2019 Soybean OVT Foliar Disease Evaluations: Maturity Group V

Tom Allen, Extension Plant Pathologist
By Tom Allen, Extension Plant Pathologist May 26, 2020 15:36

2019 Soybean OVT Foliar Disease Evaluations: Maturity Group V

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Field evaluations of the Maturity Group V entries in the MSU OVT were conducted at each of the locations where trials were planted (Brooksville (n=2), Clarksdale, Longwood, Olive Branch, Raymond, Stoneville (n=2), and Verona).  Entries were observed for their reaction to the diseases that occurred at each location. Cercospora blight, frogeye leaf spot (when present), Septoria brown spot, southern blight, and target spot were the most common diseases encountered at each location.  However, 2019, similar to the 2018 season, was not a good year for frogeye evaluations.  But, with that in mind, the limited amount of information as gathered are included since frogeye seems to be the main disease requested on an annual basis.  Be mindful that the ratings as presented are likely not as complete as they would be in a year when frogeye leaf spot produces more disease.  Plots were observed between R6 and R6.5.  Field evaluations for the presence of foliar disease were conducted using a 0 to 9 scale whereby 0=no disease and 9=excessive disease symptoms.  Cercospora leaf blight was evaluated based on the presence of disease on leaves (0 to 5), petioles (6), and on pods and stems (7 to 9) based on disease intensity as assessed by coloration of plant material (leaves with distinct purple coloration and petioles, pods and main stems with purple to near black coloration).  Septoria brown spot and target spot were evaluated in a similar fashion based on the presence of the disease within the plant canopy so that 0 to 3 indicated the presence in the lower canopy, 4 to 5 in the middle canopy, 6 to 8 in the upper canopy, and 9 indicative of extensive defoliation throughout the entire plant canopy and the disease in the upper most canopy.  Southern blight was based on the presence of the disease within the entire plot based on a 0 to 9 scale where 0=no disease, 5=approximately half of the plot exhibiting symptoms and 9=severe southern blight characterized by dead plants.  In a lot of cases, signs associated with southern blight (either white fungal growth or sclerotia) were observed at the base of infected plants.

Note that locations with a non-irrigated trial are marked as location (N) with an “N” in parentheses to indicate non-irrigated.

Maturity Group V Xtend (n=9 locations):

Cercospora blight MG V Xtend Cercospora blight

Frogeye leaf spot MG V Xtend frogeye

Septoria brown spot MG V Xtend Septoria

Southern blight MG V Xtend Southern blight

Target spot MG V Xtend Target spot

Maturity Group V Conventional (n=2 locations):

Cercospora blight MG V Conventional Cercospora blight

Frogeye leaf spot MG V Conventional frogeye

Septoria brown spot MG V Conventional Septoria

Southern blight MG V Conventional Southern blight

Target spot MG V Conventional Target spot

Maturity Group V Enlist/RoundUp Ready (n=9 locations):

Cercospora blight MG V RR Enlist Cercospora blight

Frogeye leaf spot MG V Enlist RR frogeye

Septoria brown spot MG V Enlist RR Septoria

Southern blight MG V Enlist RR Southern blight

Target spot MG V Enlist RR Target spot

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Tom Allen, Extension Plant Pathologist
By Tom Allen, Extension Plant Pathologist May 26, 2020 15:36
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