Parasitism and suitability of Aprostocetus brevipedicellus on Chinese oak silkworm, Antheraea pernyi, a dominant factitious host

Authors: WANG, JING - JILIN AGRICULTURAL UNIVERSITY; CHEN, YONG-MING - JILIN AGRICULTURAL UNIVERSITY; Yang, Xiangbing; LV, RUIE - JILIN AGRICULTURAL UNIVERSITY; DESNEUX, NICOLAS - NATIONAL COUNCIL FOR SCIENTIFIC RESEARCH-CNRS; ZANG, LIAN-SHENG - JILIN AGRICULTURAL UNIVERSITY

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2021
Publication Date: 8/2/2021
Citation: Wang, J.; Chen, Y.-M.; Yang, X.-B.; Lv, R.-E.; Desneux, N.; Zang, L.-S. Parasitism and Suitability of Aprostocetus brevipedicellus on Chinese Oak Silkworm, Antheraea pernyi, a Dominant Factitious Host. Insects 2021, 12, 694. https://doi.org/10.3390/insects12080694
DOI: https://doi.org/10.3390/insects12080694

Interpretive Summary: The wasp Aprostocetus brevipedicellus is an important egg parasitoid used in biocontrol programs for several forest pests. However, the mass rearing of Aprostocetus parasitoids remains little studied. Therefore, scientists from Jilin Agricultural University (China), Université Côte d’Azur (France), and the USDA-ARS (Miami, FL) evaluated the performance of A. brevipedicellus on a factitious host, Chinese silkworm Antheraea pernyi, to determine the host suitability for mass rearing. Five different host egg treatments were evaluated, including manually-extracted unfertilized washed eggs (MUW), naturally-laid unfertilized washed eggs (NUW), naturally-laid unfertilized unwashed (NUUW) eggs, naturally-laid fertilized washed eggs (NFW), and naturally-laid fertilized unwashed eggs (NFUW). The results showed that A. brevipedicellus can parasitize host eggs in all treatments, but there was a significant preference for MUW eggs compared to other treatments. Moreover, A. brevipedicellus preferred unfertilized eggs to fertilized eggs, and parasitized more washed eggs than unwashed eggs. The pre-emergence time of parasitoid from fertilized eggs was shorter than that from unfertilized eggs, and more parasitoids emerged from unwashed than from washed eggs. The offspring emergence rate was high (> 95%) and showed a female bias (>85%) among all egg treatments. Female parasitoids that emerged from MUW eggs had the highest egg load. The results indicate that A. brevipedicellus can be mass reared successfully on A. pernyi eggs and production can be optimized by using manually-extracted unfertilized washed eggs. This information will benefit action agencies that mass rear A. brevipedicellus for use in biological control programs.

Technical Abstract: Aprostocetus brevipedicellus, an egg parasitoid of the lepidopterous pests, is a potential biological control agent for control of many forest pests. Currently, a dominant factitious host, Antheraea pernyi, has been widely used for mass rearing of several parasitoids in China. However, whether A. pernyi egg is a suitable for A. brevipedicellus rearing remains unclear. Here we evaluated the parasitism of A. brevipedicellus and suitability of their offspring on A. pernyi eggs with five different treatments including manually-extracted unfertilized washed eggs (MUW), naturally-laid unfertilized washed eggs (NUW), naturally-laid unfertilized unwashed (NUUW) eggs, naturally-laid fertilized washed eggs (NFW), and naturally-laid fertilized unwashed eggs (NFUW). The results showed that A. brevipedicellus can parasitize host eggs in all treatments, but preferred significantly MUW eggs to other treatments. Moreover, A. brevipedicellus preferred unfertilized eggs to fertilized eggs, and parasitized more washed eggs than unwashed. The pre-emergence time of parasitoid from fertilized eggs (NFW: 22.19 d, NFUW: 21.71 d) was shorter than that from unfertilized eggs (MUW: 23.55 d, NUW: 23.92 d, NUUW: 24.14 d), and more parasitoids emerged from unwashed egg (NUUW: 8.31/egg, NFUW: 9.10/egg) than that from washed egg (MUW: 6.95/egg, NUW: 7.18 /egg, NFW: 7.91/egg). The offspring emergence rate was high (> 95%) and also female biased (>85%) among all egg treatments. The female parasitoids emerged from MUW eggs had the highest egg load. There were no significant differences in the hind tibia length and number of dead parasitoids per egg among the five treatments. Overall, the MUW eggs of A. pernyi are suitable for mass production of A. brevipedicellus.