White mold severity in Michigan’s Thumb by variety

How did varieties stack up in their performance against white mold in 2014?

Cool, wet weather and morning fog in July and August 2014 made for ideal conditions for white mold development on soybeans across Michigan. Three of four Michigan State University Extension Thumb Ag Research and Education (TARE) soybean field trials were infected to the extent that comparisons could be made between varieties. Ratings were taken at trial sites in Elkton, Michigan, planted May 30; Fairgrove, Michigan, planted June 1; and Sandusky, Michigan, planted June 4.

The MSU Extension TARE plots include variety trials planted in three maturity groups: Group 1.9 and less (20 varieties), Group 2.0-2.2 (25 varieties), and Group 2.3+ (29 varieties). Trials in Fairgrove, Michigan and Sandusky, Michigan were replicated four times, and trials at Elkton, Michigan were replicated three times. Plots were 75 feet long and 15 feet wide and were planted in six 30-inch rows.

Varieties were scored for white mold severity on a 0-3 scale, where 0 = no infection, 1 = infection only on branches, 2 = infection on the main stem but pod fill was normal, and 3 = infection on the main stem resulting in plant death and poor pod fill. Three plants were inspected in 20 random spots in the center of each plot. The 20 scores were totaled and divided by 60 (the total if all 20 scores were given a rating of 3) and multiplied by 100 to give a disease severity index (DSI). A DSI of 100 would be given to a plot where all evaluated plants had a rating of 3. A DSI of 0 would be given to a plot where all evaluated plants had a rating of 0.

The planted population at the Elkton site was 160,000 seeds per acre. The planted population at the Fairgrove and Sandusky sites were 140,000 seeds per acre. The stand counts were 118,900; 128,950; and 122,630 respectively at the Elkton, Fairgrove and Sandusky sites.

Plots were rated during the second two weeks of September. Because of the wide range in maturity, plots ranged from growth stage R6 (full seed) to R8 (full maturity), with the majority in growth stage R7 (beginning maturity).

White mold pressure was variable between sites. Disease pressure was greatest at the Fairgrove site (moderate-heavy), followed by Elkton (moderate) and Sandusky (moderate-light). Disease pressure also tended to be variable within sites. For example, the northern end of the Sandusky plot (replications 3 and 4 of the Groups 1.9 and less and 2.0-2.3 studies) had virtually no white mold pressure. Hence, those two replications were not included in the DSI ratings. Finally, the late maturing varieties tended to be more severely infected than varieties within the medium and early studies, presumably due to the varieties flowering during peak stages of pathogen activity (i.e., spore release). The table below list the severity index for varieties within the early, medium and late maturity groups, respectively.

