We calculated the integrated UVB and plant damage irradiances for Argentina, a country in the Southern Hemisphere spread over a large latitudinal range. The irradiances were calculated for clear sky days using the Madronich code for the average conditions of the months corresponding to the summer and winter solstices and the fall and spring equinoxes. Ozone, aerosol and ground albedo typical for each region and for each period of the year have been considered. A comparison was made of the behavior of these irradiances at the different locations. A more pronounced time dependence of the plant damage irradiance was obtained because of the fact that the corresponding spectrum is largely concentrated at a small wavelength of the UVB interval. We established a correlation between both irradiances, which can be approximated by a quadratic function. Because the plant damage irradiance is a quantity that is not directly measured by instruments, we showed the utility of the correlation by determining this biological effectiveness from the integrated UVB irradiance measured at the Astronomical Observatory of Rosario, Argentina, on clear sky days of the year 2001, as a characteristic example of the midlatitude near–sea level location of a highly productive agricultural region, which can be extended to other regions of the world. The plant damage results are relative ones (as is the case for the erythemal irradiance). So, they can be used to determine the maximum/minimum and asymmetry ratios, to study the influence of atmospheric variables and to make comparisons with other geographical locations.