Foraging behavior of Venturia canescens Gravenhorst on potato tuber moth, Phthorimaea operculella Zeller

Venturia canescens Gravenhorst is one of the important parasitoids of lepidopterous pests with worldwide distribution. For assessing the efficiency of natural enemies in biological control, it is necessary to study their foraging behavior. In this study, host stage preference (between 1st and 4th instar larvae), functional response (densities of 2, 4, 8, 16, 24, 32, and 64 of 4th instar larvae), and mutual interference of V. canescens (densities of 1, 2, 4, 6, and 8 of wasps) were studied on potato tuber moth, Phthorimaea operculella Zeller, larvae. In the preference experiment, the 4th instar larvae of potato tuber moth were preferred by the wasp. The logistic regression analyses revealed that the functional response of V. canescens to the 4th instar larvae of potato tuber moth was type II. Searching efficiency (a) and handling time (Th) of the wasp were estimated 1.174 h−1 and 1.1347 h, respectively. In the mutual interference experiment, the per capita searching efficiency of the wasp ranged from 0.0810 to 0.1111 h-1, with the highest value at the density of 1 and 2 and the lowest value at the density of 8 wasps. The slope of regression line or interference coefficient was estimated to be -0.1356, indicating the mutual interference among the wasps. Based on the results, the foraging behavior of V. canescens was affected by the developmental stage and density of the host, as well as the density of the wasps. So, V. canescens has a good potential for IPM programs of potato tuber moth.