Effects of climate on the introduction, distribution and biotic potential of parasitoids: Applications to biological control of California red scale

Abstract

California red scale (CRS) parasitoids of 121 citrus groves belonging to three different Mediterranean-climate ecosystems (inland, coastal and subtropical) of eastern Spain were used as a model to study the effects of climate on composition and distribution of parasitoid communities. Then we evaluate the success of a biocontrol program based on releases of three new CRS parasitoid species. Field surveys were complemented by laboratory trials under simulated common and extreme climate conditions (15, 20, 25 and 30°C combined with 25%, 45% and 65% RH) to know parasitoid’s life-history traits. In the inland area Aphytis melinus was the only parasitoid present, in the coastal it coexisted with Aphytis chrysomphali and in the subtropical also with Encarsia perniciosi. Comperiella bifasciata established in all inland groves where it was released whereas E. perniciosi and Aphytis lingnanensis only in the groves within the subtropical agroecosystem. In the laboratory, the highest intrinsic rate of increase (rm) values for C. bifasciata and E. perniciosi were reached at temperature–humidity regimes typical from inland and subtropical areas respectively. The longevity of both species at different temperature–humidity conditions also reflected their adaptability to dry or humid areas. Our results with CRS endoparasitoids, together with previous studies on Aphytis species, demonstrate the validity of rm analysis at different extreme temperature–humidity combinations to predict the potential areas of distribution of newly introduced organisms. Slight differences in average winter and summer temperatures or relative humidity between neighbor agroecosystems caused large variation in species composition and introduction success ratio.