Long-term rearing experiences influence parasitism ability of an ectoparasitoid wasp

Parasitoid wasps face increased mortality when paralyzing resistant hosts, involving host adaptation and biocontrol. This study investigates the plasticity of host adaptation in the ectoparasitoid Sclerodermus guani by examining how long-term rearing on hosts of differing resistance influences parasitism performance. Two distinct wasp lineages were established: the stressful Ma lineage, continuously reared on the highly resistant Monochamus alternatus (Ma) larvae, and the susceptible Sp lineage, continuously reared on the non-resistant Saperda populnea (Sp) larvae. Host preference assays revealed that Ma wasps exhibited a significant preference for Ma larvae, while Sp wasps favored Sp larvae. Although Ma wasps experienced higher mortality and a lower population increase index when reared on Ma larvae compared to the performance of Sp wasps on Sp larvae, they demonstrated superior parasitism efficiency when tested against resistant hosts. Specifically, Ma wasps had significantly lower mortality rates and higher population increase index than Sp wasps when both were tested on Ma larvae. In dual-parasitism trails, where 1 Ma wasp and 1 Sp wasp were introduced to the same Ma larvae, and in group trails involving 3 wasps from each lineage on the novel, high-resistant host Aromia bungii, the Ma wasps outperformed Sp wasps in paralysis success. Behavioral assays further indicated that Ma wasps invested more time in accessing host resistance but were quicker in locating hosts compared to Sp wasps. This research provides valuable insights for improving the design of mass rearing strategies to maximize the effectiveness of biological control agents in integrated pest management programs.