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Biology of the Fireblight beetle, Acacicola orphana (Erichson) (Coleoptera: Chrysomelidae), a defoliator of Acacia dealbata (Link.)


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Simmul, TL 2001 , 'Biology of the Fireblight beetle, Acacicola orphana (Erichson) (Coleoptera: Chrysomelidae), a defoliator of Acacia dealbata (Link.)', PhD thesis, University of Tasmania.

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Acacicola orphana (Erichson) is a winter developing insect that severely defoliates its host
trees, Acacia dealbata (Link.) and A. mearnsii (De Wild.). Both adults and larvae feed on green
bark and foliage, resulting in damage which may lead to tree death.
This study investigates the biology and ecology of A. orphana, focussing on its developmental
biology, distribution and host-plant relationships.
At the commencement of this project a basic guide to the different stages of A. orphana was
established. Developmental biology was examined in the laboratory, where development from
eggs to adults was found to require 1266 DD > 4.4 °C. Field development studies suggested a
lower threshold. Consequently, inaccuracies were observed when laboratory information was
used to predict the timing of stages in the field. Management strategies therefore need to be
based on field estimates.
Natural enemies of A. orphana identified were; a tachinid, Lixophaga sp., a braconid
hyperparasitoid, Meteorus sp. and a fungal pathogen, Beauveria bassiana. Fourth instar
mortality attributable to the tachinid was up to 17%. Beauvaria bassiana was recovered from
adults only and caused up to 12% mortality.
Geographical distribution of A. orphana was mapped throughout southeastem Australia. This
information was then used to predict the distribution throughout Australia and globally using
CLIMEX, a climate modelling package. Global mapping predicted populations could survive in
African and Asian countries where some Acacia species (in particular A. mearnsii) are
economically important.
On the Australian mainland, A. orphana was observed predominantly on A. mearnsii, rather
than on A. dealbata, which was its main host in Tasmania. Thus, experiments examining
oviposition, larval development and survival between A. dealbata and A. mearnsii were undertaken. Whilst both species experienced similar levels of defoliation in the field, larval development was 25% faster on A. mearnsii.
Acacia orphana and its interactions with Acacia dealbata were the main focus of this study.
Consumption studies showed final instar A. orphana consumed `0.93 g^-1g^-1day^-1` and the
efficiency of conversion was 40%. Initial hypotheses relating to bark feeding behaviour were
disproved, with findings that green bark feeding does not occur due to a lack of foliage, nor
does it enhance the foliage quality for the next generation of larvae.
Further investigations of host-plant interactions involved assessing first instar larval survival
and defoliation on four different A. dealbata provenances. General differences in nutrition,
colour and fluctuating asymmetry of the trees were also assessed. One provenance experienced
significantly less defoliation. Phenotypic differences showed that low foliar nitrogen, low
moisture and redder-coloured foliage were related to increased defoliation and larval survival. It
was hypothesised that climate and environmental conditions primarily regulate the host-plant
interactions of A. orphana.

Item Type: Thesis - PhD
Authors/Creators:Simmul, TL
Keywords: Fire-blight, Wattles (Plants), Beetles
Copyright Information:

Copyright 2001 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2001. Includes bibliographical references

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