Four experiments were carried out at the FCAV-UNESP-Campus of Jaboticabal to evaluate the effect of temperature (15, 18, 20, 21, 24, 25, 27, 30, 33 e 35 + 1 ºC), and three light regimes (dark, continuous light and a 12/12 hour photoperiod) on the production of Guignardia citricarpa pseudothecia in citrus (Citrus sp.) areas of the States of São Paulo and Rio de Janeiro. In addition, the effects of those temperatures and periods of incubation (2, 8 and 16 h) on ascospore germination were also studied. Disks of Rangpur lime (Citrus limonia) leaves measuring 12 mm in diameter were autoclaved and transferred to Petri dishes containing 2% water-agar with the abaxial surface facing the medium. Four disks were placed in each plate equally spaced from each other. Two disks from colonies of Phyllostica citricarpa with 21 days of incubation were deposited in the center of each plate and incubated at the different temperatures. The effect of temperature on the photoperiod of 12/12 in the germination of ascospore of G. citricarpa was also evaluated. The generalized beta function was at 26, 22.5 and 27.5 ºC for conditions of darkness and light respectively. Pseudothecium production was observed in the photoperiod of 12/12 h. Mature ascospores were observed after 14 days of incubation, at 27 ºC. The highest percentage of germinated ascospores was obtained at temperatures around 24 ºC, after 16 h of incubation.
