Approvals to release biocontrol agents

Vespula species wasp application

An application has been submitted to introduce two biological control agents for the German wasp, Vespula germanica and the common wasp, V. vulgaris. Volucella inanis is a species of hoverfly that lays its eggs inside the nests of Vespula wasps and the larvae feed on wasp grubs. Metoecus paradoxus is a beetle whose larvae parasitise wasp grubs. German and common wasps are a major threat to the native biodiversity of New Zealand, and we expect these proposed biocontrol agents to negatively impact wasp numbers.

Background

This application has been submitted by the Tasman District Council on behalf of the Vespula Biocontrol Action Group. Manaaki Whenua – Landcare Research are providing the science, preparing the application and managing the application process, including consultation with EPA, Māori and other stakeholders.

The German wasp, Vespula germanica, and common wasp, V. vulgaris, are eusocial wasps that can form very large colonies of several thousand individuals. Both species typically nest in holes in the ground, but nests are also found in rotten logs or stumps, in forest litter and in trees. In urban areas they nest in hollow walls, attics or aerial locations, for example under the eaves or hanging from rafters. Colonies of Vespula spp. have a caste system, with queens, workers and males (drones). The workers are responsible for collecting food, water and nesting material, caring for the brood and for nest defence. German wasp nests are grey and are constructed with fibres from structurally sound wood whereas nests of the common wasp are brown in colour, made from the pulp of rotting wood. German wasps have the capacity to maintain large overwintering nests whereas the common wasp colonies die in winter.

The German wasp is native to Europe and north Africa and was first confirmed as established in New Zealand at Te Rapa, Hamilton in 1945 (Thomas 1960). Recent phylogenetic research indicated that there have been at least two incursions of this species to New Zealand, with the largest population originating from the United Kingdom and a very small population originating from central Europe (Brenton-Rule et al 2018). The common wasp is native to Europe and parts of Asia (e.g. Pakistan and northern China). Queens of this species were first collected in Wellington in 1978 and nests were later found there in 1982 (Donovan 1984). A phylogenetic analysis indicated at least six incursions of the common wasp to New Zealand, originating from locations in the United Kingdom, Ireland, and Western Europe (Lester et al 2014). Following their introduction, both wasp species rapidly expanded their ranges and are now found throughout New Zealand, including Stewart Island (Clapperton et al. 1989b).

Beech forests at the top of the South Island have the highest densities of wasps in the world. Vespula wasps are generalist predators that attack a wide variety of arthropods including honeybees, butterflies, flies and spiders, but they will also scavenge for protein from animal carcasses and dustbins. They have detrimental effects on normal ecosystem functioning, food webs and the behaviour of native birds. The predation rate of wasps on native invertebrates is believed to be so high that some species are at risk of extinction (Toft and Rees, 1998). Wasps also have a significant impact on New Zealand’s beekeeping industry, being one of the leading causes of colony losses ranging from 9.7% in 2017 to 12.1% in 2018. The damage is regularly ranked as the 3^rd - 4^th highest cause of colony loss (NZ Colony Loss Survey). Vespula wasps are intensely disliked by the New Zealand public through disrupting the enjoyment of the outdoors and recreational activities and the risk of stings, in severe cases leading to hospitalisation or even death. Both the German and common wasp are very destructive invasive pests that cost New Zealand up to $130,000,000 annually in damages and management (MacIntyre and Hellstrom, 2015).

More information about common and German wasps and their control:

• Feasibility study for biocontrol of Vespula

Identification and assessment of risks, costs and benefits

The potential risks, costs and benefits associated with the proposed introduction of Volucella inanis and Metoecus paradoxus to New Zealand, and the expected reduction in the abundance of Vespula wasps have been identified by literature review and by consultation with stakeholders.

• Risks, costs and benefits of Vespula biocontrol

The application will address in detail the significant adverse and beneficial effects identified. The potential benefits of biological control will be the mitigation of the adverse effects of Vespula wasps. The key potential adverse effects relate to impacts of the biological control agents on native flora and fauna. These will be addressed fully in the application:

• the risk of direct damage to native insects
• indirect effects on flora and fauna as a result of disruption of ecological relationships

Volucella inanis female rests near a Vespula vulgaris nest entrance in Egham, England.

The wasp nest beetle, Metoecus paradoxus is a medium-sized beetle (8 – 12 mm) that parasitizes the brood of Vespula wasps. First instar larvae of M. paradoxus enter wasp nests after attaching themselves to the bodies of foraging Vespula wasps, and once inside, the larvae locate and consume one Vespula wasp grub each. Feeding continues until they are ready to pupate and they emerge as adults around the same time as their host would have completed its life cycle.

Volucella inanis also parasitizes the brood of Vespula species, but each larva attacks more than one wasp grub. The first instar V. inanis larva squeezes its way to the bottom of the brood cell of a large wasp grub and begins feeding on the posterior end of the grub. This severely compromises the wasp grub’s vitality. Second instar V. inanis larvae then seek a second wasp grub in the pre-pupal stage. Once the V. inanis larva locates an appropriate wasp grub, it makes its way to the bottom of the brood cell and waits for the wasp grub to close the cell with silk. Once the cell is sealed, the V. inanis larva feeds until it is ready to pupate, effectively killing the wasp grub.