South Island debut for parasite wasp

Press, 6 December 1985, Page 3

South Island debut for parasite wasp

By

JOAN BEGG

Wasps, which have been running amuck, stinging and frightening people and damaging fruit crops and beehives, may soon find themselves beaten or rather eaten by insects their own size.

A parasite wasp, which in reality looks nothing like a wasp, has been introduced in New Zealand specifically to reduce its pesky relatives.

The Department of Scientific and Industrial Research branch at Lincoln imported the parasite wasp, Vespula ichneumonidae, from Europe in 1978. The parasite has since been tested for its effectiveness in killing off wasps’ nests and is now almost ready for its South Island debut.

The only thing holding the department back from releasing the insect is money. Although about 2000 parasites have been bred, hundred of thousands would be needed to make sufficient impact on wasps’ nests in the South Island, according to Dr Barry Donovan, an entomologist in the D.S.I.R. at Lincoln.

Essentially the centime-tre-long, slim-bodied, clear-

winged parasite wasp sneaks into other wasps’ nests (in New Zealand the nests of the German and common wasps, Vespula germanica and Vespula vulgaris respectively) and lays its eggs in the brood cells, where ydung wasps are bred. The parasite eggs develop into larvae which then feed on the developing host wa s.P-

The cost of propagating the parasite wasps to a sufficient number and then releasing them is expected to be about $77,000 a year, and so the department has approached territorial councils throughout the South Island offering to release the parasite wasps in thenregion in return for $l5OO a year for two years. Dr Donovan said the councils would effectively provide only half the finance, the rest being paid by the Government. At present local councils spend hundreds of thousands of dollars each year eradicating wasps’ nests, usually with poison. The deal offered by the department, as well as being cheaper in the shortterm, should be far more effective long-term, said Dr

Donovan. However, only those councils which pay for the parasites will get them. Nonpaying local authorities would be unlikely to reap the benefits of their neighbouring paying councils’parasitewasps for many years, he said. Dr Donovan said the department could not offer councils any guaranteed rate of effectiveness but at the least the parasite wasp would have a notiiceably beneficial effect for less cost than councils now paid. It was a biological control problem and the influence of factors such as the parasite being a new species in a new environment, dining on a wasp species that was new to it, could not be accurately predicted. European work had shown, however, that the parasite wasps were capable of destroying other wasps’ nests. The advantages of using such a carnivorous creature to reduce wasps in New Zealand are not offset by any disadvantages, according to Dr Donovan. The parasite wasp has no nasty side-kicks of its own. It attacks only wasps, cannot

sting, and in Europe has been found only in wasps’ nests or the occasional flower on which it might be resting.

Furthermore, although the parasite has a voracious appetite for other wasps, there is no danger that it will eradicate its food supply. Individual nests would be destroyed but the wasps would only be reduced to a level where they were no longer a nuisance, said Dr Donovan.

The department has sent letters about the parasite wasp deal to 70 South Island councils. Of the eight replies so far, one is positive and four are considering the deal. The others thought the programme should be fully paid by the Government, said Dr Donovan.

The distribution of parasite wasps would begin in autumn next year, after the parasite propagation programme was expanded to match incoming funds. Dr Donovan said he hoped to see the wasp problem in the South Island reduced within several years. If successful, the programme would be used in the North Island.