African Black Beetles

Another soil pest chewing at seedling cereals

African black beetle adult (Source: Ken Walker ccv3.0, Museum Victoria)

 

Where have they been reported?

Cereal seedlings in south-eastern NSW have come under attack by African black beetle (Heteronychus arator) since at least mid May. Cereal crops in the Corryong and Holbrook areas of the NSW South West Slopes have been severely damaged in patches, where leaves or complete tillers have been damaged through chewing below the ground. Many adult beetles were successfully controlled with insecticides, although some damage persisted. Crop loss has also been recorded in cereals near Howlong (NSW Riverina).

About the pest

The African black beetle is a soil dwelling insect that favours pastures, particularly newly sown ryegrass and also summer-dormant perennial grasses. Populations of beetles are known to be most prominent in higher rainfall areas where there has been an abundance of summer grasses. However, adult beetles can also fly into paddocks in late summer from nearby breeding areas dominated by perennial grasses.

Adults chew plants at or just beneath ground level, leaving frayed parts. Ryegrass seedlings and grasses may have roots damaged by large populations of adults and larvae. Adults either chew right through the stem or ‘ring bark’ bigger plants.

For more comprehensive information on the African black beetle, including their occurrence, lifecycle, behaviour, damage symptoms and management strategies, go to African black beetle within the new PestNote series.

Our advice

As with most other soil-dwelling pests, the African black beetle is difficult to control and insecticide sprays are often ineffective. Increasing seeding rates is a useful option in paddocks where the pest is anticipated to cause damage. If chemical control is required, spraying just prior to rain or late in the day may be better as beetles often come to the surface at night. Seed treatments may be initially effective.

 

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Source of field reports of African black beetle

Peter Emerson - Agronomist, Elders (NSW Riverina)

Cassandra Skefe – Extension Officer, Riverine Plains Inc. (NSW Riverina)