Progress report for GW24-012
Project Information
Globodera pallida, the pale cyst nematode, is a quarantine potato pest detected in Idaho in 2006. Globodera pallida can cause yield loss of up to 80% in heavily infested fields and poses a major threat to the Idaho potato industry. Potatoes cannot be grown in the G. pallida infested fields and other non-host crops are not as profitable as potatoes. Alternative control strategies are needed due to the lack of G. pallida resistant russet potato varieties, the phase out of an effective fumigant methyl bromide, and the ability of G. pallida to survive in soil for decades in absence of a host. The purpose of this study is to evaluate the efficacy of biofumigants as an alternative strategy of G. pallida control. Biofumigation strategy utilizes glucosinolate-containing Brassica plants to suppress diseases and pests. Previous research has demonstrated the effectiveness of Brassica juncea seed meal extract (SME) to control G. pallida. Furthermore, prior treatment with 4-hydroxybenzyl alcohol (HBA) increased the efficacy of B. juncea SME. Since HBA is one of the hydrolysis products of Sinapis alba seed meal, the impact of the combination of B. juncea and S. alba will be investigated under greenhouse and field conditions. Treatments will also include the allyl isothiocyanate-based biofumigant ‘TerraMG.’ The results of this project will be presented to the stakeholders through presentations and a newsletter. If proven effective, biofumigants would provide a less environmentally toxic option for G. pallida control.
Research Objectives:
- Determine the impact of Brassica juncea seed meal extract (SME) in combination with Sinapis alba to control Globodera pallida in greenhouse using post-treatment egg viability and hatch assays.
- Evaluate how biofumigants affect Globodera pallida hatch and reproduction in comparison to Brassica juncea SME under field conditions.
Educational Objectives:
- Present research findings on the efficacy of biofumigants on Globodera pallida to stakeholders at professional meetings.
- Publish a stakeholder newsletter in layman’s terms explaining the findings on the biofumigants and its potential as an alternative tool for Globodera pallida eradication.
- Publish a video that provides stakeholders with an overview of Globodera pallida containment techniques used in field research.
Cooperators
- - Producer
Research
Research Objectives:
- Determine the impact of juncea seed meal extract (SME) in combination with S. alba to control G. pallida in greenhouse trials using post-treatment egg viability and hatch assays.
- Evaluate how biofumigants affect pallida hatch and reproduction in comparison to B. juncea SME under field conditions.
Objectives 1 Approach
Two trials were conducted in the magenta vessels in an incubator maintained at 20 ºC to evaluate the effect of different rates of S. alba seed meal and B. juncea SME on G. pallida egg viability and hatch. A combination of B. juncea SME (0 or 250 lbs/acre) with five rates of S. alba seed meal (0, 92, 184, 368, and 4000 lbs/acre) were tested. Two treatment application times were also tested- i) S. alba for 2 weeks followed by B. juncea for an additional 2 weeks ii) and S. alba seed meal together with B. juncea SME for 4 weeks. Treatments were arranged in a randomized complete block design with 6 blocks for each treatment. A 2:1 sand to soil mixture sterilized by autoclaving twice was used for the experiments. Globodera pallida cysts placed into 2.54-cm2 wear-resistant nylon mesh bags were hydrated in sterile distilled water for 3 days and used to infest soil at a rate of 5 eggs per gram of soil. The treatments were applied at appropriate rates to the pots inoculated with G. pallida. Untreated controls did not receive any treatment. The magenta vessels were watered to facilitate the hydrolysis of glucosinolates and covered with lids for 4 weeks. After 4 weeks, bags containing cysts were retrieved, surface sterilized with 0.3% hypochlorous bleach and used for hatching and viability assays to assess the impact of the treatments on G. pallida. The experiment was repeated.
The effect of treatments on G. pallida egg hatch was determined by exposing eggs to potato root diffusate (PRD) for 2 weeks. PRD was collected from the potato cultivar ‘Russet Burbank’ after 4 weeks of growth under greenhouse conditions. Three G. pallida cysts from each treatment replicate were crushed in 100 ml sterile distilled water in 96-well plates (one cyst per well). The numbers of eggs and second stage juveniles (J2s) in each well were counted and 100 ml of PRD was added. After 2 weeks, the number of hatched J2 was counted and the percentage hatch was calculated by using the formula: egg hatch (%) = [(number of 2-week J2 − number of initial J2)/number of initial eggs] × 100.
The effect of treatments on G. pallida egg viability was assessed using acridine orange staining (Pillai & Dandurand, 2019). Globodera pallida eggs were exposed to acridine orange dye for 4 hours followed by washing with water to remove excess dye. The number of stained and non-stained eggs were counted using a fluorescent microscope. Percent egg viability was calculated using the formula: egg viability (%) = (non-stained eggs/stained eggs + non-stained eggs) x 100.
