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NEW ZEALAND BEEKEEPER, DECEMBER 2016
SPHECOPHAGA VESPARUM: ESTABLISHMENT AND RECOVERY RATES PEST AND DISEASE CONTROL
B.J. Donovan, Donovan Scientific Insect Research, Canterbury Agriculture and Science Centre, Lincoln E-mail: Barry.Donovan@Plantandfood.co.nz
I was the scientist in the Entomology Division of the old DSIR who instigated and managed the wasp biocontrol project from 1979 to mid-1992, and thereafter operating privately until the Foundation for Research, Science and Technology terminated my funding in 2005.
At Pelorus Bridge, 1,034 developing wasps had been killed in one nest. The nest was poisoned on 16 May 1988 when still very active, so if the colony had been left to die naturally some weeks later, the number of wasps killed would have been even greater. This nest was 625 m away from the nearest parasitoid release box, so parasitoids flew at least that distance to attack the nest. Barlow, Beggs and Moller (1998) believed that the parasitoid was increasing its population about three-fold annually, and in subsequent years was spreading at a mean rate of 1 to 1.5 km per year, and by 1993 up to 22,950 nests would have been parasitized. Now, after 28 years, nests up to 42 km away could be being attacked. But at Pelorus Bridge one attacked nest was found 7.1 km from the parasitoid release site in the third year after the first parasitoid release (J. Beggs pers. comm.), which means that parasitoids had dispersed at a mean annual rate of 2.36 km per year. At this rate, after 28 years parasitoids could by now be up to 66 km away. So because established parasitoids could have been dispersing widely from a release site, we cannot be at all sure as to how many separate establishment events there may have been. However, the large distances between some of the earlier recoveries suggest that there were probably at least half a dozen separate establishment events in the Canterbury area alone. This further suggests that over the country there were probably a great many. If so, an extrapolation from the data of Barlow, Beggs and Moller (1998) indicates that many millions of wasps have been and are being killed annually. Far from“failing so miserably”, the wasp parasitoid has been and is being very successful.
Groenteman (2016) says the imported wasp parasitoid Sphecophaga vesparum vesparum which our team released widely over the country is established at only two sites, and so has “failed so miserably”. The facts are that following the first release of parasitoids at Pelorus Bridge in Marlborough in 1987, the parasitoid was found to have attacked two nests of the common wasp Vespula vulgaris by 1988. Later the parasitoid was recovered from a German wasp nest, V. germanica , in east Christchurch, and from a common wasp nest in the Botanic Gardens in central Christchurch. Subsequently attacked nests have been found in 12 sites ranging from Ashley Forest and Mount Grey (30 km and 40 km north of Christchurch, respectively), and 10 other sites in the hilly areas to the west and northwest of Christchurch from View Hill near the Waimakariri River about 50 km from Christchurch, to near Hawarden about 65 km away in a straight line in North Canterbury. These later recoveries were made mainly by Mr Geoff Watts, with the most recent being the View Hill discovery in mid-April this year. Most of the sites are from 10–20 km apart. During summer 1990, a staff member of the Tararua District Council reported the discovery of eight parasitoid cocoons in a piece of comb 10-cm square from a nest of the German wasp in the Tararuas. The attacked nest was about 800 m from a parasitoid release box. On 12 May 2014, comb from a common wasp nest collected at Wainui on the western shore of Akaroa Harbour, Banks Peninsula, was placed into a sealed container at the Canterbury Agriculture and Science Centre at Lincoln. Seven days later, an adult parasitoid
emerged from the comb, with another on the eighth day. Previous studies of the life cycle of the parasitoid showed that at least nine days elapsed from the laying of eggs to the first emergence of adults, so the appearance of an adult on the seventh day suggests that the nest was attacked in the field. From another common wasp nest collected and handled similarly, parasitoids emerged eight days after it was collected in Akaroa. Comb of the common wasp collected by Geoff Watts from Mt. Thomas, Canterbury, March 1998. One hundred and thirty cells contain cocoons of the parasitoid Sphecophaga vesparum vesparum , most of which appear orange. For each cocoon, one developing wasp has been killed.
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