![Alternative Methods to Manage Silverleaf Whitefly [Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae)] in Zucchini (Cucurbita pepo L.) Cover](https://paradigm-files.s3.eu-central-1.amazonaws.com/JOHR/cover-image.jpg)
Table 1.
Effect of plastic mulch color and row cover on plant growth, leaf whitefly index (WFindex), and zucchini fruit yield (Trial #1). Values are means ± SE, fall of 2019
| Treatment | Plant fresh wt (g) | Whitefly index1 | Marketable (1000 per ha) | Marketable (t per ha) | Fruit wt (g per fruit) |
|---|---|---|---|---|---|
| Mulch | |||||
| Black | 328 ± 34 | 3.0 | 101.3 ± 9.1 | 21.6 ± 2.6 | 208.0 ± 26.5 |
| White | 336 ± 36 | 3.2 | 131.8 ± 13.5 | 28.4 ± 3.3 | 216.8 ± 12.3 |
| Row cover | |||||
| Covered | 333 ± 32 | 1.8 b2 | 135.4 ± 11.0 | 28.1 ± 3.7 | 201.3 ± 12.9 |
| Uncovered | 331 ± 37 | 4.3 a | 108.6 ± 11.5 | 24.6 ± 1.9 | 236.0 ± 24.0 |
| Significance | |||||
| Mulch (M) | 0.882 | 0.972 | 0.180 | 0.298 | 0.845 |
| Row cover (C) | 0.971 | <0.002 | 0.094 | 0.360 | 0.218 |
| M × C | 0.667 | 0.994 | 0.829 | 0.820 | 0.706 |
Table 1A.
Effect of row cover on whitefly index (WFindex) odds ratio estimates and Wald confidence intervals in zucchini grown with row cover or uncovered, fall of 2019
| Odds ratio | Estimate | 95% confidence interval | |
|---|---|---|---|
| WFindex 2: With cover vs. Uncovered | 4.874 | 2.040 | 11.650 |
| WFindex 3: With cover vs. Uncovered | 2.181 | 0.608 | 7.819 |
Table 2.
Effect of plastic mulch color and particle clay applications on plant growth, leaf whiteflies index (WFindex), and marketable fruit yield in zucchini (Trial #2). Values are means ± SE, fall of 2019
| Treatment | Plant fresh wt (g) | WFindex | Marketable (1000 per ha) | Marketable (t per ha) | Fruit wt (g) | Leaf temperature (°C) | Mulch surface temperature (°C) |
|---|---|---|---|---|---|---|---|
| Mulch | |||||||
| Black | 521 ± 46 | 2.641 | 52.6 ± 2.9 b2 | 11.9 ± 0.9 b | 227 ± 11.9 | 36.9 ± 1.7 | 45.5 ± 2.6 |
| Gray | 509 ± 33 | 2.75 | 68.7 ± 5.0 a | 16.4 ± 1.6 a | 237 ± 11.4 | 36.2 ± 1.4 | 46.6 ± 3.1 |
| White | 462 ± 23 | 2.63 | 68.6 ± 5.9 a | 14.9 ± 1.5 ab | 217 ± 12.6 | 36.8 ± 1.2 | 46.8 ± 1.3 |
| Particle clay | |||||||
| Untreated | 488 ± 28 | 2.90 a3 | 58.0 ± 4.0 b | 13.0 ± 1.1 b | 225 ± 10.5 | 39.6 ± 0.9 a | 51.0 ± 1.4 a |
| Treated | 509 ± 32 | 2.44 b | 67.2 ± 4.2 a | 15.4 ± 1.2 a | 228 ± 9.3 | 33.7 ± 0.7 b | 41.5 ± 1.2 b |
| Significance | |||||||
| Mulch (M) | 0.508 | 0.708 | 0.007 | 0.018 | 0.468 | 0.737 | 0.798 |
| Particle clay (C) | 0.613 | <0.0001 | 0.032 | 0.035 | 0.645 | 0.0002 | <0.0001 |
| M × C | 0.990 | 0.079 | 0.335 | 0.069 | 0.092 | 0.865 | 0.188 |
1 WFindex (per leaf): 1 – no whiteflies, 2 – small number of whiteflies (< 250), 3 – medium number of whiteflies (250–500), 4 – high number of whiteflies (500–750), and 5 – extremely high number of whiteflies (> 750)
Table 3.
Effect of organic insecticidal solutions on plant growth, whitefly index (WFindex), and zucchini fruit yield (Trial #3). Values are means ± SE, fall of 2019
| Treatment | Plant fresh wt (g) | WFindex1 | Marketable (1000 per ha) | Marketable (t per ha) | Fruit wt (g per fruit) |
|---|---|---|---|---|---|
| Neem oil | 624 ± 74 | 2.7 ± b2 | 46.6 ± 3.9 a3 | 9.3 ± 1.0 a | 199 ± 10.4 |
| Soap | 631 ± 44 | 2.5 ± c | 34.1 ± 6.1 ab | 6.0 ± 1.3 ab | 181 ± 7.1 |
| Control (water) | 569 ± 49 | 3.7 ± a | 20.6 ± 5.7 b | 3.8 ± 1.2 b | 175 ± 22.1 |
| P | 0.693 | <0.0001 | 0.023 | 0.024 | 0.517 |
1 WFindex (per leaf): 1 – no whiteflies, 2 – small number of whiteflies (< 250), 3 – medium number of whiteflies (250–500), 4 – high number of whiteflies (500–750), and 5 – extremely high number of whiteflies (> 750)
2 Plants treated with neem oil had 604.14 times higher odds of showing fewer whiteflies than plants treated with water, where the 95% Wald confidence interval of the odds ratio was (30.73, >999.99). Plants treated with soap had over 999.99 times higher odds of showing fewer whiteflies than with water, where the 95% Wald confidence interval of the odds ratio was (122.31, >999.99). When comparing neem oil and soap, plants treated with soap had 7.03 times higher odds of showing fewer whiteflies than plants treated with neem oil. However, the confidence interval (1.07, 46.22) barely excluded 1
Table 4.
Effect of organic insecticidal solutions on plant growth, whiteflies index (WFindex), and zucchini fruit yield (Trial #3). Values are means ± SE, fall of 2020
| Treatment | Plant fresh wt (g) | WFindex1 | Marketable (1000 per ha) | Marketable (t per ha) | Fruit wt (g per fruit) |
|---|---|---|---|---|---|
| Neem oil | 777 | 2.7 b2 | 102 ± 2 | 16.6 ± 1.0 | 162 ± 9 |
| Soap | 717 | 2.6 b | 105 ± 6 | 16.8 ± 1.4 | 158 ± 7 |
| Control (water) | 602 | 4.1 a | 108 ± 8 | 17.0 ± 1.2 | 159 ± 6 |
| P | 0.283 | <0.0001 | 0.850 | 0.959 | 0.804 |
1 WFindex (per leaf): 1 – no whiteflies, 2 – small number of whiteflies (< 250), 3 – medium number of whiteflies (250–500), 4 – high number of whiteflies (500–750), and 5 – extremely high number of whiteflies (> 750)
2 Plants treated with neem oil had 135.69 times higher odds of showing fewer whiteflies than plants treated with water (95% Wald confidence interval of the odds ratio was 11.98, >999.99). Plants treated with soap had over 181.74 times higher odds of showing fewer whiteflies than plants treated with water (95% Wald confidence interval of the odds ratio was 15.54, >999.99). When comparing neem oil to soap, the odds of showing fewer whiteflies were not significant; the odds ratio was 0.75 [confidence interval (0.20, 2.84)]