Is Biocontrol an Option for Paper Wasps in New Zealand?
Asian paper wasp attacked by unknown fungus in Auckland.
In New Zealand, we have two species of exotic paper wasps, Polistes humilis which is native to Australia and Polistes chinensis antennalis which is native to Asia. Both species have been in New Zealand for several decades and are now widespread but limited by climatic conditions.
Paper wasps are predatory and attack butterfly and moth larvae as well as compete for nectar resources with other insects and birds. They reach high densities (>200 nests per hectare) in places like the far north of New Zealand where conditions are optimal. Paper wasps are also a significant nuisance to animals and humans, giving painful stings.
Options for controlling paper wasps are limited because unlike Vespula wasps (German and common wasps), paper wasps are not attracted to protein baits. Trapping individual workers does not have a major impact on numbers, although manually destroying nests can be successful on a small scale. So, recently, Quentin Paynter and Darren Ward have investigated the potential for biological control of these pests.
Biocontrol of paper wasps has not been attempted anywhere in the world to date. Biocontrol against Vespula wasps has been attempted here using parasites (Sphecophaga spp.) but has unfortunately failed to make much of a dent in wasp numbers. This is thought to be at least in part due to the fact that the Vespula wasps vigorously defend their nests against unwanted intruders. “However, there are reasons to be more optimistic regarding the potential for biocontrol of Polistes wasps,” explained Quentin. The lack of a nest envelope on Polistes nests makes their nests harder to defend. Also while the incidence and impacts of parasitism and disease on Asian and Australian paper wasps are not well known there is, for example, good data from other paper wasps that they are attacked by a wide range of parasitoids, including scavenger moths that exert a major influence on colony longevity. Once nests are bored by such moths, they lose structural strength and cannot be used for long. Furthermore, it has been noted that unlike Vespula spp., Polistes wasps do not have meconium-extracting behaviour (removal of larval waste) which could explain why their nests appear to be more attractive to these scavenger moths.
There are two options for advancing a biocontrol programme for paper wasps in New Zealand. The fi rst would involve conducting surveys in the native ranges of the two species to identify their natural enemies and any prospective biocontrol agents. The second, cheaper approach would be to consider the natural enemies already known to have a major impact on other Polistes species and whether they might be suitable for New Zealand. The advantage of using less specific agents is that any new species of paper wasps that manage to invade New Zealand in the future might also be suppressed early on. Fortunately, because our native hymenoptera are not closely related to the introduced paper wasps, it is unlikely that any potential biocontrol agents would pose a threat to them.
There are many reports of paper wasps predating on monarch butterflies (Danaus plexippus), and native moths and butterflies such as the kawakawa looper (Cleora scriptaria) and kowhai moth (Uresiphita polygonalis aorialis). However, paper wasps do benefit gardeners to some extent by helping to control pests such as the cabbage white butterfly (Pieris rapae). The importance of this to organic gardeners needs to be assessed, especially since biocontrol agents have been established in New Zealand to specifically target these butterflies.
“Overall our review suggests that biocontrol for paper wasps appears quite promising,” concluded Quent. Further research will be undertaken as funds permit.
This project was funded by the Ministry of Science and Innovation through Landcare Research’s Capability Fund.