Table 1.
Chemistries and rates for nematicide treatments.
| Treatment abbreviation | Product | Active ingredient | Liters product/bedded haa | kg a.i./bedded ha | Method |
|---|---|---|---|---|---|
| 1. UTC | Untreated control | None | - | - | - |
| 2. MP-A | Metam KLRb | Metam potassium | 562 | 390 | Fumigation |
| 3. MP+FL | Metam KLR | Metam potassium | 562 | 390 | Fumigation (tank mix) |
| NIMITZc | Fluensulfone | 7.0 | 3.36 | ||
| 4. FL-A | NIMITZ | Fluensulfone | 7.0 | 3.36 | Ground spray |
| 5. 1,3-D | Telone IId | 1,3-dichloropropene | 75 | 88.3 | Fumigation |
Table 2.
Schedule for data collection and trial establishment. Numbers in parentheses are days before (negative) or after (positive) planting.
| Event | Year 1 (2019–2020) | Year 2 (2020–2021) |
|---|---|---|
| Preplant soil sampling | 18 Dec (−38) | 14 Dec (−30) |
| Nematicide application | 2 Jan (−25) | 18 Dec (−26) |
| Beds tilled and re-formed | 13 Jan (−14) | 5 Jan (−8) |
| Planting | 27 Jan (0) | 13 Jan (0) |
| Stand count 1 | 26 Feb (30) | 18 Feb (36) |
| Stand count 2 | 4 Mar (37) | 26 Feb (44) |
| Vigor rating 1 | 26 Feb (30) | 18 Feb (36) |
| Vigor rating 2 | 4 Mar (37) | 26 Feb (44) |
| Vigor rating 3 | 18 Mar (52) | 3 Mar (50) |
| Vigor rating 4 | – | 12 Mar (59) |
| Midseason soil sampling | 4 Mar (37) | 26 Feb (44) |
| Harvest soil sampling | 8 May (103) | 14 Apr (92) |
| Harvest | 11 May (106) | 21 Apr (99) |
Table 3.
Environmental conditions during the weeks before and after nematicide application for trials in 2019–2020 and 2020–2021
| Time Perioda | 2019–2020 | 2020–2021 | ||||
|---|---|---|---|---|---|---|
| Temperature (°C) | Temperature (°C) | |||||
| Rainfallb | Soilc | Air | Rainfall | Soil | Air | |
| 2 WBA | 7.54 | 16.9 | 16.0 | 0.53 | 16.3 | 12.0 |
| 1 WBA | 1.02 | 18.6 | 18.3 | 0.69 | 16.7 | 15.2 |
| Day of application | 0 | 16.8 | 16.5 | 0 | 14.9 | 7.3 |
| 1 WAA | 0.53 | 16.4 | 14.0 | 2.54 | 15.5 | 13.3 |
| 2 WAA | 0.00 | 18.4 | 21.1 | 0.25 | 14.3 | 13.9 |
| 3 WAA | 0.00 | 17.0 | 13.1 | 0.23 | 15.9 | 14.2 |
| 4 WAAd | 0.03 | 16.1 | 13.2 | 0.20 | 14.2 | 11.2 |
| 5 WAA | 1.42 | 16.3 | 15.4 | 0.13 | 13.3 | 11.3 |
| 6 WAA | 0.08 | 17.3 | 17.5 | 2.51 | 16.1 | 15.8 |
| 7 WAA | 0.86 | 18.5 | 18.1 | 0.51 | 13.4 | 11.1 |
| 8 WAA | 1.93 | 17.1 | 14.0 | 6.73 | 16.7 | 18.1 |
| 9 WAA | 0.20 | 16.9 | 16.4 | 5.66 | 18.2 | 17.7 |
| 10 WAA | 0.08 | 17.3 | 17.5 | 2.51 | 16.1 | 15.8 |
Figure 1:
Potato plant stand as affected by nematicide application in 2020 and 2021. Timing indicated in days after planting (DAP). Bars and brackets represent means (N=6) and standard errors, respectively. “UTC”, “MP-A”, “MP+FL”, “FL-A”, and “1,3-D” represent untreated control, metam potassium alone, metam potassium mixed with fluensulfone, fluensulfone alone, and 1,3-dichloropropene nematicide treatments, respectively. Within each subfigure, means with different letters are significantly different (Fisher’s protected LSD, α=0.05).
Figure 2:
Potato plant vigor and phytotoxicity during production 2020 as affected by nematicide application. Timing indicated in days after planting (DAP). Plant vigor is a visual rating on a 0–100 scale with 100 best. Bars and brackets represent means (N=6) and standard errors, respectively. “UTC”, “MP-A”, “MP+FL”, “FL-A”, and “1,3-D” represent untreated control, metam potassium alone, metam potassium mixed with fluensulfone, fluensulfone alone, and 1,3-dichloropropene nematicide treatments, respectively. Within each subfigure, means with different letters are significantly different (Fisher’s protected LSD, α=0.05).
Figure 3:
Reduced stand and plant vigor in metam+fluensulfone treatment (right) compared with untreated control (left) at 36 days after planting in 2020.
Figure 4:
Symptoms of phytotoxicity on emerging potato shoots in treatments with metam potassium alone or in combination with fluensulfone at 36 days after planting in 2020. There is browning at tips of shoots and leaf unfolding is delayed.
