Table 5.
Number of Cercospora leaf spot lesions observed on live spore traps (sentinel beets) placed in Michigan field studies in 2020, 2021, and 2022 (the year following fall-applied treatments).
| Trial Year | Treatment z | Sentinel y,x | |||||||
|---|---|---|---|---|---|---|---|---|---|
| May 26 – June 2 w | June 2 – June 9 | July 14 – July 21 | |||||||
| 2019-20 | Control | 5.5 | (284) | a | 4.1 | (60) | b | 5.3 | (199) |
| Plow | 5.4 | (337) | a | 3.9 | (51) | b | 5.4 | (219) | |
| Heat (1.6 kmph) | 4.0 | (65) | b | 2.5 | (16) | c | 4.7 | (130) | |
| Desiccant | 6.1 | (482) | a | 5.3 | (212) | a | 5.7 | (320) | |
| SE | 0.4 | 0.3 | 0.2 | ||||||
| P-values v | 0.0323 | * | 0.0063 | ** | 0.0653 | ||||
| LSD | 1.3 | 1.1 | - | ||||||
| June 1 – June 8 | June 15 – June 22 | June 29 – July 6 | |||||||
| 2020-21 | Control | 2.9 | (19) | 6.7 | (888) | ab | 7.3 | (1514) | |
| Plow | 2.0 | (9) | 6.3 | (628) | ab | 7.2 | (1397) | ||
| Heat (1.6 kmph) | 1.2 | (4) | 4.9 | (144) | c | 7.0 | (1189) | ||
| Desiccant | 2.1 | (15) | 7.0 | (1239) | a | 7.1 | (1222) | ||
| Heat (4.8 kmph) | 0.5 | (2) | 5.9 | (396) | b | 7.3 | (1498) | ||
| SE | 0.7 | 0.3 | 0.2 | ||||||
| P-values | 0.1128 | 0.0027 | ** | 0.8198 | |||||
| LSD | - | 0.8 | - | ||||||
| May 17 – May 24 | May 24 – May 31 | June 15 – June 22 | |||||||
| 2021-22 | Control | 5.1 | (166) | 6.4 | (614) | 5.7 | (358) | ||
| Heat (4.8 kmph) | 4.3 | (98) | 5.6 | (305) | 5.8 | (391) | |||
| SE | 0.4 | 0.2 | 0.4 | ||||||
| P-value | 0.1926 | 0.2238 | 0.7912 | ||||||
| LSD | - | - | - | ||||||
z Non-treated control, plow with a 3-m tandem disc set to invert soil 15 cm. immediately post-harvest, heat treatment using a propane-fueled burner (Multi-Trail Enterprises LLC) calibrated to heat foliage to 649-871°C at 1.6 kmph and 4.8 kmph prior to defoliation, and a desiccant (Sharpen 0.07 L/ha, methylated seed oil 1% v/v, ammonium sulfate 2037 g/L) applied seven days pre-harvest.
y Means generated under the lognormal distribution option in the GLIMMIX procedure (SAS v 9.4) of total CLS lesions counted on sentinel beets (USDA germplasm F1042) after 1-week exposure in the field, 3 d incubation in a 25°C humidity chamber, and 2 weeks in a greenhouse. (Non-normally distributed mean estimates shown in parentheses).
x Column values followed by the same letter were not significantly different based on Fisher’s Protected LSD (α = 0.05).
w Data shown for sampling weeks: 1st, 2nd, and 7th (2020); 2nd, 3rd, and 4th (2021); 1st, 2nd, 4th (2022). No or low detections in weeks not shown due to low spore concentrations or other external insect or drought stress factors ( Supplementary Table 1 ).
v Asterisk designations correspond to p-value thresholds<0.05 *,<0.01**.