|Abstract or Summary
- Tyria jacobaeae was introduced as a biological control agent to control the noxious weed Jacobea vulgaris. Eventually introduced to the Cascade mountain range of Oregon, T. jacobaeae has been found to feed on Senecio triangularis, a native plant closely related to J. vulgaris. Nosema tyriae is a parasitic fungus under the phylum Microspora (Microsporidians) and Tyria jacobaeae is the main host of the parasite (Canning et Al. 1999). Microsporidia infections of insect larvae exhibit slowed development, and increased mortality in both the larval and pupal stages.
Nutritional content of the host plant has been shown to increase the effect of the pathogen N. tyriae on T. jacobaeae. This increase can lead to greater mortality and decreased insect performance of T. jacobaeae on its non-target host S. triangularis (McEvoy et Al. 2008). The objective of this study was to determine the difference between pathogen infection levels on the two host plants T. jacobaeae and S. triangularis.
Based on previously documented higher mortality rates on S. triangularis (McEvoy et al. 2008), our hypothesis was that pathogens would multiply faster on S. triangularis than J. vulgaris and that the infection levels would increase in later stages with more time post-inoculation, and with greater spore dosages.
Host plant had no significant effect on levels of N. tyriae (intercept: χ² =30.2, df=1, P = 0.52) or disease progression (slope: χ² =1.09, df=1, P = 0.9). The effect of dose on disease progression was not significant (slope: χ² =3.4, df=1, P = 0.82), while the effect of dose on disease levels was marginally significant (intercept: χ² =212.6, df=1, P = 0.09).