Essigella californica in Australia
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Formerly known as the Forest Research Institute, Scion has been a leader in research relating to forest health for over 50 years. The Rotorua-based Crown Research Institute continues to provide science that will protect all forests from damage caused by insect pests, pathogens and weeds. The information presented below arises from these research activities.
From Forest Health News 105, March 2001.
The Monterey pine aphid, E. californica, was first found in New Zealand in 1998, and population trends are being monitored in selected pine plantations over a two-year period (Forest Health News, Nos. 72, 73, 82, 99). The aphid is also present in Australian pine forests where it occurs in southern Queensland, New South Wales, Victoria, South Australia, Tasmania and Western Australia. Until recently it was considered to be a threat to Australian Pinus radiata plantations. However, over the last spring and summer period, Australian researchers have recorded very low population levels in most localities.
The only research currently being conducted on E. californica in Australia is that by Trudi Wharton, a PhD student at the Australian National University. Her work indicates that E. californica reproduces parthenogenetically, since no sexual stages have so far been found. Under favorable conditions the generation time is approximately a week, so like all aphids it has the potential to build up rapidly into large populations. However, numbers may be kept in check by competition with other aphid species. In New Zealand Eulachnus brevipilosus is frequently found on Pinus radiata foliage later in summer, and competition with this aphid may help explain why large populations of E. californica have not been seen here. However, this remains to be proved.
Despite the dramatic decrease in the current pest status of E. californica , the Commonwealth Scientific and Industrial Research Organization (CSIRO) is continuing with its proposal to gain approval for the importation of biocontrol agents, in case they may still be required if populations increase.
(Clive Appleton, Forest Research)
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