Greedy new moth set to guzzle gorse

Greedy new moth set to guzzle gorse

Gorse, possibly New Zealand’s worst weed, may be in for a hard time, with the latest biological control agent brought in to attack the pesky shrub now successfully established.

The gorse colonial hard shoot moth (Pempelia genistella) is originally from Portugal and can only survive on gorse, so it poses no threat to native or other desirable plants. Its caterpillars damage gorse plants by feasting on the foliage in autumn, and on buds, shoots and flowers in spring.

Landcare Research biocontrol expert Lynley Hayes says the moth has been found in good numbers at one of the first release sites at Redcliffs, a coastal suburb of Christchurch. There are plans to check other release sites throughout New Zealand in future.

“When we introduce biological control agents there are no guarantees that they will survive in the wild, so the moths’ success in Christchurch is an important milestone for us,” Ms Hayes says.

“The moths are already more abundant at Redcliffs than you would typically find in their native Portugal, probably because their own specialist natural enemies do not occur in New Zealand. We can now start harvesting these moths and distributing them to new sites.”

This newest agent joins three other foliage feeders and two seed feeders that were also brought to New Zealand to assist in the battle against gorse. All are now established and most are still spreading, but are likely to take some years to achieve good coverage.

“In the meantime, we must be very patient and give the agents the best possible chance to go forth and multiply,” Ms Hayes says.

“We hope that eventually our combined biological control attack on gorse will reduce its vigour, and eventually lead to its decline. Modelling predictions suggest that biological control stands a good chance of being successful in the longer term.”

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