Meta-Analysis of the Effects of Triazole-Based Fungicides on Wheat Yield and Test Weight as Influenced by Fusarium Head Blight Intensity

Multivariate random-effects meta-analyses were conducted on 12 years of data from 14 U.S. states to determine the mean yield and test-weight responses of wheat to treatment with propiconazole, prothioconazole, lebuconazole, metconazole and prothioconazole+lebuconazole All fungicides led to a significant increase in mean yield and test weight relative to the check ((D) over bar : P < 0.001) Metconazole resulted in the highest overall yield increase, with a <(D)over bar> of 450 kg/ha, followed by prothioconazole+tebuconazole (444 5 kg/ha), prothiconazole (419 1 kg/ha), tebuconazole (272 6 kg/ha), and propiconazole (199 l kg/ha) Metconazole, prothioconazole+tebuconazole, and prothioconazole also resulted in the highest increases in test weight, with (D) over bar values of 17 4 to 19.4 kg/m3 respectively. On a relative scale, the best three fungicides resulted in an overall 13 8 to 15.0% increase in yield but only a 2.5 to 2.8% increase in test weight. Except for prothroconazole+tebuconazole, wheat type significantly affected the yield response to treatment, depending on the fungicide, (D) over bar was 110.0 to 163.7 kg/ha higher in spring than in soft-red winter wheat. Fusarium head blight (FHB) disease index (field or plot level severity) in the untreated check plots, a measure of the risk of disease development in a study, had a significant effect on the yield response to treatment, in that (D) over bar increased with increasing FHB index The probability was estimated that fungicide treatment in a randomly selected study will result in a positive yield increase (p(+)) and increases of at least 250 and 500 kg/ha (p250 and p500, respectively) For the three most effective fungicide treatments (metconazole, prothioconazole+tebuconazole, and prothiconazole) at the higher selected FHB index p(+) was very large (e g 0.999 for both wheat types) but p(500) was considerably lower (e g 0 78 to 0 92 for spring and 0 54 0.68 for soft-red winter wheat), at the lower FHB index. P-500 for the same three fungicides was 0 34 to 0 36 for spring only 0.09 to 0 23 for soft-red winter wheat