Biology and Host Range of Digitivalva delaireae (Lepidoptera: Glyphipterigidae), a Candidate Agent for Biological Control of Cape-ivy (Delairea odorata) in California and Oregon.

Cape-ivy (Delairea odorata Lemaire) is an ornamental vine native to South Africa that has escaped into natural areas in coastal California and Oregon, displacing native vegetation. Surveys in South Africa led to the discovery of the leaf- and stem-mining moth Digitivalva delaireae Gaedike and Kruger (Lepidoptera: Glyphipterigidae: Acrolepiinae) as one of several common and damaging native herbivores on Cape-ivy. In greenhouse studies, adult female life span averaged 16 d (46 d maximum). Most (72%) mated females began laying eggs within 72 h of emergence. Females had an average lifetime fecundity of 52 eggs, with >70% laid on leaf laminae, and 89% of eggs were laid by the 15th day postemergence. Lifetime fertility (adult production) averaged three to four offspring per female. At 25 °C, egg hatch required 10 d, pupal formation 26 d, and adult emergence 41 d, while under variable greenhouse and laboratory conditions development to adult required 54-60 d. In four-way choice tests, involving 100 plant species other than Cape-ivy, including 11 genera and 37 species in the Asteraceae, subtribe Senecioninae from both native and invaded ranges, D. delaireae inflicted damage and produced pupae only on Cape-ivy. Leaf mining damage occurred on 30% of leaves of native Senecio hydrophilus in no-choice tests and on 2% of leaves in dual-choice tests, but no pupation occurred. If approved for field release in the continental United States, the moth D. delaireae is expected to produce multiple generations per year on Cape-ivy, and to pose little risk of damage to native plants.

Laboratory host range of Parafreutreta regalis (Diptera: Tephritidae), a candidate agent for biological control of Cape-ivy.

Cape-ivy (Delairea odorata Lamaire) is an ornamental vine that has escaped into natural areas in many countries and become a serious pest. It is native to the eastern part of South Africa, and surveys there located several potential biological control agents for this weed. One of these is Parafreutreta regalis Munro, a tephritid fly that causes large galls to form on the stems of the vine. In a collaborative effort, we began to evaluate, in both California and South Africa, the host range of this fly. Between the two locations, we tested 93 plant species and 2 varieties of Cape-ivy to see if, after being exposed to four pairs of flies for a week, any galls would develop on them. No galls were formed on any of the test species, although an average of six galls developed on each of the Cape-ivy controls. We also tested to see whether P. regalis showed any preference for either of the two varieties of Cape-ivy. There was no significant difference between the numbers of galls forming on the stipulate or astipulate varieties. Our tests indicate that this fly is essentially monospecific. Earlier research had shown that P. regalis galls cause a significant reduction in the height and nongall biomass of Cape-ivy. A petition has been submitted to initiate the process of obtaining permission to release P. regalis in California to control the Cape-ivy infestations there.