The effects of three regimens of cycling incubation temperatures and incubation at constant 25 degrees C on the growth of Fusarium graminearum NRRL 5883 and production of deoxynivalenol (DON) and zearalenone (ZEN) on rice were compared. The effects of low-temperature stress were also studied by incubating rice cultures at a constant 15 degrees C for 4 weeks following incubation at constant 25 degrees C for 2 weeks. Both incubation temperature and time significantly (P < or = 0.05) affected growth of F. graminearum NRRL 5883 and production of DON and ZEN. The highest amount of free ergosterol (640 microg/g culture material) that was used as a measure of fungal growth was found in cultures incubated at temperatures cycling between 15 and 30 degrees C during a 6-week period. The highest amounts of DON (1,679 microg/g culture material) and ZEN (603 microg/g culture material) were produced in cultures incubated at a constant 25 degrees C for 2 weeks prior to incubation at a constant 15 degrees C for an additional 4 weeks. Under cycling incubation temperatures, maximum amounts of DON (850 microg/g culture material) and ZEN (98 microg/g culture material) were produced in cultures incubated at temperatures cycling between 15 and 30 degrees C for 6 weeks. Overall, there was no correlation between mold growth and production of either DON or ZEN. However, DON production and ZEN production were correlated.