Qualitative evaluation of damage by Epiblema strenuana (Lepidoptera: Tortricidae) to the weed Parthenium hysterophorus (Asteraceae)

Abstract

The North American Epiblema strenuana (Walker) may prove to be an important agent for the control of the weed Parthenium hysterophorus L. in Australia. In this article we report time-related changes in the galled shoots of P. hysterophorus consequent to attack by E. strenuana. In addition to many structural adjustments involving tissue regeneration, the host plant shows a number of metabolic alterations as a result of its response to galling by the moth larva. Through histochemical localization we demonstrate how the plant synthesizes some of the key metabolites facilitating the nutritional requirements of the larva and displays compensatory behavior to neutralize the stress induced by larval feeding. As the larva prepares for pupation, host-plant metabolism changes abruptly, by accumulating polyphenolic materials in the translocatory cells and ultimately blocking them. This event coincides with a modest decline in gall mass that was previously increasing with larval mass. The ability of the moth to damage the growth point, phloem, and the associated parenchyma, making them nonfunctional, and induce the plant to lose vigor, indicates that it is a potential biocontrol agent.