Anthracnose, caused by Colletotrichum gloeosporioides and C. acutatum, is one of the main post-harvest diseases in guavas. This study aimed to determine the influence of environmental variables on germination and appressorium formation of Colletotrichum gloeosporioides and C. acutatum and infection of "Kumagai" guavas by these pathogens. The germination rate and the apressorium formation rate in vitro were determined under temperatures of 10, 15, 20, 25, 30, 35 and 40ºC, with wetting periods of 6, 12 and 24 hours. The infection of guavas was determined under temperatures of 15, 20, 25 and 30ºC and wetting period of 24 hours. There was no germination at 40ºC for either species. The germination and apressorium formation rate were rather high in the range of 15 to 30ºC for C. gloeosporioides, with a maximum at 25ºC. For the species C. acutatum, germination and apressorium formation rates were more sensitive to variations in temperature, with a maximum at 20ºC. The wetting periods tested somewhat influenced the germination of C. gloeosporioides, whereas in C. acutatum the germination was significantly lower with 6 hours of wetting than 12 and 24 hours. The infection of guavas, for both fungal species, increased with the temperature, unlike conidium germination and apressorium formation. Incidences of 100% occurred with 30°C, at 10 days after the inoculation.
Psidium guajava; anthracnose; germination; appressorium formation; post-harvest diseases
