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False wireworms

Agronomist, Craig Warren (Landmark), has reported false wireworms causing damage to several wheat crops situated north of Temora, in the South West Slopes district of New South Wales. Craig says many growers have experienced continued feeding damage in paddocks with self-mulching grey clay soils. In some paddocks, plant numbers have been reduced to as low as 60 plants per m2 as a result of false wireworm feeding. 

Agronomist, Steve Brabin (AGnVET Services), has also reported false wireworm issues across several wheat crops northeast of Junee, in the South West Slopes district of New South Wales. Steve says false wireworms have chewed stems just below the ground level, causing patchy germination of crops. Steve estimates that between 5-10% of wheat plants are completely missing across several paddocks at 2-3 leaf stage.

It appears the species responsible for these attacks is the eastern false wireworm (Pterohelaeus spp.). This species is a sporadic pest of cereal crops in eastern Australia. Eastern false wireworm larvae are typically large and range in colour from cream-tan to yellow-orange. They have a hardened cylindrical body with a darker ring around each segment, giving the appearance of bands. Larvae have 6 legs, a rounded head and reach 50 mm in length. Adult beetles are dull black in colour and approximately 25 mm long. They are sometimes referred to as ‘pie-dish beetles’ due to their body shape and the broad flanges (rims) around the edges of their body.

Eastern false wireworms can often be found in paddocks but cause little (if any) damage to cereal crops. The larvae typically attack germinating crops if the soil is dry and there is insufficient organic matter to feed on. False wireworms mostly attack crops from May-July, but can also cause damage later in the season. We have previously received reports of damage occurring as late as August and early September.  Thus, it is important to continue to check paddocks by digging to a depth that includes the moist soil layer where larvae will be present. Repeat this process a number of times across the paddock to get a representative sample. Paddocks coming out of long-term pasture are at most risk.

Chlorpyrifos is registered as a foliar spray against false wireworms in certain broadacre crops, and is reported to provide reasonably good control. In paddocks with a history of false wireworm problems, growers should consider cultural controls. Removal of trash is an effective strategy, while cultivation before seeding may reduce the survival rate of larvae. Consider sowing a pulse crop if high populations of eastern false wireworms are known to be present.

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