Resumen

BRAVO, V et al. Infection time by Dothiorella sp. and symptom onset of guava end rot. Rev. Fac. Agron. [online]. 2005, vol.22, n.4, pp.369-381. ISSN 0378-7818.

To determine the time of initial infection by Dothiorella sp. (Teleomorph: Botryosphaeria dothidea) in guava (Psidium guajava L.) fruits and the onset of disease symptoms, a field trial was installed three times (between December 1999 and July 2000). During 16 weeks, the following treatments were established weekly: 40 fruits covered and inoculated (FCI) with 3 mL/fruit of a conidia suspension, 40 fruits non covered and non artificially inoculated (FSCSI), and 40 fruits covered and non inoculated (FCSI), the latter one used as a treatment control. Seven days after inoculation, 20 fruits from each treatment were taken to the laboratory, disinfected, the pericarp cut in small segments, planted in agar V8-Juice and incubated for one month. The remaining 20 fruits of each treatment were left on the plants until the end of the trial, to observe the onset of disease symptoms. Significant differences (P<0,01), with regard to infection, were found among treatments and fruit age. Initial infection was observed at week 7 of fruit age, with 2.39% for FCI, and 19.05% for FSCSI. Infection increased progressively up to 100% (FCI) and 42.46% (FSCSI) in week 10. A low infection throughout the trial period (4.7 to 7.2%) was obtained in the control treatment (FCSI), due to contamination inside bags. First symptoms were observed in week 11, in treatment FCI (20%), and in week12, in FSCSI (15%) and FCSI (5%), increasing in the following weeks. Results show the critical stages in fruit and fungal development, which should be taken into account for disease prevention.

Palabras clave : Infection age; Botryosphaeria dothidea; macroscopic symptoms.