Increased regulation of chemical pesticides and rapid evolution of pesticide resistance have increased calls for sustainable pest management. Biological control offers sustainable pest suppression, partly because evolution of resistance to predators and parasitoids is prevented by several factors (e.g., spatial or temporal refuges from attacks, reciprocal evolution by control agents, and contrasting selection pressures from other enemy species). However, evolution of resistance may become more probable as agricultural intensification reduces the availability of refuges and diversity of enemy species, or if control agents have genetic barriers to evolution. Here we use 21 y of field data from 196 sites across New Zealand to show that parasitism of a key pasture pest (Listronotus bonariensis; Argentine stem weevil) by an introduced parasitoid (Microctonus hyperodae) was initially nationally successful but then declined by 44% (leading to pasture damage of c. 160 million New Zealand dollars per annum). This decline was not attributable to parasitoid numbers released, elevation, or local climatic variables at sample locations. Rather, in all locations the decline began 7 y (14 host generations) following parasitoid introduction, despite releases being staggered across locations in different years. Finally, we demonstrate experimentally that declining parasitism rates occurred in ryegrass Lolium perenne, which is grown nationwide in high-intensity was significantly less than in adjacent plots of a less-common pasture grass (Lolium multiflorum), indicating that resistance to parasitism is host plant–dependent. We conclude that low plant and enemy biodiversity in intensive large-scale agriculture may facilitate the evolution of host resistance by pests and threaten the long-term viability of biological control.

The invertebrate pests most commonly affecting New Zealand’s pastoral‐based production in ‘average’ years cause losses of between $1.7B and $2.3B p.a. of which up to $0.9B occur on sheep and beef farms and $1.4B on dairy farms. The native scarab grass grub is the most costly pest causing losses of $140–380 M on dairy farms and $75–205 M on sheep and beef farms annually. The exotic scarab, black beetle, although only affecting approximately 1 M ha, costs dairy farmers up to $223 M and sheep and beef farmers up to $19 M annually. Porina cause losses up to $84 M and $88 M respectively. Pasture nematodes are estimated to cost up to $274 M p.a. for dairy farmers and $326 M p.a. for sheep and beef farmers. Two exotic pests, Argentine stem weevil (ASW) and clover root weevil (CRW) are causing damage estimated at up to $200 M p.a. and $235 M p.a. respectively in dairy and sheep and beef pastures. While CRW is subject to successful biological control management it still causes considerable losses. Lesser pests also contribute to lost production, particularly as they often coexist with more major pests. However, their economic cost to New Zealand is difficult to calculate due to the variable nature of infestations on both temporal and spatial scales. At farm and paddock level, it is abundantly clear that substantial savings could be made if pest management is achieved. It is equally clear that in many instances the tools to do so are limited but if developed would contribute substantially to farm profitability.

Genetic technologies such as gene editing and gene drive systems have recently emerged as potential tools for pest control. Gene drives, in particular, have been described as potential solutions to the pest problems that beset New Zealand. Here we describe the current state of gene drive technologies and present a series of examples to examine the potential benefits and problems arising from gene drive approaches for pest control in New Zealand. We consider the risks and barriers, both biological and social, that would need to be addressed to deploy such systems against our key pests with particular reference to the unique characteristics of New Zealand’s biota, environment and peoples. Gene drives are a potentially useful technology for the eradication of pests in New Zealand but a great deal of research and understanding, as well as public acceptance, is required before they can be implemented.