False wireworms

Agronomist, Karla Whittaker (AGnVET Services), has reported false wireworms (Coleoptera: Tenebrionidae) attacking several crops near Boree Creek, in the South West Slopes of NSW. Karla reports that a wheat paddock, which was pasture last year, has suffered significant seedling mortality as a result of false wireworms. An established grass and clover pasture paddock has also recently been attacked, with feeding damage also occurring to capeweed.

False wireworms are the larval form of native beetles, some of which are known as pie-dish beetles. They normally live in grasslands or pastures and cause little damage in this situation. In crops, they are mostly found in paddocks with high stubble and crop litter contents. They may affect all winter sown crops.

There are a large and varied number of species, including the grey false wireworm, the eastern false wireworm and the southern false wireworm. The species are similar in appearance with larvae generally growing between 10-50 mm in length. Larvae are cylindrical, hard bodied, fast moving and golden brown to black-brown or grey in colour. They have pointed upturned tails or a pair of prominent spines on the last body segment.

False wireworms chew into the seedling stem and roots, weakening the plant or ring-barking the stem. The injury to the seedlings makes them susceptible to dehydration and infection by disease. Feeding damage is often most severe when germination is slowed by continued dry weather. There is evidence suggesting that stubble retention and minimum tillage are contributing to the build-up of false wireworm populations in south-eastern Australia.

Agronomist, Matthew Shephard (IMAG Consulting), has also reported problems in emerging linseed crops in the Central West Slopes and Plains district of NSW. Matthew says there are large patches of the paddocks where linseed seedlings have suffered significant root damage. This was first thought to be caused by false wireworm feeding, although no pests were uncovered upon digging in the affected areas. It is possible that this damage may not be caused by insect feeding, but rather the result of a plant disease. Matthew has sent samples to a crop pathology laboratory for testing.

This report serves as a timely reminder that continual crop monitoring and species identification are critical to making the right pest management decisions and avoiding unnecessary pesticide applications.