2014 White mold severity - MSU Extension TARE Soybean Variety Group 1.9 and less

Variety

Location

Elkton

Fairgrove

Sandusky

Average

Hyland Seeds HS 14RYS44

15.6

32.5

4.2

17.4

Mycogen 5B130R2

18.3

27.9

15.0

20.4

Stine Seed Company 14RD62

20.6

30.4

20.7

23.9

Hyland Seeds HS 15RYS45

35.0

25.0

17.5

25.8

NuTech Seed, LLC 7157 G2 Genetics

20.6

46.7

15.8

27.7

Great Lakes Hybrids 1441 R2

16.1

40.8

27.5

28.1

Croplan R2C1873

33.9

23.8

31.6

29.7

Great Lakes Hybrids 1689 R2

25.6

45.0

20.8

30.5

DF Seeds, Inc DF 51931 N R2Y

35.6

38.8

17.6

30.6

Croplan R2C1994

33.3

31.7

27.5

30.8

Rupp Seeds, Inc rs7184

30.6

29.6

36.7

32.3

Dairyland Seed Co DSR-1515R2Y

30.6

34.6

36.7

33.9

Dyna-Gro 34RY17

26.1

27.9

49.2

34.4

Hyland Seeds HS 18RY09

33.3

39.6

32.5

35.1

Syngenta Seeds NK Brand S19-Z9

38.9

26.7

40.8

35.5

Asgrow AG1835

40.6

43.3

24.2

36.0

Asgrow AG1832

33.3

45.8

31.7

36.9

Hyland Seeds HS 18RYS13

33.9

42.9

36.7

37.8

Great Lakes Hybrids 1829 R2

38.9

55.0

29.2

41.0

Asgrow AG1935

42.8

55.4

32.5

43.6

Average

30.2

37.2

27.4

31.6

2014 White mold severity – MSU Extension TARE Soybean Variety Group 2.0-2.2  

Variety

Location

Elkton

Fairgrove

Sandusky

Average

NuTech Seed, LLC 7216 G2 Genetics

38.3

40.8

5.0

28.1

Channel 2105R2

34.4

42.1

9.7

28.7

Croplan R2C2072

41.1

52.5

5.0

32.9

Channel 2108

47.2

42.1

20.2

36.5

NuTech Seed, LLC 7204 G2 Genetics

53.9

47.9

10.0

37.3

DF Seeds, Inc DF 5213 N R2Y

50.0

50.4

14.2

38.2

Great Lakes Hybrids 2039 R2

52.2

52.1

12.5

38.9

Stine Seed Company 22RD00

52.2

39.6

26.2

39.3

Dyna-Gro S20RY94

52.8

50.0

15.8

39.5

Asgrow AG2035

37.2

65.0

16.7

39.6

Syngenta Seeds NK Brand S20-T6

50.0

41.3

31.7

41.0

Mycogen Seeds 5N223R2

54.4

48.8

20.5

41.2

Mycogen Seeds 5N206R2

46.7

58.8

18.3

41.3

Dyna-Gro S20RY45

52.8

51.3

20.8

41.6

Syngenta Seeds NK Brand S22-S1

54.4

51.7

20.8

42.3

Great Lakes Hybrids 2289 R2

47.8

56.7

24.2

42.9

Asgrow AG2232

38.9

64.2

25.8

43.0

Dyna-Gro S22RY64

51.1

59.2

19.2

43.1

Rupp Seeds, Inc rs7222

51.7

58.3

22.5

44.2

Asgrow AG2031

45.0

56.7

31.7

44.4

Dairyland Seed Co DSR-2105R2Y

52.8

49.6

32.5

45.0

Hyland Seed HS 22RYS03

59.4

51.7

25.0

45.4

Stine Seed Company 20RD20

43.7

65.4

27.5

45.5

Great Lakes Hybrids 2019 R2

59.4

42.9

37.5

46.6

Croplan R2C2124

52.8

59.6

30.0

47.5

Average

48.8

51.9

20.9

40.6

2014 White mold severity - MSU Extension TARE Soybean Variety Group 2.6 and more

Variety

Location

Elkton

Fairgrove

Sandusky

Average

Beck’s Superior Hybrids 278R4

36.1

58.8

24.2

39.7

NuTech Seed, LLC 7261 G2 Genetics

24.4

63.8

40.8

43.0

Mycogen Seeds 2N263R2

35.6

69.2

25.4

43.4

Hyland Seeds HS 25RYS47

44.3

46.3

47.1

45.9

Dairyland Seed Co DSR-2612R2Y

36.7

73.3

30.0

46.7

Beck’s Superior Hybrids 241NR

45.6

62.5

35.4

47.8

Beck’s Superior Hybrids 229NR

39.4

70.4

39.2

49.7

Channel 2306R2

55.6

62.9

32.1

50.2

NuTech Seed, LLC 7233 G2 Genetics

53.9

56.7

41.7

50.7

Hyland Seeds HS 5A255RR2

34.4

64.2

54.2

50.9

Channel 2508

55.0

71.7

28.3

51.7

Great Lakes Hybrids 2469 R2

46.7

71.7

37.1

51.8

Stine 24RE03

50.0

55.4

51.3

52.2

Asgrow AG2632

39.4

68.3

49.6

52.5

Hyland Seeds HS 25RY05

51.1

69.2

38.3

52.9

Asgrow AG2433

37.2

80.0

41.7

53.0

NuTech Seed, LLC 7250 G2 Genetics

57.2

67.9

38.3

54.5

NuTech Seed, LLC 7240 G2 Genetics

55.0

65.0

44.2

54.7

Rupp Seeds, Inc rs7251

52.2

75.0

37.9

55.0

Dyna-Gro S25RY44

45.0

75.4

47.5

56.0

Dyna-Gro S24RY65

60.6

57.5

52.1

56.7

Dyna-Gro S26RY75

59.4

71.7

43.8

58.3

Great Lakes Hybrids 2319 R2

54.4

68.8

52.5

58.6

Rupp Seeds, Inc rs7245

51.7

81.3

44.2

59.0

Croplan R2C2394

60.6

64.2

53.8

59.5

Rupp Seeds, Inc rs7262

57.8

72.1

50.0

60.0

DF Seeds, Inc DF 5244 N R2Y

58.9

82.1

47.9

63.0

DF Seeds, Inc DF 5263 N R2Y

58.3

74.6

61.7

64.9

Hyland Seeds HS 26RYS16

58.7

74.2

63.3

65.4

Average

48.8

68.1

43.2

53.4

These results were not analyzed statistically. The results should be taken as a relative performance against white mold between varieties.

That being said, in the Group 1.9 and earlier varieties, the four varieties that appear at the top of the trial were generally less infected with white mold at each of the three sites, and the four varieties at the bottom of the table were generally more infected at each of the three sites. Likewise, the top three and the bottom three varieties in the 2.0-2.2 varieties were generally similar in infection levels at each of the three sites. Also, there is agreement in infection levels between the top four and bottom three varieties in the 2.3 and more trial.

Readers should not compare results between maturity groups. White mold infection levels varied between sites, and between studies at individual sites. The group 2.3 and more trial in Fairgrove was heavily infested, and the 1.9- and 2.0-2.2 studies at the Sandusky trial were lightly infested. So, a variety with an average DSI of 40 in the 1.9- group does not have the same level of white mold resistance as a variety with an average DSI of 40 in the group 2.3 and more trial.

The 2014 growing season is likely to stand out as one of the very worst years for white mold infections, and disease severity at these levels are unlikely to occur again for some time. Selecting varieties based on relative resistance to white mold is part of a strategy, including crop rotation, tillage choices, and use of fungicides in fields with a history of severe white mold. Growers are encouraged to seek out similar studies from other universities as well as industry data and compare results. 

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