Wireworms

Large numbers of (true) wireworms and associated feeding damage have been reported in various tillering wheat crops in NSW, but control is difficult

 

Where have they been reported?

Large numbers of (true) wireworms and associated feeding damage have been reported in various tillering wheat crops near Condobolin in NSW’s Central West Slopes. Many plants are experiencing tiller yellowing and death. The damage has been observed right across the paddocks and attempts at control have proved difficult.

Wireworm habits and behaviour

Wireworms (Family: Elateridae) are the larvae of several species of Australian native beetles, commonly called ‘click’ beetles. In addition to cereals, wireworms attack oilseeds and grain legumes. 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.

Wireworm larvae feed exclusively in the soil on seeds and bore into the underground stems of cereal plants. They may also damage the roots of young plants or ring-bark and/or sever the hypocotyl just below the soil surface. Plants of affected tillers wither and die resulting in a thinned crop or bare patches.

Our advice

Early identification and detection of true (and false) wireworms is important before sowing. Once feeding damage has become obvious it is often too late to implement effective control. At this stage of the season, control with insecticides is particularly challenging because the chemical is unlikely to leach through the soil and come in contact with wireworms. Foliar applications may be used for partial control of some species of false wireworms that feed above ground, but not true wireworms.

Control options

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. The use of a press wheel during sowing will limit access of wireworms to emerging seed. Insecticidal seed dressings and in-furrow treatments offer some protection from moderate larval numbers.

Description

Wireworm 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 and their abdomen is terminated with a flattened, serrated tail-piece above a single proleg. Adult beetles are small- to medium-sized beetles with elongated, flattened bodies that have blunt rounded ends. Wireworms are often confused with another group of beetles called false wireworms (Family: Tenebrionidae).

 

*Source of field reports of wireworms

Olivia Wright – Agronomist, AGnVet Services (NSW Central West Slopes & Plains)