Author
Zane W McGrath
mcgrathz@landcareresearch.co.nz
Bioeconomy Science Institute – Manaaki Whenua – Landcare Research Group
Auckland
Coauthors
Quentin Paynter, Bioeconomy Science Institute – Manaaki Whenua – Landcare Research Group
Stephanie Morton, Bioeconomy Science Institute – Manaaki Whenua – Landcare Research Group
Abstract
Chinese privet (Ligustrum sinense) is a small tree, native to East Asia that is now invasive in many countries around the world including New Zealand. A tingid bug Leptoypha hospita, was introduced to New Zealand as a biological control agent for L. sinense in 2015. It established readily and extensive leaf chlorosis was observed on L. sinense saplings growing at a release site in Auckland just a few months after L. hospita was released. However, L. hospita failed to live up to its early promise and population densities are now generally low, causing minor damage with no apparent impact on L. sinense populations. It was hypothesised that L. hospita failed to reach high population densities due to predation. A survey conducted at L. hospita release sites around Auckland identified several arthropod predators commonly in association with L. hospita including the larvae of an invasive green lacewing Mallada basalis. Due to the timing of the arrival of M. basalis in mainland New Zealand (first recorded in 2017), and its ability to feed on L. hospita it was a prime candidate for explaining the failure of L. hospita despite its initial promise. We therefore investigated the impacts of M. basalis feeding on L. hospita populations and the tritrophic interactions between the host plant L. sinense, the herbivore L. hospita, and predator M. basalis in a shade house setting. This confirmed that M. basalis predation can significantly reduce the impact of L. hospita on L. sinense.
Keywords
Predation
Leptoypha hospita
Ligustrum sinense
Mallada basalis
tritrophic interactions
Highlights
L. hospita failed to live up to early promise
Tritrophic interactions can help explain biocontrol agent effectiveness
M. basalis predation can significantly reduce the impact of L. hospita on L. sinense.