Victoria and New South Wales are the grey false wireworm, the eastern false wireworm, the bronzed field beetle and the vegetable beetle.

False wireworm larvae are relatively fast moving, have a pair of prominent spines on the last body segment and vary in colour from cream-yellow to brown-grey. They generally grow between 10-50 mm long, and have a hardened cylindrical body. False wireworms attack germinating seeds and chew on seedling stems and roots, weakening the plant or ring-barking the plant.

True wireworms are the larvae of several species of Australian native beetles commonly called ‘click’ beetles. The adults are small- to medium-sized beetles with elongated, flattened bodies that have blunt rounded ends. Larvae grow between 15-40 mm in length, are soft-bodied, flattened and slow moving. Their body colour ranges from creamy yellow in the most common species to red brown; their head is dark brown and wedge-shaped.

True wireworms feed on underground roots, seeds and stems. They attack pre- and post-emerging seedlings of all oilseeds, grain legumes and cereals. Like false wireworms, problems with true wireworms are often associated with stubble retention and trash from previous crops, which is believed to provide a refuge that favours survival and breeding.

Early identification and detection of true and false wireworms is important. Once damage has become obvious it is often too late to implement effective control. Foliar applications can be used for partial control of some species of false wireworms that feed above ground. In paddocks with a history of wireworm problems, cultivation before seeding may reduce pest pressure. Rotations, including continuous cropping or short pasture phases often limit population increases, while insecticide seed dressings can also offer some protection.

It is important to be aware that once crop plants are advanced they will be able to out-grow moderate numbers of both true and false wireworms.

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