Examination of meteorology-based predictions of Fusarium head blight of wheat grown at two locations in the southern Pampas region of Argentina

In Argentina, head blight or scab is a highly risky disease ( caused by Fusarium graminearum) of wheat, although its occurrence is sporadic depending on prevalent environmental variables. These traits stimulated the development of predictive models of head blight epidemics, which would help growers in the selection of control strategies. Regression models for predicting head blight incidence were developed at Pergamino (33 degrees 56'S, 60 degrees 30'W), associating temperature and moisture variables with mean disease data (empirical approach). Recently a new fundamental-empirical approach for estimating Fusarium index (incidence% x severity%/100) was developed using data from Pergamino and Marcos Juarez (32 degrees 41'S, 62 degrees 07'W). Validation studies of both empirical and fundamental-empirical approaches were carried out at northern and southern locations showing good results after making a few changes. The objective of this work was to examine the goodness of fit of the predicted values from both approaches ( original and including some of the changes derived from previous validation studies) in comparison with median disease data in two southern locations of the Pampas region: Balcarce (37 degrees 45'S, 58 degrees 18'W) and Barrow (38 degrees 19/S, 60 degrees 15'W), for the 2002, 2003 and 2004 wheat seasons. Partial and mean deviation values between observed and predicted data were calculated. In accordance with previous validation studies, successful Fusarium index estimations were achieved decreasing the heat accumulation de. ning the length of the wheat critical period for infection to 450 degree days [base mean daily temperature (Td) = 10 degrees C]. Reducing the critical period length [450 degree days (base Td = 0 degrees C) instead of 530] and increasing maximum and minimum temperature thresholds (30 degrees instead of 26 degrees C and 11 degrees C instead of 9 degrees C) of the empirical equation thermal variable led to satisfactory Fusarium incidence predictions. This study showed that both approaches developed at northern locations of the Pampas region can be portable and useful for predicting disease intensity at more southern locations, making only a few changes. Differences in wheat cultivar behaviour regarding the disease were observed in the analysed data but this effect was not considered in this study.