Optimized pupal age of Tenebrio molitor L. (Coleoptera: Tenebrionidae) enhanced mass rearing efficiency of Chouioia cunea Yang (Hymenoptera: Eulophidae)

Performance of Chouioia cunea reared from a coleopteran alternative host as a biocontrol agent against the invasive lepidopteran pest, Hyphantria cunea

BACKGROUND

Chouioia cunea is a generalist pupal endoparasitoid. Native to Eurasia, the parasitoid has been mass-reared on an alternative lepidopteran host (Antheraea pernyi) to successfully control the exotic invasive lepidopteran pest Hyphantria cunea in China. To solicit more accessible hosts, this study evaluated the potential of an easily cultured coleopteran beetle (Tenebrio molitor) as a substitute for rearing C. cunea through comparing the relative performance of the parasitoids reared from both alternative hosts on H. cunea.

RESULTS

Compared with those reared from A. pernyi, the parasitoids reared from T. molitor (i.e., T. molitor vs. A. pernyi groups) performed equally well in terms of parasitism rate (94.4 vs. 88.9%), number of offspring produced per parasitized host (278 vs. 286), and female body length (1.334 vs. 1.351 mm), hind-tibia length (0.322 vs. 0.324 mm) and number of mature oocytes in the ovarioles (171 vs. 187), or even better based on offspring pre-emergence time (16.0 vs 16.9 days) and percentages of emerged offspring (99.8 vs. 99.1%) and female offspring (97.1 vs. 91.3%). Flight performance testing indicated that young C. cunea adults emerged from T. molitor had a similar percentage of actively flying wasps (76.9 vs. 72.9%) and a lower percentage of inactive wasps (2.3 vs. 10.6%) when compared to those reared from A. pernyi.

CONCLUSION

Given the remarkable adaptability of C. cunea and the vast availability of T. molitor as a common resource insect worldwide, this indigenous parasitoid could be mass-reared on T. molitor to improve the prospect of biological control of H. cunea in its invaded regions. © 2022 Society of Chemical Industry.

Parasitism and Suitability of Aprostocetus brevipedicellus on Chinese Oak Silkworm, Antheraea pernyi, a Dominant Factitious Host

Simple Summary

The egg parasitoid Aprostocetus brevipedicellus Yang and Cao (Eulophidae: Tetrastichinae) is one of the most promising biocontrol agents for forest pest control. Mass rearing of A. brevipedicellus is critical for large-scale field release programs, but the optimal rearing hosts are currently not documented. In this study, the parasitism of A. brevipedicellus and suitability of their offspring on Antheraea pernyi eggs with five different treatments were tested under laboratory conditions to determine the performance and suitability of A. brevipedicellus. Among the host egg treatments, A. brevipedicellus exhibited optimal parasitism on manually-extracted, unfertilized, and washed (MUW) eggs of A. pernyi, and A. brevipedicellus offspring emerging from MUW eggs had high egg load. The results indicate that MUW eggs are optimal for the mass production of A. brevipedicellus.

Abstract

Aprostocetus brevipedicellus, a eulophid gregarious egg parasitoid of lepidopterous pests, is a potential biological control agent for the control of many forest pests. A dominant factitious host, Antheraea pernyi, has been widely used for mass rearing several parasitoids in China. However, whether A. pernyi eggs are suitable for A. brevipedicellus rearing remains unclear. Here we evaluated A. brevipedicellus parasitism and fitness of their offspring on A. pernyi eggs with five different treatments, including manually-extracted, unfertilized and washed eggs (MUW), naturally-laid, unfertilized and washed eggs (NUW), naturally-laid, unfertilized, and unwashed (NUUW) eggs, naturally-laid, fertilized and washed eggs (NFW), and naturally-laid, fertilized and unwashed eggs (NFUW). The results showed that A. brevipedicellus could parasitize host eggs in all treatments but significantly preferred 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 offspring emerging from fertilized eggs was shorter than that from unfertilized eggs. More parasitoid offspring emerged from unwashed eggs than that from washed eggs. The offspring emergence rate was high (>95%) and also female-biased (>85%) among all egg treatments. The egg load of female parasitoid offspring emerging from MUW and NUW eggs was 30–60% higher than the remaining treatments. Overall, MUW eggs of A. pernyi are the most suitable for the mass production of A. brevipedicellus.

Recycling of spent mushroom substrate: Utilization as feed material for the larvae of the yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae)

Spent mushroom substrate is made from the waste remaining after the harvest of mushrooms. Here, we evaluated the potential of five spent edible fungi (Auricularia cornea, Lentinus edodes, Pleurotus eryngii, P. citrinopileatus and P. ostreatus) substrates as feed sources for Tenebrio molitor larvae. Young larvae did not survive on any substrate except the spent L. edodes substrate (36.7%). The survival rates in young larvae were similar among the different diets in which wheat bran or rice bran was replaced with 0, 20, 30, 40, 50, or 60% spent L. edodes substrate. The weights of the surviving larvae were decreased only when 70% of wheat bran and > 40% of rice bran was replaced with spent L. edodes substrate. In addition, the middle-aged larvae fed wheat bran only were significantly larger than those fed diets with 30~60% spent L. edodes substrate in dry feed, but the larvae of all treatments failed to pupate. Whereas the green feed was added in dry feed, there were no significant differences in pupal weight, pupation rate, pupal duration, adult emergence, or deformed adults among the three treatments in middle-aged larvae that were fed on diets containing 0, 30, or 40% spent L. edodes substrate. Collectively, these results suggest that spent L. edodes substrate has considerable potential to be used as a partial replacement (< 40%) of conventional feed for T. molitor, and spent mushroom substrate waste may be recycled as feed material for resource insects.