Efficacy and Stability of Integrating Fungicide and Cultivar Resistance to Manage Fusarium Head Blight and Deoxynivalenol in Wheat

Integration of host resistance and prothioconazole + tebuconazole fungicide application at anthesis to manage Fusarium head blight (FHB) and deoxynivalenol (DON) in wheat was evaluated using data from over 40 trials in 12 U. S. states. Means of FHB index (index) and DON from up to six resistance class-fungicide management combinations per trial (susceptible treated STR and untreated SUT; moderately susceptible treated MSTR and untreated MSUT; moderately resistant treated MRTR and untreated MRUT) were used in multivariate meta-analyses, and mean log response ratios across trials were estimated and transformed to estimate mean percent control () due to the management combinations relative to SUT. All combinations led to a significant reduction in index and DON (P < 0. 001). MRTR was the most effective combination, with a of 76% for index and 71% for DON, followed by MSTR (71 and 58%, respectively), MRUT (54 and 51%, respectively), STR (53 and 39%, respectively), and MSUT (43 and 30%, respectively). Calculations based on the principle of treatment independence showed that the combination of fungicide application and resistance was additive in terms of percent control for index and DON. Management combinations were ranked based on percent control relative to SUT within each trial, and nonparametric analyses were performed to determine management combination stability across environments (trials) using the Kendall coefficient of concordance (W). There was a significant concordance of management combinations for both index and DON (P < 0. 001), indicating a nonrandom ranking across environments and relatively low variability in the within-environment ranking of management combinations. MRTR had the highest mean rank (best control relative to SUT) and was one of the most stable management combinations across environments, with low rank stability variance (0. 99 for index and 0. 67 for DON). MSUT had the lowest mean rank (poorest control) but was also one of the most stable management combinations. Based on Piepho's nonparametric rank-based variance homogeneity U test, there was an interaction of management combination and environment for index (P = 0. 011) but not for DON (P = 0. 147), indicating that the rank ordering for index depended somewhat on environment. In conclusion, although the magnitude of percent control will likely vary among environments, integrating a single tebuconazole + prothioconazole application at anthesis with cultivar resistance will be a more effective and stable management practice for both index and DON than either approach used alone.