Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Privet Lace Bug Shows Early Promise

Small plant showing lace bug damage.

Small plant showing lace bug damage.

The Environmental Protection Authority (EPA) granted approval to release the privet lace bug (Leptoypha hospita) in May 2015. Waikato Regional Council was the applicant on behalf of the National Biocontrol Collective. This is the first agent to be used against Chinese privet (Ligustrum sinense) both in New Zealand and worldwide.

The lace bug adults and nymphs pierce and suck the sap from the privet leaves, damaging the leaf tips and, if the attack is severe, causing defoliation, all of which reduces the vigour of the plant. The lace bugs have fortunately proven to be relatively easy to rear, which allowed 11 releases to be made last spring/early summer in the Auckland, Bay of Plenty, Waikato and Wellington regions.

Visits this autumn to an Auckland site have generated an early surge of excitement. It is not unusual when releasing weed biocontrol agents to not be able to find any sign of them, or only very subtle indications for the first few years following release. However, at Mt Richmond seedling plants in the shade were clearly showing signs of attack, with much bleaching of the leaves, after only a few months. “This early sign in the field, on top of damage observed to plants in our rearing colony, augers well that the lace bug will establish and be able to cause considerable damage to Chinese privet,” said Quentin Paynter. In its native range (China) the lace bug is reported to attack a range of privet species in addition to Chinese privet. Host-range testing has indicated that other Ligustrum species present in New Zealand, such as the larger tree privet (Ligustrum lucidum) are also potential, but less-preferred hosts.

It is not certain how many generations of the lace bug will be produced per year in New Zealand, but at least two are likely. It is also not certain whether additional agents will be needed to provide sufficient control of weedy privet species in New Zealand. For now it is a matter of wait and see, but the project is off to a good start.

This project is funded by the National Biocontrol Collective.