Comparison of single- or multi-active ingredient fungicides for controlling Fusarium head blight and deoxynivalenol in Brazilian wheat

In this study, we gathered data on Fusarium head blight (FHB) severity, deoxynivalenol (DON), and wheat yields from 19 cooperative fungicide trials conducted in Southern Brazil over five growing seasons (2017-2021). We tested three premixes of Quinone Outside Inhibitors (QoIs) + demethylation inhibitors (DMIs) (PYRAclostrobin + METConazole, TEBUconazole + TriFLoXystrobin, and TriFLoXystrobin + PROThioconazole), one triple premix of QoI + DMI + succinate dehydrogenase inhibitors (SDHI) (TriFLoXystrobin + PROThioconazole + BIXaFen), and two single active ingredients (METC [DMI] and CARBendazim [benzimidazole; MBC]) applied three times, beginning at the flowering stage and continuing every 7-12 days. We fitted a network meta-analysis model to the log of the means of FHB index and DON content data and to the non-transformed mean yield for each treatment, including the untreated control. Disease (FHB index) reduction estimates ranged from 41.5% (TEBU + TFLX) to 62.8% (METC); the latter did not differ from PYRA + METC (56.1%). Likewise, the mean estimates of percent DON reduction were higher for METC (65.1%) and PYRA + METC (58.3%). These two treatments were followed by TEBU + TFLX (50%), which was not statistically different from CARB (48%) and TFLX + PROT (45.2%), but differed from TFLX + PROT + BIXF (39.3%). Lastly, the yield response was higher for TFLX + PROT + BIXF (643 kg/ha), which differed from all other treatments, including METC (505.9 kg/ha), PYRA + METC (477.8 kg/ha), TFLX + PROT (455.3 kg/ha), CARB (453.2 kg/ha), and TEBU + TFLX (403.4 kg/ha). The results of this metaanalysis are crucial for choosing fungicides when planning programs aimed at reducing both FHB and DON levels in wheat.