Revisiting interactions between Jumping plantlice and eucalypts using a high-tech, experimental approach

A project undertaken at the Department of Zoology, La Trobe University, and supervised by Martin Steinbauer

Jumping plantlice (or 'psyllids') are tiny sap-sucking insects closely related to cicadas. The Australian psyllid fauna comprises 364 species belonging to 58 genera (Hollis, 2004). While the winged adult psyllids are rarely seen (Fig. 1), the shelters (or ‘lerps’) of the juvenile stages are familiar to most Australians as the white, yellow or black shell-like structures on the leaves of eucalypts (Fig. 2). Chronic outbreaks of psyllids are primary causes of eucalypt ‘dieback’ (also called ‘rural tree decline’; Reid & Landsberg, 2000). Psyllid feeding causes local leaf necrosis thereby reducing photosynthetic efficiency and hastening leaf abscission (Fig. 2). On the flip-side, however, the excreta of nymphs, their lerps and the insects themselves represent an important food source for a vast array of animals, including birds, some mammals and many other insects, especially ants (Fig. 3).

Psyllid outbreaks have been studied by a number of Australian researchers in the past with leaf age/quality and host plant stress suggested as initiating eruptions (e.g. Clark, 1963; White, 1969). Surprisingly though, experimental studies of psyllid responses to leaf traits purported to drive eruptions have rarely been conducted in Australia (see Taylor, 1997; Stone et al., 2010).

To better understand and perhaps even predict outbreaks, psyllid responses to a range of leaf and plant conditions needs to be revisited using the latest insect-plant interactions research methodologies, e.g. olfactometer bioassays and measurement of chlorophyll concentration and fluorescence. This project will:

1. Quantify the influences of leaf age and toughness  on the survival of Cardiaspina, Glycaspis and Creiis nymphs,
2. Quantify attraction and repellence responses of adult psyllids to host plant odours &
3. Quantify responses of nymphs and adults to exposure to host plants of variable photosynthetic efficiency (a physiological indicator of plant stress).

References

Clark LR (1963) Factors affecting the attractiveness of foliage for oviposition by Cardiaspina albitextura (Psyllidae). Australian Journal of Zoology 11: 20-34.

Hollis D (2004) Australian Psylloidea: jumping plantlice and lerp insects. Australian Biological Resources Study, Canberra.

Reid N & Landsberg J (2000) Tree decline in agricultural landscapes: what we stand to lose. In: Hobbs RJ & Yates CJ (Eds.) Temperate Eucalypt Woodlands in Australia: Biology, Conservation, Management and Restoration, pp. 127-166. Surrey Beatty & Sons, Chipping Norton.

Stone C, Chesnut K, Penman T & Nichols D (2010) Waterlogging increases the infestation level of the pest psyllid Creiis lituratus on Eucalyptus dunnii. Australian Forestry 73: 98-105.

Taylor GS (1997) Effect of plant compounds on the population dynamics of the lerp insect, Cardiaspina albitextura Taylor (Psylloidea: Spondyliaspididae) on eucalypts. In Ecology and Evolution of Plant-Feeding Insects in Natural and Man-Made Environments (Ed. A Raman) pp. 37-57. New Delhi; International Scientific Publications.

White TCR (1969) An index to measure weather-induced stress of trees associated with outbreaks of psyllids in Australia. Ecology 50: 905-909.