IngentaConnect Role of foliar chemistry versus leaf-tip morphology in egg-batch ...

Authors: Howlett, Bradley G¹; Clarke, Anthony R²

Source: Australian Journal of Entomology, Volume 42, Number 2, April 2003 , pp. 144-148(5)

Abstract:

The Tasmanian eucalyptus leaf beetle, Chrysophtharta bimaculata (Olivier) (Chrysomelidae: Paropsini), deposits batches of eggs on the leaf surfaces of its Eucalyptus hosts. Using a primary host of the beetle, Eucalyptus regnans, the aim of the present study was to examine whether oviposition site discrimination was occurring at the level of the individual leaf and what, if any, chemical attributes were involved in site selection. From field surveys, it was found that 55−65% of egg batches were laid in the leaf-tip zone, despite this zone representing only 5.6% of the total leaf-surface area. Chemical analyses of expanding leaves showed that the concentrations of three essential oil components and three surface waxes varied significantly between the leaf tip and remainder of the leaf. However, on plastic mimic leaves with uniform, non-foliar chemistry, eggs were still preferentially laid near `leaf' tips. Hence, leaf essential oils and surface waxes need not be involved in oviposition site choice. Observations of ovipositing beetles showed that they wrapped their tarsi around the leaf margin, suggesting that the ability to grasp the edges of a leaf may explain the oviposition pattern observed.

Keywords: essential oils; oviposition; surface waxes; Tasmanian eucalypt leaf beetle

Document Type: Research article

DOI: 10.1046/j.1440-6055.2003.00331.x

Affiliations: 1: Co-operative Research Centre for Sustainable Production Forestry, GPO Box 252−12, Hobart, Tas 7001, Australia. 2: School of Natural Resource Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Qld 4001, Australia.

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Role of foliar chemistry versus leaf-tip morphology in egg-batch placement by Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae)