Fusarium spp. are widely distributed throughout the word, infecting numerous crops including wheat and corn, and are known for their production of mycotoxins hazardous to humans and animals. Historically, Fusarium graminearum sensu stricto was thought to be the primary Fusarium species infecting wheat and corn in the midwestern United States. Over 560 isolates of Fusarium were collected from 121 fields in Michigan and identified to a species level, confirming numerous species besides F. graminearum are infecting wheat and corn in Michigan. While F. graminearum comprised 82% of recovered isolates, members of the Fusarium tricinctum complex were also identified in nine fields of wheat. In corn, members of the Fusarium fujikuroi species complex comprised 50% of isolates recovered. The largest proportion were F. subglutinans (33.3%). F. awaxy, a species not yet reported in corn in the U.S., was identified in six fields, comprising 4.6% of the collection. Isolates of F. graminearum collected were also genotyped to determine the type of trichothecene mycotoxins they produce. The large majority, 413 isolates (92%) were the 15-acetyldeoxynivalenol (15-ADON) type and twenty-six (6%) were 3-acetyl-deoxynivalenol (3-ADON). In addition, seven isolates (1.5%) were classified as the NX-2 chemotype. Interestingly, most of the NX-2 and 3-ADON isolates were found in the same region, from five fields in the far norther eastern part of the state with less intensive agricultural land use. Fungicides are an important tool in wheat and corn to manage Fusarium diseases and reduce toxin accumulation. Demethylation Inhibitor (DMI) fungicides have been widely used for the past 10-20 years in the state of Michigan. Here, we utilized our collection of Fusarium isolates to characterize in vitro fungicide sensitivity to three DMI chemistries (metconazole, tebuconazole, and prothioconazole). All EC50 values were below 4 μg/mL for F. graminearum, and sensitivity between the three chemistries was highly correlated. A field trial was established to investigate sensitivity in vivo with eight isolates of differing in vitro sensitivities. No differences in fungicide efficacy were observed. While there may not be practical resistance in Michigan currently, monitoring should continue as there is variation in in vitro sensitivities present within and among species of Fusarium. Work here also aimed to inform management of Fusarium head blight in wheat not only by characterizing the pathogen populations causing disease, but also through field trials investigating the response of winter wheat yields and Fusarium head blight to various inputs. A trial was established in East Lansing, MI (2014-2018) on soft white winter wheat cultivar ‘Ambassador’ to investigate the risks, benefits, and interactions of two nitrogen levels, three fungicide regimes, and a plant growth regulator trinexapac-ethyl. Presence and magnitude of response varied across years, as did disease pressure. In some years, the high nitrogen treatments had significantly higher fungal disease and lower yield compared to base nitrogen treatments. This trial also demonstrated that lodging due to high nitrogen rates can increasing Fusarium head blight incidence and foliar disease. In this trial and others, large variation in optimal fungicide regimes was observed. In order to evaluate which fungicide application timings or combination of timings were most effective over a large number of years, a meta-analysis of previously conducted fungicide trial data from Michigan was performed. Data from 46 trials from 2007-2020 was utilized to investigate six fungicide regimes. All regimes analyzed resulted in a mean positive yield response, and at least an 87% probability of a positive response in future applications. There were statistically significant differences between some regimes. Probabilities of positive yield response and prediction intervals were calculated for all regimes to aide growers in making future fungicide application decisions. Ultimately, the sum of this work will allow more precise management of Fusarium diseases in Michigan wheat and corn, by increasing our understanding of populations of Fusarium spp. causing disease and by estimating the impacts of nitrogen and fungicide inputs on yield and FHB management.
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