Biocontrol introduction
Target pest: Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), greenhouse whitefly
Agent introduced: Encarsia formosa (Hymenoptera: Aphelinidae)
Imported:
1931, 1932, 1933
Import source:
England
Import notes:
Cameron et al. (1989) - there were four attempts to import and establish E. formosa from the Institute of Entomology, England. Three boxes of E. formosa sent in cool storage were received in January 1931, but no parasitoids emerged. A second consignment on living plants in boxes arrived in January 1932 but this also failed. A third consignment, sent in cool storage via Panama, arrived in January 1933; 20 E. formosa adults emerged but they failed to establish in a greenhouse at Palmerston North. Later in 1933 a fourth shipment was received and a small colony was established in a greenhouse, reared through the winter and a small quantity distributed for release in spring. In 1934-35 small quantities distributed for release. Rearing continued in 1935-36 and it was distributed on request. In 1973, the Department of Agriculture established a colony of E. formosa at Levin in the lower North Island, from parasitoids collected in Auckland (and supplemented with parasitoids collected in Christchurch in 1976 and 1977). The colony was maintained until 1980 to supply growers. Since 1980, a colony to supply growers has been established at the Department of Scientific and Industrial Research in Auckland with parasitoids from Christchurch greenhouses originally supplied from the Levin colony.
Released:
1933
Release details:
Cameron et al. (1989) - in 1933, a small quantity of E. formosa were distributed to tomato growers in late-spring. In 1934-35 small quantities were supplied to greenhouse growers and in 1935-36 the parasitoid was distributed on request. In 1972-73, E. formosa was sent from Auckland, North Island to Christchurch, Canterbury, South Island to control T. vaporariorum in several greenhouse crops. Growers have since been supplied with E. formosa for inundative releases in greenhouses from the Levin colony (1973-80) and the Auckland colony (1980-present) [see Cameron et al. (1989) entry in ‘Import notes’ section]. Commercial production of E. formosa is planned.
Establishment:
Cameron et al. (1989) - it appears that until programmes started in the 1970s that relied on multiple releases of E. formosa into each crop, growers were supplied for several years and that after this they relied on the parasitoid to appear naturally in greenhouses from populations surviving outside. From the 1934-35 releases, E. formosa overwintered in Hawke’s Bay in the North Island and spread north to greenhouses and fields around Hastings. During the 1950s and 1960s T. vaporariorum was mainly controlled with new pesticides; during this period E. formosa appears to have survived outdoors. It was reported in 1963 that it was established in the North Island and in Nelson in the South Island.
Impacts on target:
Cameron et al. (1989) - since becoming established in Hawke’s Bay following the releases in the 1930s, there have been several reports of E. formosa controlling T. vaporariorum in certain situations. In 1976 it was reported that the parasitoid did little to control outside populations of whitefly until rather later in the season, and that T. vaporariorum was more numerous in the 1970s and E. formosa less common. Since the early-1970s, inundative releases of E. formosa have been used to control T. vaporariorum in some greenhouse crops in New Zealand, and since 1981, integrated pest management (IPM) systems have been developed for several greenhouse crops in this country.
Cameron et al. (1993) - Encarsia formosa is categorised as exerting “substantial” control (defined as “other control measures are only occasionally required”) over T. vaporariorum. The value of the establishment and inundative release of E. formosa depends on the particular crop and integrated pest management (IPM) programme being considered.
References
Cameron PJ, Hill RL, Bain J, Thomas WP (1989). A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1874-1987. Technical Communication No 10. CAB International Institute of Biological Control. DSIR Entomology Division. 424p.
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
