Food-Plant Spectrum and Elimination of Disease of Cinnabar Moth Larvae, Hypocrita jacobaeae (L.) (Lepidoptera: Arctiidae)

Abstract

The cinnabar moth, Hypocrita jacobaeae (L.), is the principal enemy of tansy ragwort, Senecio jacobaea L., in Europe. To determine if this moth could be safely liberated in Canada to control tansy ragwort, breeding stocks were imported as pupae from Sweden and Ireland for laboratory feeding tests. Larval feeding tests with various important economic plants before the moth was introduced to New Zealand from Britain (Cameron, 1935), to Australia from Britain (Currie and Fyfe, 1938), and to the United States from France (Parker, 1960) showed that the larvae would not survive on any of those tested. Such investigations specifically excluded certain crops from damage by the moth but did not indicate the range of plants that can be eaten. It is essential that an insect used in weed control should be highly restricted in its diet. If this restriction is related to nutrient discrimination, as described by Kennedy and Booth (1951) for Aphis fabae Scop., it would be necessary to screen many more economic plants than if it is related to “secondary” plant substances associated with a taxonomic group, as described by Fraenkel (1953). Thus, besides ad hoc tests on important plants, tests to determine the potential host spectrum of an insect are warranted before it is liberated against a weed. The plant spectrum of the cinnabar moth was determined by feeding the larvae on several genera in the tribe Senecioneae and representatives of most other tribes of Compositae that occur in Canada.