Objective 2 Approach
The field experiments were conducted at the research site situated within a G. pallida infested field near Shelley, Idaho. To contain and prevent spread of G. pallida, field trials were conducted in microplots made of 19 liters plastic buckets (Dandurand et al., 2017). The microplots were infested at an initial infestation rate of 3 eggs per gram soil using G. pallida cysts contained in nylon mesh bags. Treatments included B. juncea SME and S. alba seed meal mixture, TerraMG, B. juncea SME only, S. alba seed meal only, and untreated control. Experiments were set up in a randomized complete block design with 6 blocks for each treatment. Treatments were applied to the microplot buckets and covered with lids for 4 weeks. To conduct egg hatch and viability assays as outlined above for greenhouse trials, one cyst bag was removed after 4 weeks of treatment. The G. pallida infestation rate in each microplot after removing one cyst bag was about 2.5 eggs/gram soil. A susceptible potato variety, ‘Russet Burbank,’ was planted in the microplots containing the remaining cysts to assess the effect of treatments on G. pallida reproduction. Two tubers per microplot were planted and grown for 12 weeks. The microplots were irrigated as needed and fertilized biweekly during the maintenance trips. After 12 weeks, plants were terminated, soil was dried and G. pallida cysts were extracted using elutriator from soil samples (2 kg) in the greenhouse facility at the University of Idaho. The number of progeny cysts and eggs were counted and reproduction factor was determined. The experiment was repeated.
Experimental data was analyzed by analysis of variance using PROC GLM statement in Statistical Analysis Software (SAS) and treatments were considered significantly different at P ≤ 0.05. The data reported are averages ± SEM.
Research results Year 1
Objective 1: Determine the impact of B. juncea seed meal extract (SME) in combination with S. alba to control G. pallida in greenhouse trials using post-treatment egg viability and hatch assays.
Globodera pallida cysts were exposed to B. juncea SME alone or in combination with five rates of Sinapis alba seed meal and their effect on G. pallida egg viability and egg hatch was determined. Compared to untreated control, B. juncea SME significantly reduced G. pallida egg viability and egg hatch by 16 and 94%, respectively. Of the rates of S. alba tested, only the lowest rate (92 lbs/acre) significantly increased egg hatch by 51% compared to the untreated control. The increase in hatch by S. alba is expected due to the hydrolysis product of sinalbin present in the seed meal. Additionally, we found that the highest rate of S. alba tested significantly reduced the viability and hatch of G. pallida eggs compared to the untreated control. When compared to the untreated control, the G. pallida egg hatch and viability were not significantly impacted by any other S. alba rates tested. For S. alba, we used seed meal which contains sinigrin along with other nitrogen and carbon compounds in addition to the predominant glucosinolate sinalbin. When a higher rate of S. alba was used, a higher concentration of these additional chemicals may have contributed to reduced egg viability and hatch rates. Furthermore, the combined application of B. juncea SME with S. alba seed meal did not significantly reduce G. pallida egg viability and hatch compared to B. juncea SME alone. Regarding timing of application, results showed that the application of S. alba seed meal together with B. juncea SME for 4 weeks resulted in a 26-75% greater reduction in egg viability and hatch compared to applying S. alba seed meal for 2 weeks followed by B. juncea SME for an additional 2 weeks. The reduction was statistically significant for 184 and 368 lbs/acre of S. alba seed meal. This implies that a longer exposure duration to B. juncea (4 weeks) may have a more significant effect than a short exposure duration (2 weeks).
Objective 2: Evaluate how biofumigants affect G. pallida hatch and reproduction in comparison to B. juncea SME under field conditions.
To test the effect of different biofumigants and their combinations, two field trials were conducted. Results from both trials are reported. The treatments used in the field experiment are shown in table 1 below.
