The asymptomatic host range of Fusarium virguliforme includes corn, a common crop rotated with soybean that we hypothesize may alter F. virguliforme population dynamics and disease management. A field-based approach explored the temporal dynamics of F. virguliforme colonization of corn and soybean roots under different tillage and residue managements. Experiments were conducted in IA, IN, MI, WI, and Ontario, Canada from 2016 to 2018. Corn and soybean roots were sampled at consecutive time points between 1 and 16 weeks after planting (WAP). DNA was extracted from all roots and analyzed by real-time qPCR for F. virguliforme quantification. Trials were rotated between corn and soybean, containing a two x two factorial of tillage (no-tilled or tilled) and corn residue (with or without) in several experimental designs. In 2016, low (ca. 100 fg/10 mg root tissue) F. virguliforme was detected in the inoculated IA, IN and MI locations, and non-inoculated WI corn fields. However, in 2017 greater levels of F. virguliforme DNA were detected in IA, IN and MI across sampling time points. Tillage practices showed inconsistent effects on F. virguliforme root colonization and SDS foliar symptoms among trials and locations. Yet, residue management did not alter root colonization of corn or soybean by F. virguliforme. Plots with corn residue had greater SDS foliar disease index in Iowa in 2016. However, this trend was not observed across the site-years, indicating corn residue may occasionally increase SDS foliar symptoms depending on the disease level, soil and weather factors.
