We tested the effects of larval age and stress on the susceptibility of the convergent lady beetle (Hippodamia convergens) to the weakly pathogenic bacterium Pseudomonas fluorescens. To test for the effects of larval age, the dose response to the bacterium was determined for each instar. The LC₅₀s for first, second, and third instars (4.8 × 10⁹, 2.8 × 10¹⁰, and 3.9 × 10⁹ CFU/ml, respectively) were not significantly different from each other, but the LC₅₀ for fourth instar larvae was 40 times greater at 3.2 × 10¹¹ CFU/ml. To test for the effects of stress, first instar larvae were maintained at one of two temperatures (25 or 30°C) for 18 hr and were given one of three diets (water, sucrose solution, or aphids) for 24 hr before being exposed to the pathogen. Larvae maintained at 25°C and fed aphids (the optimum diet) had the highest susceptibility with an LC₅₀ of 4.8 × 10⁹ CFU/ml. The least susceptible larvae were those maintained at 25°C and fed only water, with an LC₅₀ of 7.3 × 10¹¹ CFU/ml, i.e., starvation increased resistance 150-fold. Temperature had a significant effect on the dose response only for the water diet treatment, decreasing the LC₅₀ from 7.3 × 10¹¹ CFU/ml at 25°C to 8.9 × 10⁹ CFU/ml at 30°C. These results suggest that some stressors, such as poor diet, may decrease the susceptibility of H. convergens to P. fluorescens, whereas certain combinations of stressors, such as starvation and high temperature, have an interactive effect that then increases susceptibility.