Canada thistle is a clone forming perennial weed that spreads aggressively and is difficult to control. One approach to managing invasive weeds is integrating numerous tactics instead of relying on a single tactic. Therefore, the objectives of this research were: 1) assess impacts of Hadroplontus litura, common sunflower competition, and soil nutrients on Canada thistle, and 2) investigate head capsule morphometrics and model H. litura developmental timing. Common sunflower competition, low soil nutrients, and H. litura herbivory negatively impacted aspects of Canada thistle growth and reproduction, but effects varied. Additionally, H. litura effects on thistle morphology were mild whereas the effects of soil nutrition and competition were persistent throughout the experiment. Histogram analysis and verification via Dyar’s rule produced adequate larvae categorization by instar number. Logistic thermal time models developed to predict mean developmental time were most accurate for first instar larvae and least accurate for egg stage.