Wireworms

Agronomist, Warwick Nightingale (Delta Agribusiness), has observed feeding damage in a tillering wheat crop near Jerilderie, in the Riverina district of New South Wales. Warwick says the youngest leaves are being chewed just below the soil surface, which is resulting in tiller death. Although minimal, the damage has been observed right across the paddock. These symptoms resemble the feeding damage of wireworms (Family: Elateridae), although Warwick says none could be found when directly searching. Traps have been now been established to identify the culprits.

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

In addition to cereals, wireworms attack oilseeds and grain legumes. It is reported that wireworm problems are often associated with stubble retention and trash from previous crops, which is believed to provide a refuge that favours survival and breeding. Wireworms are often confused with another group of beetles called false wireworms (Family: Tenebrionidae). False wireworms are common pests across southern New South Wales.

Early identification and detection of true and false wireworms is important. Pitfall traps are an effective monitoring technique that can be used to collect wireworms and other beetles. Once feeding 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 will often limit population increases.