The integrated use of planting date, fungicide seed treatment and crop rotation for improving the yield and profitability of field pea under root rot pressure

Dr. Michael Wunsch, Plant Pathologist, NDSU Carrington Research Extension Center

Collaborative field pea disease management research conducted by the North Dakota State University Carrington, Hettinger, and Williston research centers from 2014-2022 suggests that it may be possible to achieve commercially acceptable field pea yields under significant root rot pressure through the combined use of early planting, fungicide seed treatment, and a six-year crop rotation.

Planting field pea early conferred average yield gains of 4 to 8 bushels/acre across multi-year, multi-location studies conducted in fields with significant Aphanomyces and Fusarium root rot pressure.  In planting date studies conducted from 2017-2020 at Carrington and on-farm sites in west-central and northwestern North Dakota, root rot increased sharply with delays in planting.  Root rot severity was minimized when peas were planted into soils that averaged (across day and night) less than 50°F at 2 inches seeding depth in the 7 days after planting (Figure 1).  Consequently, yield also improved. Planting within these target soil temperatures is possible with knowledge of current daytime and nighttime temperatures combined with the current 7 to 10-day forecast.

Figure 1.  Data averaged across non-treated seed and fungicide-treated seed from 13 field trials conducted from 2017-2020.  Soil temperatures were assessed with data-logging sensors placed at seeding depth (2 inches) that recorded temperatures every 2 hours over the first 7 days after planting.  Peas were planted on three dates 10-14 days apart, generally mid/late April, early May, and mid-May.  Bar graphs show the average response relative to soil temperature observed across all studies.  Scatter plots show the relative performance of peas planted at a given soil temperature relative to the two other planting dates conducted in each study.

Use of a fungicide seed treatment conferred average gains of 4 to 6 bushels/acre in early-planted peas in the trials described above.  Seed treatments mitigated the emergence problems associated with planting into very cold soils (<45°F). Here the researchers observed strong, consistent gains when soil temperatures averaged less than 55°F (average, day and night, at a 2-inch depth) over the first 7 days after planting (Figure 2). All products (from all major manufacturers) that contained active ingredients with efficacy against Pythium and Rhizoctonia performed similarly. Tests performed in the laboratory, showed that the seed treatments helped against Aphanomyces and Fusarium at mid-vegetative growth. While no tests were performed for Pythium or Rhizoctonia, the strong response to seed treatment observed when soils were cool suggests that seed treatment and early planting may help against these pathogens as well.

Figure 2. Performance of non-treated seed versus seed treated with A) XtendC + Proline + Allegiance (0.38, 0.26, 0.25 fl oz/cwt) or B) Obvius (4.6 fl oz/cwt) in terms of field pea yield relative to soil temperature in the 7 days after planting.  Data are from field trials conducted from 2019 to 2022 in fields with elevated Fusarium and Aphanomyces root rot across four locations in North Dakota.  Bar graphs show the average response relative to soil temperature observed across all studies.  Scatter plots show the results from individual replicated studies or replicated planting dates within a planting date study.

In fields with a history of root rot, a 6-year crop rotation increases average field pea yield by 9 to 11 bushels compared to a 2- or 3-year rotation. In a long-term crop rotation study conducted in Carrington, ND commercially acceptable field pea yields (49 bu/ac) were obtained when a six-year rotation (pea/wheat/barley/canola/wheat/corn) was combined with fungicide seed treatment and early planting (Figure 3).  Peas were planted just as the first producers in the area were beginning to plant wheat and soil temperatures were between 45 and 50°F.  The six-year rotation (five years out of peas) had a 9-bushel yield gain compared to a 3-year rotation (pea /wheat /wheat), and an 11-bushel yield gain compared to a 2-year rotation (pea /wheat).  Crop rotation was critical for achieving satisfactory yields but insufficient as a stand-alone management tool.  In the same study, peas in the six-year rotation yielded 44 bu/ac without fungicide seed treatment (Figure 3).

Figure 3. Yield of field pea with and without fungicide seed treatment, in three different crop rotations. Peas were planted in a field with a severe root.

In summary, these experiments suggest that with a combination of early planting, fungicide seed treatment, and a six-year crop rotation, it is possible to obtain commercially acceptable field pea yields in fields that a history of Aphanomyces and Fusarium root rot. Researchers will build on these findings by investigating the combined impact of crop rotation interval, soil temperature, and use of a fungicide seed treatment.

A PDF with user-friendly slides illustrating major results from these studies is available on the NDSU Carrington Research Extension Center website.  Search for ‘NDSU Carrington Plant Pathology’ or navigate to

Acknowledgements: This research was a collaborative effort of Dr. Michael Wunsch (plant pathologist, Carrington), Dr. Audrey Kalil (plant pathologist, Williston), and John Rickertsen (agronomist, Hettinger) and their staff.  The research was made possible by grants from the Northern Pulse Growers Association, the ND Crop Protection Harmonization and Registration Board, and the USDA Specialty Crop Block Grant Program administered by the ND Department of Agriculture.

Contact Info:

Michael Wunsch, plant pathologist, NDSU Carrington Research Extension Center

663 Hwy. 281 North / PO Box 219 / Carrington, ND  58421-0219

701-652-2951 / Fax 701-652-2055 /

Published June 30, 2023