Effects of egg position, host arrangement and rearing space on the efficiency of a new mass‐rearing method for the parasitoid Dastarcus helophoroides

Abstract BACKGROUND Dastarcus helophoroides (Coleoptera: Bothrideridae) is an effective natural enemy against longhorn beetles in China. However, the high cost of rearing, resulting from laborious traditional artificial methods, is the primary obstacle to applying this natural enemy in biological control programs. An efficient rearing system for D. helophoroides was developed, which reduces the rearing costs, by adjusting the rearing space, horizontal or vertical placement of rearing tubes, and parasitoid placement. RESULTS The arrangement of rearing tubes significantly affected the parasitism rate, the mean number of cocoons, and the mean number of emerged adults, while it did not significantly affect the total developmental duration or the mean adult weight of the parasitoid. In contrast, the rearing box sizes and egg card placement had no significant effects on these parameters. CONCLUSION These findings suggest that the rearing efficiency of D. helophoroides can be maximized by using medium‐sized rearing boxes, horizontally arranged rearing tubes, and peripherally placed egg cards. Our findings provide a scientific basis for further optimizing the mass‐rearing technology of this parasitoid. © 2025 Society of Chemical Industry.