Figure 5:
Potato plant vigor during production in 2021 as affected by nematicide application. Timing indicated in days after planting (DAP). Plant vigor is a visual rating on a 0–100 scale with 100 best. Bars and brackets represent means (N=6) and standard errors, respectively. “UTC”, “MP-A”, “MP+FL”, “FL-A”, and “1,3-D” represent untreated control, metam potassium alone, metam potassium mixed with fluensulfone, fluensulfone alone, and 1,3-dichloropropene nematicide treatments, respectively. Within each subfigure, means with different letters are significantly different (Fisher’s protected LSD, α=0.05).
Figure 6:
Marketable and total yield as affected by nematicide application in 2020 and 2021. Marketable yield is USDA size A tubers without defects. Total yield includes marketable yield and culls due to size or quality. Bars and brackets represent means (N=6) and standard errors, respectively. “UTC”, “MP-A”, “MP+FL”, “FL-A”, and “1,3-D” represent untreated control, metam potassium alone, metam potassium mixed with fluensulfone, fluensulfone alone, and 1,3-dichloropropene nematicide treatments, respectively. Within each subfigure, means with different letters are significantly different (Fisher’s protected LSD, α=0.05).
Table 4.
Potato tuber yield (kg/ha) by grade and nematicide treatment.a
| Grade | Cb | B | A1 | A2 | A3 | Size cullsc |
|---|---|---|---|---|---|---|
| Nematicide Treatment | 2020 | |||||
| Untreated control | 805 | 1,408 | 4,965 b, c | 13,243 b, c | 451 | 2,213 |
| Metam potassium | 637 | 849 | 3,904 c | 10,613 c | 303 | 1,486 |
| Metam+Fluensulfone | 839 | 1,147 | 6,014 a, b, c | 14,429 a, b, c | 468 | 1,986 |
| Fluensulfone | 773 | 1,832 | 7,954 a, b | 17,112 a, b | 547 | 2,606 |
| 1,3-dichlorpropene | 1,039 | 1,969 | 8,948 a | 18,884 a | 54 | 3,008 |
| Nematicide Treatment | 2021 | |||||
| Untreated control | 1,394 a, b | 1,914 b | 6,934 | 7,782 c | 0 | 3,308 b |
| Metam potassium | 1,267 b | 1,940 b | 7,266 | 11,596 a | 0 | 3,208 b |
| Metam+Fluensulfone | 1,145 b | 1,763 b | 6,845 | 9,066 b, c | 0 | 2,908 b |
| Fluensulfone | 1,272 b | 1,998 b | 6,729 | 7,577 c | 0 | 3,270 b |
| 1,3-dichlorpropene | 1,585 a | 2,511 a | 7,645 | 10,886 a, b | 0 | 4,095 a |
a Different letters in the same column indicate significantly different means based on Fisher’s protected LSD at α = 0.05.
Table 5.
Weight (kg/ha) of tubers culled due to quality defects by category in 2021 season.a
| Nematicide Treatment | Rotted | Green | Growth crack | Misshapen | Total quality cullsb | Grand total cullsc |
|---|---|---|---|---|---|---|
| Untreated control | 469 a, b | 72 c | 443 | 305 | 1,289 | 4,598 b |
| Metam potassium | 237 b, c | 457 a | 575 | 291 | 1,561 | 4,768 b |
| Metam+Fluensulfone | 291 a, b, c | 299 a, b | 335 | 41 | 967 | 3,874 c |
| Fluensulfone | 145 c | 65 c | 941 | 168 | 1,319 | 4,590 b |
| 1,3-dichlorpropene | 545 a | 74 b, c | 1,127 | 37 | 1,782 | 5,877 a |
a Different letters in the same column indicate significantly different means based on Fisher’s protected LSD at α = 0.05. Due to COVID-19 restrictions, tuber defect culls were not measured in 2020
Figure 7:
Sting nematode soil population densities at preplant (before fumigation), midseason (37 to 44 days after planting), and harvest in 2020 and 2021 as affected by nematicide treatments. Bars and brackets represent means (N=6) and standard errors, respectively. “UTC”, “MP-A”, “MP+FL”, “FL-A”, and “1,3-D” represent untreated control, metam potassium alone, metam potassium mixed with fluensulfone, fluensulfone alone, and 1,3-dichloropropene nematicide treatments, respectively. Within each subfigure, means with different letters are significantly different (Fisher’s protected LSD, α=0.05). effects for a given season (ANOVA, P < 0.05).
Figure 8:
Stunt nematode soil population densities at preplant (before fumigation), midseason (37 to 44 days after planting), and harvest in 2020 and 2021 as affected by nematicide treatments. Bars and brackets represent means (N=6) and standard errors, respectively. “UTC”, “MP-A”, “MP+FL”, “FL-A”, and “1,3-D” represent untreated control, metam potassium alone, metam potassium mixed with fluensulfone, fluensulfone alone, and 1,3-dichloropropene nematicide treatments, respectively. Within each subfigure, means with different letters are significantly different (Fisher’s protected LSD, α=0.05).
Figure 9:
Free-living nematode soil population densities at preplant (before fumigation), midseason (37 to 44 days after planting), and harvest in 2020 and 2021 as affected by nematicide treatments. Bars and brackets represent means (N=6) and standard errors, respectively. “UTC”, “MP-A”, “MP+FL”, “FL-A”, and “1,3-D” represent untreated control, metam potassium alone, metam potassium mixed with fluensulfone, fluensulfone alone, and 1,3-dichloropropene nematicide treatments, respectively. Within each subfigure, means with different letters are significantly different (Fisher’s protected LSD, α=0.05).