Sensibilidade de phakopsora pachyrhizi a fungicidas

Abstract

In most of Brazilian soybean producer regions, the asian soybean rust represent a menace, under favorable climatic conditions for the infection process. Ways of disease control are basically focused on the chemical control and on the management of inoculum sources. Information about the fungitoxicity of chemical substances, to Phakopsora pachyrhizi, would be of great interest to conduct work on the fungicide sensitivity. The objective of this work was to evaluate the sensitivity of P. pachyrhizi to the fungicides azoxystrobin, picoxystrobin, pyraclostrobin, trifloxystrobin, cyproconazol, epoxiconazol, flutriafol, metconazol, myclobutanil, tebuconazol and tetraconazol, in vitro and in vivo. Also, ideal substract, temperature, exposure time and photoperiod to P. pachyrhizi, in vitro, spore germination and uredospores germinative tube growth were defined. The agar-water substract was notorious at the in vitro testings; the ideal temperatures ranged from 20 to 25°C; the maximum uredospores germination ocurred with 6,4h of light exposure time and in the absence of light were observed the maximum germination and growth of the germinative tubes. The sensitivity of P. pachyrhizi uredospores, in vitro, was defined by the inhibition of germination and the inhibition of the germinative tube length. The addition of different concentrations of fungicides in agar-water methodology was used. The sensitivity of P. pachyrhizi, in vivo, was defined by the reduction in the number of lesions and the number of pustuls per unit of leaf area. The detached soybean leaf methodology was used. The IC50s values, determined in this work, may be used as reference data for future work of monitoring the sensitivity of P. pachyrhizi to fungicides