Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 18 - Chalcidoidea (Insecta: Hymenoptera) - Introduction, and review of smaller families - Biological Control in New Zealand

Noyes, JS; Valentine, EW 1989. Chalcidoidea (Insecta: Hymenoptera) - introduction, and review of smaller families. Fauna of New Zealand 18, 96 pages.
( ISSN 0111-5383 (print), ; no. 18. ISBN 0-477-02545-5 (print) ). Published 02 Aug 1989

Biological Control in New Zealand

Many of the chalcids encountered in modified environments in New Zealand are exotic, and it is probable that a high proportion of these arrived, along with their hosts, in the early days of European settlement, on plants, in animal fodder and other foodstuffs, in seeds, timber, etc. The presence of these parasitoids in the new agricultural and horticultural environments undoubtedly served to limit the populations of potential pest insects. Some pests, however, may not have been accompanied by their natural parasitoids, or these failed to establish, requiring the importation of appropriate parasitoids (or other natural enemies) in order to establish some degree of natural control. About 100 exotic species of chalcid now well established in New Zealand are known to have been purposefully introduced.

The first published record of the deliberate introduction of a chalcid is that of the eulophid Pediobius epigonus (Walker) for the control of hessian fly, Phytophaga destructor (Say) in wheat (Kirk 1894). In the early years of this century, during the period when biological control was being developed, introductions of most natural enemies were of predators, particularly coccinellid beetles, for the control of aphids and various coccoids. As activity expanded, parasitic Hymenoptera (including Chalcidoidea) were also imported for the attempted suppression of some pest insects. Notable among these were Aphelinus mali (Haldeman) (Aphelinidae), a parasitoid of the woolly aphid, Eriosoma lanigerum (Hausman) (Tillyard 1921 - 26); and Anaphes nitens (Girault) (Mymaridae), an egg parasitoid of the eucalyptus weevil, Gonipterus scutellatus (Gyllenhal) (Clark 1931).

Successful establishment of such species, and spectacular reductions in pest infestations, gave further impetus to applied biological control as a practical method of insect pest suppression. Various Chalcidoidea were imported subsequently to meet particular problems, with varying degrees of success in establishment and control. The introduction of Habrolepis dalmanni Westwood (Gourlay 1935) (Encyrtidae) resulted in the virtual elimination of golden oak scale, Asterodiaspis variolosum (Ratzeburg), which was threatening to decimate the English oak (Quercus robur) in New Zealand. This scale is now very rarely seen. Achrysocharoides latreillii (Curtis) (=Enaysma splendens of authors) (Eulophidae), in combination with other parasitoids, plays an important part in the control of the oak-leaf miner, Phyllonorycter messaniella (Zeller) (Given 1959, Swan 1973).

A more recent example of outstandingly rapid establishment and spread is offered by Copidosoma floridanum (Ashmead) (Encyrtidae), a polyembryonic parasitoid of green looper caterpillars, Chrysodeixis eriosoma (Doubleday) (Roberts 1979, 1983; as Litomastix sp. and Litomastix maculata). It is now one of the most common chalcids collected in modified, agricultural, and horticultural environments, at least in much of the North Island.

Other introduced chalcids which have become familiar to New Zealand entomologists as valuable biological control agents include Pteromalus puparum Linnaeus (Pteromalidae), a gregarious internal parasitoid of the pupae of the white butterfly, Pieris rapae Linnaeus; Encarsia formosa Gahan (Aphelinidae), attacking larvae and pupae of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood); and Coccophagus gurneyi Compere, a common parasitoid of immature long-tailed mealybugs, Pseudococcus longispinus Targioni Tozzetti.

The foregoing examples are of Chalcidoidea which were purposefully introduced to overcome the lack of natural control of pests, but by far the greater proportion of spccies known to parasitise exotic insects in New Zealand are probably accidental introductions. Thc activities of these species serve to suppress the increase of insects which might otherwise be damaging pests. Few of the exotic parasitoids are known to have adapted to native vegetation, or to native hosts, but some endemic chalcids - e.g., some trichogrammatid parasitoids of the eggs of Tortricidae and Noctuidae - have followed their natural hosts to exotic plants in modified environments. Most of the native species are confined to native forest, scrubland, tussock grassland, and alpine environments where their natural hosts occur. In these situations Chalcidoidea, through their parasitism of phytophagous and xylophagous insects, may play an important role in the natural or biological control of potentially destructive species.

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