by Melissa J Luther

Created on: April 18, 2010   Last Updated: June 04, 2010

The Hadda Beetle and New Zealand agriculture: Serious threat or minor nuisance?

In January 2010, Hadda Beetles were discovered in Dove-Myer Robinson Park in Auckland. While the number of bugs found was small, they feed on important crops, so officials and farmers were concerned about how this discovery would affect New Zealand agriculture.

The Ministry of Agriculture immediately began a controlled spraying programme as well as a surveillance programme to determine just how widespread the threat might be. On 25 March, MAF biosecurity New Zealand (MAFBNZ) announced that the Hadda Beetle is established throughout central Auckland and eradication is not an option.

> What is the Hadda Beetle <

The Hadda Beetle is a common beetle found throughout much of Australia, Asia and some Pacific Islands. The adult beetle is similar to a ladybird in appearance, with a yellow/orange body and black spots, numbering about 26-28. Two distinctive spots at the midline of the back are often more square-shaped than round. Adult Hadda Beetles can fly up to 500 metres.

Hadda Beetle larvae are about 7 cm long, pale yellow in color and covered with spiny black hairs. Adult beetles are also 7-10 mm in size. Both larvae and adults feed on the same plants, scraping away the leaf surface and leaving behind a characteristic lacy appearance.

Hadda Beetles feed mostly on plants in the solanaceace family. This family includes crop plants like potato, tomato and eggplant.

> How Serious is the Hadda Beetle Threat <

In its March announcement the MAFBNZ estimated that the Hadda Beetle may have invaded New Zealand in 2006, based on the maturity of the beetles found. So far, it has been found feeding only on the weed Solanum nigrum, black nightshade. The fact that neither potato nor tomato crops appear to have been affected yet suggests that the threat may not be as serious as originally feared.

This is potentially good news since the effectiveness of treatment is not known. MAFBNZ estimates that eradication, if it is even possible, could take four years and cost as much as $200 million. Considering that the beetle may have been in the country for as much as four years without targeting crops, or even being detected, this cost cannot be easily justified.

Of course, the fact that the Hadda Beetle has not yet invaded crop fields does not mean vigilance is not justified. The possibility that the beetle could move on from black nightshade to crop plants cannot be discounted. However, since the invasion has been detected before the beetle has targeted crops, officials and farmers have a chance to create a management plan for this pest without being in crisis mode. New Zealand already has a strong response and management system for unwanted pests and this should help the country minimize any impact from the unwanted Hadda Beetle.

Learn more about this author, Melissa J Luther.
Click here to send this author comments or questions.