Medfly Population Suppression through Augmentative Release of an Introduced Parasitoid in an Irrigated Multi-Fruit Orchard of Central–Western Argentina

SIMPLE SUMMARY: Ceratitis capitata, commonly known as the Mediterranean fruit fly or medfly, is one of the most damaging invasive insect pests for fruit production and trade worldwide. Augmentative biological control (ABC) using parasitoids, insects whose larvae develop as parasites that eventually kill their hosts, is an eco-friendly strategy for medfly suppression and is used in several countries. This strategy relies on periodic releases of large numbers of mass reared parasitoids in an area where naturally occurring parasitoids are too few to control the target pest. ABC has been incorporated for 10 years into medfly suppression strategies in the irrigated fruit production valleys of San Juan province, northwestern Argentina, by the San Juan Fruit Fly Control and Eradication Program. In this study, we report the results of mass releases of the Southeast Asia-native parasitoid Diachasmimorpha longicaudata in a fruit farm from early summer (December) to mid-autumn (May) over two successive years. The effect of the released parasitoids on the suppression of the medfly population was evaluated based on captures of adult flies in food-baited traps, and the resultant levels of parasitism of fly larvae were assessed based on adult flies in sentinel fruit traps. Our results showed a substantial decrease in the medfly population on the parasitoid release farm. Therefore, ABC can be an effective tool for medfly control in San Juan. ABSTRACT: Biological control through the augmentative release of parasitoids is an important complementary tool that may be incorporated into other strategies for the eradication/eco-friendly control of pest fruit flies. However, not much information is available on the effectiveness of fruit fly parasitoids as biocontrol agents in semi-arid and temperate fruit-growing regions. Therefore, this study evaluated the effect of augmentative releases of the larval parasitoid Diachasmimorpha longicaudata (Ashmead) on Ceratitis capitata (Wiedemann) (medfly) populations over two fruit seasons (2013 and 2014) on a 10 ha irrigated fruit farm in San Juan province, central–western Argentina. The parasitoids were mass reared on irradiated medfly larvae of the Vienna-8 temperature-sensitive lethal genetic sexing strain. About 1692 (±108) parasitoids/ha were released per each of the 13 periods throughout each fruit season. Another similar farm was chosen as a control of non-parasitoid release. The numbers of captured adult flies in food-baited traps and of recovered fly puparia from sentinel fruits were considered the main variables to analyze the effect of parasitoid release on fly population suppression using a generalized least squares model. The results showed a significant decrease (p < 0.05) in the medfly population on the parasitoid release farm when compared to the Control farm, demonstrating the effectiveness of augmentative biological control using this exotic parasitoid. Thus, D. longicaudata could be used in combination with other medfly suppression strategies in the fruit production valleys of San Juan.