Evaluating dispersal ability of Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae) using natural abundance technique and geostatistics

Abstract

Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae), is one of the most serious insect pest worldwide. This research was done to evaluate the dispersal ability of Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae), as one of the larval parasitoids of this pest. The first trial was conducted at three plots consisting of 220 trees in each plot, which separating from each other by at least 100 m, and 13C-enriched V. canescens were released on a single tree at the center of each plot. The traps containing 50 larvae of E. kuehniella was attached at 6, 12, 18, and 24 m intervals in four directions of north, south, west, and east of the release tree. In the second trial, V. canescens were released from a tree where it located in central of each plot (n = 3, each plot = 0.3 ca). geostatistical tools and spatial analysis by distance indices (SADIE) was used to determine distribution of parasitoids in radii of 12, 24, 36 and 48m. Finally, semivariance analysis and isotope ratio indicated that the parasitoids had the highest density in 12 and 24 m radiuses after release while the spatial distribution in higher radii changed toward random or regular patterns. This result revealed that V. canescens could be a potential candidate for biological control of carob moth in pomegranate orchard and it would be attractive to develop the release points to 48 m from each other. Such information would be improved precision or site-specifc applications in agroecosystems and can also be used in site-specific pest management programs.