Eradication project targets moth reproduction
The breeding cycle of the painted apple moth is about to be disrupted by the release of sterile male painted apple moths
in Auckland from next week, providing another tool in the operation to eradicate the pest.
Ian Gear, painted apple moth project director, said the ability to add this tool, known as the sterile insect technique
(SIT), to complement the range of proven eradication tools already being used – including both aerial and ground
operations – will definitely increase the effectiveness of the overall painted apple moth operation and the likelihood
of its success.
“As with any project that is aiming for total eradication we have to be wary of being over-confident. However
comparative data for December-January on the density of moth finds detected by traps in the painted apple moth zones
shows an undeniable decline – from about 1300 male moths trapped in 2001-02 down to 30 male moths in the same period for
2002-03.
“At a point like this, we have to look to sound science to see how we meet the difficult challenge of moving even closer
towards eradication. Using this technique helps us to ensure that the small percentage of female moths in the painted
apple moth zone, often in inaccessible areas, will be reached by sterile males, resulting in the sterility factor being
transferred to subsequent generations. This, coupled with other tools, will assist in collapsing the residual
populations,” Ian Gear said.
John Charles, a lead scientist with HortResearch’s bioprotection team, said the planned release of sterile moths follows
lengthy research into the application of SIT as a valuable complementary tool in the painted apple moth operation.
Although it is new to New Zealand, SIT has been used in more than 40 countries for several decades against a range of
insect pests, including fruit flies. When the sterile moths mate with female moths, the females produce sterile eggs or
offspring.
Because female painted apple moths are flightless, the research focused solely on males and on a technique that would
have a minimum effect on their mobility. Data from HortResearch has confirmed that full sterility and population
collapse will quickly result from the release of sterile males.
The male moths are reared by HortResearch in Auckland and are rendered sterile by exposure to Cobalt-60 under controlled
conditions at the National Radiation Laboratory in Christchurch. Although they have been irradiated the moths are not
“radioactive”. This is a similar procedure to the one used to sterilise a range of imported food products.