Black Beetle – Adult

The Black Beetle (Heteronuchus arator) is generally found in the top half of the north island though it has been reported as far south as Wellington.  Originally it was a native from South Africa although it has now been in both NZ for a long time.  

The adult black beetle is approximately 15mm long and has a shiny, black and sturdy in appearance. As an adult it can be found throughout the year but most predominantly from the months of February through until October. The adults burrow into the soil where they also consume the roots of grasses. The larvae which are larger than the larvae of the grass grub are creamy white in colour with a black head and abdomen.

They live in the top 20mm – 50mm of the soil profile where they eat the roots of susceptible species with the majority of the damage done from October through until March. The damage is obvious after a period of hot, dry conditions when the affected plants struggle to uptake sufficient moisture as a result of their impaired root function.

Without regular irrigation these plants will desiccate and die. For that reason treatment is recommended in October and November prior to the worst of the damage occurring.