Egg-age dependent parasitism by Trichogramma chilonis: implications for host-use pattern and strategy of parasitoid...

Understanding the relationship between the parasitism characteristics, development, and reproduction of parasitoids and host age is crucial for effective pest biocontrol. To optimize the biological control strategy of the potato tuber moth (PTM), Phthorimaea operculella, the parasitic behavior, host preference, offspring fitness, and glasshouse efficacy of a natural Trichogramma chilonis strain on PTM eggs of different ages were assessed.

Trichogramma chilonis successfully parasitized PTM eggs aged 24-108 h, but behavioral acceptance rate decreases significantly with increasing age. Younger eggs (24 h) were examined more quickly, while drilling and oviposition times were unaffected by age. In choice tests, T. chilonis preferred eggs aged 72 h or less, with no significant preference found in no-choice tests. Notably, offspring fitness was significantly reduced when parasitizing older eggs (96 h). Compared to T. chilonis offspring obtained from parasitizing 72 h eggs, those developing from 96 h eggs exhibited a 58.69% decrease in emergence rate and a 21.97% reduction in fecundity. Furthermore, the offspring were also smaller in size. Female body length, head width, and hind tibia length decreased by 8.88%, 10.27%, and 12.97%, respectively, with corresponding reductions in males were 6.11%, 8.39%, and 5.24%. Glasshouse trials further confirmed that T. chilonis parasitizes PTM eggs on plants, reducing emergence of PTM adults by 47.78%.

Trichogramma chilonis perform best on 24-72-h-old PTM eggs, and oviposition preference exhibits behavioral plasticity. This reveals the host-use pattern and oviposition strategy linked to offspring performance in T. chilonis, providing implications for its application in the biological control of PTM. © 2026 Society of Chemical Industry.