July 3rd, 2023Natural born stink bug killer

The tiny samurai wasp is a potential pre-emptive biocontrol agent for the serious agricultural pest Brown Marmorated Stink Bug, if it establishes here, research scientists at the CSIRO say.

Ever get that feeling you’ve lost something really important? Is it in your other pocket? Or down the back of the couch? We can’t find the Samurai wasp, which we know was here before. It’s important as a potential future biocontrol superhero against a serious agricultural insect pest threatening Australia.

Samurai were ancient Japanese warriors, often serving in private armies. The CSIRO now says it’s hoping the namesake wasp could go into battle against one of world’s worst biosecurity pests, if it ever establishes here: Brown Marmorated Stink Bug (BMSB).

BMSB is in the top 10 National Priority Plant Pests for Australia. If introduced here, it would cause serious damage to fruit and vegetable crops and ornamental plants. It’s a voracious pest, which feeds on more than 300 plant species including key agricultural crops. And it can grow large populations and become a household nuisance as it seeks shelter indoors over winter.

The tiny Samurai wasp, Trissolcus mitsukurii, is about the size of a sesame seed. It is one of the main egg parasitoids of BMSB in its native range in Japan. It can’t sting humans. And it’s so small it’s easy to miss.

The Samurai wasp was first recorded in Australia in 1914, but it was given a different name. It was also introduced in a biocontrol program in 1962 to help control the Green Vegetable Bug (GVB), Nezara viridula.

Subsequently, it was found in the ACT, NSW, Queensland, Victoria, Western Australia (WA) and South Australia. But it hasn’t been recorded since 1998, when the last specimens were found in ACT and WA.

If the Samurai wasp is still here, and can be found, then it could be a pre-emptive biocontrol agent ready to attack BMSB if it spreads here. A biological control program would involve breeding the wasp up in large numbers and releasing it to target BMSB wherever it is found in any future incursion.

But first, scientists with the CSIRO say, we need to find out more about which hosts T. mitsukurii uses here. Australia has a high number of endemic stink bug species (94 genera and 330 species) so it probably uses some of these as hosts. This large number of native stink bug species would also make it tricky to import new host specific exotic biological control agents.