Symptoms of Pythium root dysfunction (PRD) in creeping bentgrass are most common in the summer during periods of heat and drought stress. However, our observations indicate that Pythium volutum, a causal agent of Pythium root dysfunction, is most active during the fall and spring. Soil temperature thresholds for this pathogen must be determined so that preventative fungicide applications can be accurately timed. To determine the optimal temperature range for infection by P. volutum, ‘A-1’ creeping bentgrass was seeded into cone-tainers containing sand meeting USGA specifications and placed in the greenhouse. Eight weeks after seeding, plants were inoculated with one of 5 P. volutum isolates. After inoculation, the cone-tainers were transferred to growth chambers at constant 12C, 16C, 20C, or 24C (12 hr day/night cycles). After 4 weeks, the temperature in all chambers was increased to 32C/26C day/night to induce foliar symptoms. Typical PRD foliar symptoms developed in all infection temperature treatments two weeks after the temperature in all growth chambers was elevated to 32C/26C day/night. Severity of PRD was greatest when P. volutum infects creeping bentgrass roots at 16C. Reductions in root depth were not observed prior to raising the temperature to 32C/26C. However once the temperature was elevated, root dieback rapidly occurred. These results demonstrate that P. volutum is most active at temperatures prevalent during the fall and spring in NC, supporting our hypothesis that the majority of root infection occurs during this time.