Laboratory host range of Austromusotima camptozonale (Lepidoptera: Crambidae), a potential biological control agent of Old World climbing fern, Lygodium microphyllum (Lygodiaceae)

Abstract

Old World climbing fern, Lygodium microphyllum, is one of the most serious invasive weeds impacting south Florida and development of biological control is crucial for sustainable management. Larvae of a small moth, Austromusotima camptozonale, were discovered defoliating L. microphyllum in Australia. Preliminary testing suggested this moth was a Lygodium specialist. Laboratory host range testing was conducted on 65 species of test plants, from 31 families, comprising seven Lygodium species, four close relatives, 45 other species of ferns and fern allies, eight agricultural crops and one gymnosperm species plus the primary host L. microphyllum. Significant oviposition occurred only on other species of Lygodium. No eggs were laid on the agricultural crops, or about half the species of non-Lygodium ferns and fern allies tested. Oviposition on the other non-Lygodium ferns was very low, except on Anemia adiantifolia and Blechnum serrulatum, which received modest egg loads, but did not support development to adult. Larval feeding was low to non-existent on all the non-Lygodium species. Larvae developed to adult only on the native, American climbing fern L. palmatum, and to a lesser extent on L. japonicum. Lygodium japonicum is a naturalized invasive weed in the United States. Colonies of A. camptozonale were unable to persist on L. palmatum and died out in two to seven generations. Freezing winter temperatures in states where L. palmatum occurs would be lethal to A. camptozonale. It was concluded that A. camptozonale would pose no threat to native or cultivated plants in North America or the Caribbean and should be considered as a weed biological control agent against L. microphyllum.