M. Henrickson, John Bickel, Alyssa Betts
In the Mid-Atlantic region of the United States, Pythium root rot (PRR) of corn (Zea mays L.), caused by various oomycete species in the Pythium sensu lato (s.l.) genus, can be problematic under pathogen-favorable environmental conditions. Early season symptoms of Pythium infection in corn include pre- and post-emergence damping-off, stunting, and lesions on root or coleoptile tissue. Loss of seedlings from PRR can significantly reduce stand, but it is also possible for plants displaying early symptoms to survive the season. Limited data exists comparing the development and yield potential of surviving symptomatic plants to neighboring symptomless plants. Season-long effects of early season PRR were tracked in 16 paired symptomatic/symptomless sets in 2020 and 44 paired sets in 2021 from vegetative growth (V2-V3) through reproductive maturity (R6). In all cases, plant growth was delayed in the plants displaying symptoms of Pythium s.l. infection. Further, symptomatic plants had extrapolated yield reductions of 66%, which translates to losses of $13.80 per hectare ($5.60 per acre) for every 1% increase in symptomatic plants using a commodity price of $157.50 per metric ton ($4.00/bushel) of corn. While it has been understood that corn plants surviving early season Pythium s.l. infection have reduced vigor, this research provides the first quantification of estimated economic impact for the Mid-Atlantic region and informs management recommendations geared towards minimizing yield losses resulting from PRR.