Host specificity and biology of the moth Psigida walkeri (Lepidoptera: Citheroniidae), a potential biological control agent for Mimosa diplotricha in Australia and the South Pacific

Abstract

Studies on the biology and host specificity of the citheroniid moth Psigida walkeri, native to Brazil and Colombia, were undertaken in Brazil and Australia. These studies were a component of a biological control project in Australia and the South Pacific for the invasive tropical weed Mimosa diplotricha. Biological studies focused on aspects of adult behavior, longevity, oviposition, and lifestage development. Host-specificity testing was undertaken on 110 plant species from 29 families, incorporating the family Mimosaceae and close relatives, and families containing economically important species. Twenty-nine of these plant species supported some degree of larval feeding. Psigida walkeri readily fed and developed for two or more generations on the known host plants M. diplotricha (=M. invisa), M. rixosa, M. velloziana, M. somnians, and on other test plant species M. pigra, Neptunia dimorpantha, and N. major. Therefore, these three additional species are considered potential hosts. Mimosa pudica, M. scabrella, and Acacia nilotica supported development of second generation larvae, but larvae were small, unthrifty, and eventually died. In choice tests, P. walkeri developed through to pupae and leaf consumption ranging from 10 to 100% on 5 bipinnate Acacia species, 5 Leucaena species, Calliandra calothyrsus, and Vigna unguiculata. These plant species could support larval development over one generation. There was no larval development beyond second instar in a series of no-choice tests; however, defoliation outbreaks could possibly occur on these 12 species from time to time. Due to the wide potential host range of this insect and especially the risk to native Australian Neptunia species, P. walkeri was not released in Australia.