Biological efficiency of parasitoid wasp, Venturia canescens Gravenhorst in the feeding of the carob moth, Ectomyelois ceratoniae on various hosts

Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae) is an important parasitoid of lepidopterous pests, particularly the larval stage of Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae), which is a polyphagous and key pest. The host plant of the herbivore can have a significant effect on their parasitoids' biological properties and efficiency. Host plants have a direct impact on the biological parameters of the herbivores. Additionally, they can influence the development and reproductive characteristics of herbivores' natural enemies. The purpose of this study was to determine the effect of seven host plants on the life history of V. canescens, including apple, date, olive, orange, pistachio, pomegranate, and quince, as well as an artificial diet.

scanescens was grown on each host in a growth chamber set to 30±1°C, 60±5% RH, and photoperiods of 14:10 (L:D). Daily observations and records of stage duration, developmental period, and survival rate were made. The raw data were evaluated using TWO SEX-MSChart based on the age-stage, two-sex life table. Moreover, we used a spectrophotometer to determine the phytochemical metabolites of the tested hosts. Correlations between demographic variables and biochemical characteristics of various hosts were then estimated to identify factors affecting tritrophic interaction.

The results indicated that various hosts had a significant effect on the demographic characteristics of the V. canescens. The immature development period was the longest and shortest on quince and artificial diets, respectively. Additionally, V. canescens' intrinsic rate of increase (rm) was lowest on quince and highest on an artificial diet. Furthermore, significant differences in biochemical metabolites were observed in this study between the various hosts. Moreover, significant positive or negative associations were discovered between life history variables and the biochemical characteristics of various hosts. The time required for parasitoid development was positively correlated with the phenol, tannin, and flavonoid content of E. ceratoniae hosts tested. There was a significant negative correlation between the total phenolic content, tannins, and flavonoids of various hosts and the fecundity, net reproductive rate (R0), and intrinsic rate of increase of V. canescens.

Our findings may provide basic information for a comprehensive understanding of the tritrophic interactions between plants, herbivores, and parasitoids. Combining host plants and biological control agents may be an effective integrated pest management strategy for E. ceratoniae and other lepidopterous pests. Most importantly, our findings indicated that host plant quality variations could impact the performance and multitrophic communication behavior of V. canescens.