Date of Award


Publication Type

Master Thesis

Degree Name



Biological Sciences


Biological sciences


Sherah Vanlaerhoven


David Hunt




Campoletis sonorensis is a native parasitoid of the Cabbage Looper, Trichoplusia ni, and I found it attacking T. ni in multiple field and greenhouse crops in Ontario. I found that C. sonorensis is an important factor regulating T. ni populations. Campoletis sonorensis was the dominant larval parasitoid of T. ni with higher rates of parasitism and higher abundances than all other native parasitoids combined. Campoletis sonorensis demonstrates potential as a commercial biocontrol agent of T. ni because C. sonorensis populations were chronologically and physiologically synchronized with those of T. ni. Thus, adult parasitoids were always available when suitable T. ni host stages were present. Additionally, C. sonorensis was a positively density-dependent factor in the regulation of the T. ni population. I demonstrated that C. sonorensis can successfully parasitise and emerge from 2 to 8 day-old T. ni hosts, but that the highest parasitoid fitness is achieved from 3 to 5 day-old T. ni hosts. Finally, C. sonorensis has a higher intrinsic rate of increase than T. ni, which is a desirable trait in potential biocontrol agents. Campoletis sonorensis is a native parasitoid that is very well adapted to T. ni population dynamics, but also attacks other Noctuidae host species. It appears that in the agricultural and climatic conditions of Ontario, the timing and presence of other Noctuidae host species may be an important factor in the stabilization of C. sonorensis populations, allowing it to be the dominant parasitoid species on T. ni.