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. II. Field trials.
Life tables for Anaitis efformata [Aplocera efformata], a potential control agent for St. John's wort (Hypericum perforatum), were obtained by following the fate of eggs and larvae placed in the field on exposed potted plants during spring, summer and autumn in south-eastern Australia. Only 0.4, 0.7 and 1.6% of A. efformata individuals survived from egg to fully reproductive adult during these respective periods. The main causes of mortality were egg parasitism, failure of newly hatched larvae to establish and, most importantly, predation by a guild of generalist predators. Larval parasitism, several pathogens and competition with other herbivores produced smaller losses. Many of these agents could act in a density-dependent manner and suppress population build-up of A. efformata. Weather and food quality were also potential factors that could influence A. efformata population dynamics. Although these factors should not preclude establishment of A. efformata in Australia, they would most likely prevent populations of the moth from reaching levels which contribute significantly to the control of St. John's wort.