Factors Affecting the Establishment and Survival of Anaitis efformata (Lepidoptera: Geometridae) Introduced into Australia for the Biological Control of St. John's Wort, Hypericum perforatum. I. Laboratory Experiments

(1) The geometrid moth, Anaitis efformata Guenee, a potential biological control agent for St. John's wort in south-eastern Australia, was found to have a thermal tolerance range of 7-5-30 IC, with optimal performance of growth, survival and fecundity in the 20-25 'C range. (2) An average of c. 800 D' > 7.5 'C is required for one complete generation, although this time can be significantly altered by the quality of larval food. A. efformata should survive and establish in all areas infested with St. John's wort, and should complete two generations per year in cooler regions and up to four generations in warmer regions. (3) Under optimal conditions, the population increase per generation was found to be c. 100 times. (4) Female A. efformata lay their eggs singly or in small clusters mainly in the top part of the host-plant and on the undersides of leaves. Small larvae are relatively immobile, but as they mature they migrate up the stems of St. John's wort and later down again to pupate in the soil. Larval survival is increased by the presence of prostrate basal foliage, which provides food and refuge for larvae dislodged from the upright stems. (5) About twenty larvae, surviving to maturity, are required to defoliate a 1 m length of St. John's wort stem. (6) The placement of synchronized pupae into weed-infested areas appears to be the most efficient method of release of A. efformata for field trials.