Biology and ecology of Essigella californica (Essig) on Pinus radiata D.Don. in Australia
Date
2005
Authors
Wharton, Trudi
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The Monterey Pine aphid Essigella californica Essig is native to western North America. In Australia, E. californica is an introduced 'pest' that has the potential to cause economic loss to the Australian softwood forestry industry. This study is the first detailed examination of E. californica 's life history attributes. Laboratory cultures of E. californica were also the first successfully established and maintained. The rate of development, survival and reproduction, and life table parameters of E. californica were determined at 10°C, l5°C, 20°C and 25°C, which allowed predictions of how populations of E. californica in commercial pine plantations would respond to changes in temperature. Unlike the majority of aphid species that develop through four instars, the apterous morph of E. californica was found to develop through only three instars. This difference in instar number was also validated by an analysis of field-collected samples. The adaptive significance of this finding was discussed in relation to other aspects of this species' life history.
An 18 month-field study of three populations found that E. californica is able to survive year round in commercial Pinus radiata plantations in the ACT. Although E. californica population showed seasonal fluctuations, the effect of temperature alone in the field was unable to fully explain the massive increase in population numbers seen in the autumn and winter of 2001. This suggests that population changes are therefore the result of the interaction of a number of biotic and abiotic factors.
Essigella californica has a significant preference for yellow P. radiata needles over green needles, which is likely to influence the distribution of E. californica on hosts within plantations. Scanning electron microscopy revealed that E. californic probed via the stomata on P. radiata needles, and EPG monitoring provided an insight into feeding behaviour.
Two CLIMEX models were developed to predict the Australian and global distribution of E. californica under current climate conditions based upon the aphid's known North American distribution. The climate in regions where commercial pine plantations are generally established in Australia were found to be very compatible with the requirements for E. californica survival, development and reproduction. Essigella californica is well suited to the Australian environment where its host P. radiata is grown in extensive monocultures, the climate is generally favourable for growth, survival and reproduction, and specialist natural enemies are absent. A range of factors act to regulate E. californica populations so that the species will be more of a 'pest' in some years than others.
Description
Keywords
Citation
Collections
Source
Type
Thesis (PhD)
Book Title
Entity type
Access Statement
License Rights
Restricted until
Downloads
File
Description
Thesis