Parasitoid complex and biological suppression potential of Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae) against Pseudococcidae in vegetable cropping systems

Abstract:

Mealybugs belonging to Pseudococcidae represent one of the most damaging groups of sap-feeding insects affecting vegetable crops across tropical and subtropical agricultural regions. Among natural enemies, the solitary endoparasitoid Aenasius bambawalei Hayat has been identified as an effective biological control agent targeting Phenacoccus solenopsis Tinsley. How well this parasitoid performs across different vegetable hosts and seasonal windows remains insufficiently documented. This research was carried out in the coastal agricultural belt near Alexandria, Egypt, over two consecutive cropping cycles (March 2020 to February 2022) to evaluate the parasitoid complex linked to mealybug colonies on five vegetable crops: okra, eggplant, tomato, pepper, and squash. Field surveys involved fortnightly sampling from randomly selected quadrats within each crop block. Mealybug-infested plant parts were collected and maintained under controlled rearing conditions to recover emerging parasitoids. Identification relied on morphological keys and confirmation through taxonomic authorities. A. bambawalei was the dominant parasitoid recovered, representing 63.8% of all emerged specimens. Secondary parasitoids included Prochiloneurus bolivari and Anagyrus kamali at lower frequencies. Parasitism rates varied from 15.6% in squash to 47.2% in okra during the mid-season window. Seasonal fluctuation analysis revealed peak parasitoid activity between June and August, coinciding with high ambient temperatures and elevated mealybug densities. Biodiversity indices showed moderate species richness within the parasitoid guild, with Simpson diversity values ranging from 0.41 to 0.68 across crop habitats. A significant positive correlation was recorded between mealybug density and parasitoid emergence counts. The findings point to A. bambawalei as a promising candidate for augmentative biological control programs in vegetable cropping systems, particularly in okra where parasitism pressure was consistently highest.