Biocontrol introduction
Target pest: Phylacteophaga froggatti (Hymenoptera: Pergidae), Eucalyptus sawfly
Agent introduced: Bracon phylacteophagus (Hymenoptera: Braconidae)
Imported:
1986, 1987, 1988
Import source:
Australia
Import notes:
Faulds (1990) - consignments of Bracon (488 females and 552 males) were sent to New Zealand in December 1986 and January 1987 from Melbourne, Australia. More than 600 adult progeny were reared, but this attempt was abandoned when it became obvious that no mating had occurred, resulting in only male progeny. Three further consignments were imported in December 1987 and January 1988; except for a few field-collected females, these parasites were collected as cocoons in Australia and imported mostly as adults. Although only one species of Bracon had been recorded as a parasite of P. froggatti in Australia, it was discovered two distinct species of Bracon with different mating requirements had been imported; these were subsequently described, in 1989, as Bracon phylacteophagus and B. confusus. Bracon confusus made up only approximately 2.5% of the imports in both 1986-87 and 1987-88. Rearing of B. confusus was discontinued in order to concentrate on B. phylacteophagus, the principal parasite of P. froggatti, and a simple procedure to breed and rear B. phylacteophagus was quickly identified.
Released:
1988
Release details:
Faulds (1990) - all releases of B. phylacteophagus were of F1 or later generation individuals reared in the laboratory in New Zealand. Between 19 February and 19 July 1988, 13 releases were made at Maungatapu and Te Maunga (Bay of Plenty, North Island), with a total of 58 females and over 1,400 males released. The five females released at Maungatapu on 25 February could have been B. confusus as it was subsequently discovered that most female emergences in the laboratory between the previous release date (22 February) and 25 February were B. confusus [see Faulds (1990) entry in 'Import notes' section]. The mid-winter releases probably had little chance of establishment. Between 11 January and 6 April 1989, 22 releases were made in the North Island at 12 localities in the Bay of Plenty, Waikato, Coromandel, Auckland and Northland regions, and one release near Hastings (Hawke's Bay) where there is a localised population of P. froggatti, with a total of 950 females and approximately 9,600 males released.
Faulds (1991) - between December 1989 and February 1991 a total of 4,939 adult males and 1,835 adult females, and several hundred cocoons, were released at 25 North Island locations in the Northland, Auckland, Coromandel, Waikato and Bay of Plenty regions, and at Hastings (Hawke’s Bay) and Palmerston North (Manawatu) where there are localised populations of P. froggatti.
Establishment:
Faulds (1990) - the first recovery from Maungatapu was on 19 March 1988 when a sawfly mine containing a female B. phylacteophagus larva was found, proving that the parasites released in February had mated in the field (unmated females produce male offspring). Further cocoons and adults were seen regularly at this site during 1988 until 9 August, and a fresh cocoon collected on 5 January 1989 indicated that the parasite had successfully overwintered. At the end of January 1989, 29 of 30 sawfly mines examined at Maungatapu had parasites present and parasite cocoons were found 2 km away from the release site. A survey for B. phylacteophagus in the Tauranga district (where Maungatapu is located) on 3 May detected its presence throughout the area to 5 km to the west and 1 km to the east from the release site. Bracon phylacteophagus has been recovered from six localities in Bay of Plenty and Waikato, with females recovered at four of the localities, indicating probable establishment.
Faulds (1991) - the spread of B. phylacteophagus has been spectacular. By July 1991 it was established in most areas north of a line from Houpoto-Murupara-Bennydale-Piopio (Waikato and Bay of Plenty) (the southern boundary of the main sawfly infestation) to Auckland, spreading at up to 40 km per year from monitored release sites. North of Auckland, B. phylacteophagus has been recovered up to 50 km from release sites but, as many areas have not been inspected, distribution records are incomplete. South of the southern boundary of the main sawfly infestation, B. phylacteophagus has been recovered in Hastings and Palmerston North up to 10 km and 14 km respectively from release sites, and was found in Gisborne in February 1991, approximately 150 km from the nearest release site. The presence in Gisborne is most likely the result of immature stages taken into the area on sawfly-infested plants. Further spread from areas where B. phylacteophagus is now well established, and also from the more recent release sites, should ensure that the population will be practically continuous throughout the sawfly-infested area by May 1992.
Impacts on target:
Faulds (1990) - the release site at Maungatapu had been chosen in 1988 because of an extremely heavy sawfly infestation on the trees that year. In comparison, by mid-March 1989, only a few sawfly mines were present and, except for the very small mines, all contained a parasite. Considering that the establishment of B. phylacteophagus at Maungatapu-Tauranga was from as few as 17 females plus males, spread has been spectacular. The high percentage of sawfly parasitized (up to 98%) is also very encouraging. If the results from the 1988 Maungatapu releases are indicative of what will happen at the 1989 release sites, B. phylacteophagus should be widespread and may dramatically reduce the sawfly population by late-summer 1990.
Faulds (1991) - trees severely damaged by P. froggatti before the establishment of B. phylacteophagus had no or insignificant damage when the parasitoid had been established for more than one season. At two monitored sites, Cambridge (Waikato) and Te Puke (Bay of Plenty), percentage foliage damaged by P. froggatti in February 1989, at the time of parasitoid release, was 79.5% and 40.5%, respectively. In January 1990, 7.5% of foliage was damaged at both sites; in January 1991, 0.0% and 0.5%, respectively. By May 1993, P. froggatti in New Zealand should be a non-pest insect because of effective control by B. phylacteophagus.
Cameron et al. (1993) - Bracon phylacteophagus is categorised as exerting “complete” control (defined as “control of the target over an extensive area so that pest outbreaks are rare or other control treatments are rarely necessary”) over P. froggatti.
General comments:
Faulds (1990) - Phylacteophaga froggatti, an Australian leaf-mining sawfly which infests species of Eucalyptus, was first reported in New Zealand in March 1985 near Auckland International Airport. During the 1985-86 season the sawfly spread rapidly throughout the greater Auckland area and also became established in isolated areas in the northern half of the North Island. By June 1989 it was established in most of the North Island north of Tokoroa and in the Hastings area.
References
Cameron PJ, Hill RL, Bain J, Thomas WP (1993). Analysis of importations for biological control of insect pests and weeds in New Zealand. Biocontrol Science and Technology 3(4): 387-404
Faulds W (1990). Introduction into New Zealand of Bracon phylacteophagus, a biocontrol agent of Phylacteophaga froggatti, eucalyptus leaf-mining sawfly. New Zealand Journal of Forestry Science 20(1): 54-64 https://www.scionresearch.com/__data/assets/pdf_file/0007/59965/NZJFS20154FAULDS.pdf
Faulds W (1991). Spread of Bracon phylacteophagus, a biocontrol agent of Phylacteophaga froggatti, and impact on host. New Zealand Journal of Forestry Science 21(2/3): 185-93 https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.707.5302&rep=rep1&type=pdf