Table 1: Treatments used in the field experiment
|
Treatments |
Rates |
|
Untreated control |
No treatment |
|
Sinapis alba seed meal only |
92 lbs/acre |
|
Brassica juncea seed meal extract (SME) only |
250 lbs/acre |
|
S. alba seed meal + B. juncea SME |
S. alba meal= 92 lbs/acre B. juncea SME= 250 lbs/acre |
|
TerraMG Part A only |
42 gal/acre |
|
TerraMG Part A + S. alba meal |
TerraMG part A = 42 gal/acre S. alba seed meal = 92 lbs/acre |
|
TerraMG Part A + Part B |
15 gal/acre |
|
TerraMG Part A + Part B |
42 gal/acre |
a. Effect of the treatments on pallida egg viability and hatch
The effect of treatments on G. pallida egg viability and hatch is shown in Table 2 and Table 3, respectively. Brassica juncea SME significantly reduced G. pallida egg viability and hatch compared to the untreated control. Sinapis alba only significantly reduced G. pallida egg viability by 31% and 30% in trial 1 and trial 2, respectively compared to the untreated control but did not significantly reduce egg hatch. A combination of S. alba seed meal and B. juncea seed meal extract (SME) significantly reduced G. pallida egg viability and hatch compared to the untreated control. However, the reduction was not significantly different than by B. juncea alone. The application of TerraMG part A only did not significantly reduce egg viability compared to the untreated control. TerraMG part A applied together with S. alba meal or Part B containing myrosinase enzyme significantly reduced G. pallida egg viability in both trials compared to the untreated control. Both rates of TerraMG tested significantly reduced G. pallida egg viability and hatch compared to the untreated control.
Table 2: Effect of biofumigants on G. pallida egg viability under field conditions.
|
Treatments |
Egg viability (%) ± SEM |
|
|
Trial 1 |
Trial 2 |
|
|
Untreated control |
65.13 ± 2.48 a |
59.18 ± 1.78 a |
|
S. alba meal only @92 lbs/acre |
45.20 ± 0.95 b |
41.12 ± 2.47 b |
|
B. juncea SME only @250 lbs/acre |
49.46 ± 1.48 b |
36.49 ± 1.67 bc |
|
S. alba @92 lbs/acre + B. juncea @250 lbs/acre |
47.58 ± 2.26 b |
35.96 ± 1.74 bc |
|
TerraMG- A @42 gal/acre only |
63.13 ± 2.88 a |
54.93 ± 2.05 a |
|
TerraMG A @42 gal.acre + S. alba meal |
44.94 ± 0.94 b |
34.20 ± 1.61 cd |
|
TerraMG @ 42 gal/acre |
47.02 ± 1.62 b |
29.73 ± 1.65 d |
|
TerraMG @ 15 gal/acre |
50.38 ± 3.59 b |
31.87 ± 1.57 cd |
Values within same column followed by a common letter are not significantly different (P ≤0.05).
Table 3: Effect of biofumigants on G. pallida egg hatch under field conditions.
|
Treatments |
Egg hatch (%) ± SEM |
|
|
Trial 1 |
Trial 2 |
|
|
Untreated control |
38.81 ± 6.61 a |
44.19 ± 10.99 ab |
|
S. alba meal only @92 lbs/acre |
35.23 ± 7.46 a |
44.59 ± 4.54 a |
|
B. juncea SME only @250 lbs/acre |
17.00 ± 2.88 b |
14.39 ± 2.57 cd |
|
S. alba @92 lbs/acre + B. juncea SME @250 lbs/acre |
18.28 ± 2.77 b |
17.05 ± 1.81 c |
|
TerraMG- A @42 gal/acre only |
18.39 ± 2.21 b |
31.17 ± 3.05 b |
|
TerraMG A @42 gal.acre + Sa meal |
14.79 ± 3.52 b |
11.34 ± 0.90 d |
|
TerraMG @ 42 gal/acre |
16.36 ± 3.71 b |
12.49 ± 1.56 cd |
|
TerraMG @ 15 gal/acre |
14.01 ± 3.28 b |
15.45 ± 1.33 cd |
Values within same column followed by a common letter are not significantly different (P ≤0.05).
b. Effect of the treatments on pallida reproduction on a susceptible potato
In-field bioassay was done to assess the effect of treatments on reproduction. In trial 1 bioassay (Table 4), compared to untreated control, a combination of S. alba seed meal and B. juncea SME significantly reduced the number of progeny cysts by 66% compared to the untreated control. Similarly, TerraMG at 42 gallons/acre SME significantly reduced the number of progeny cysts by 96% compared to the untreated control. TerraMG at 42 gallons/acre also significantly reduced the reproduction factor by 97% compared to the untreated control. No other treatments significantly reduce the progeny cysts or reproduction factor. In this trial, potato plant growth was poor in microplots due to spider mite infestation, and some plants died prematurely. This resulted in high variability and low number of progeny cysts and reproduction factor overall.
In trial 2 (Table 5), B. juncea SME and both rates of TerraMG significantly reduced the number of progeny cysts and reproduction factor compared to the untreated control. Addition of S. alba to B. juncea or TerraMG Part A further reduced the number of progeny cysts and Rf compared to B. juncea or TerraMG alone.
Table 4: Effect of biofumigants on G. pallida reproduction (progeny cysts and reproduction factor) in field trial 1
|
Treatments |
#Progeny cysts |
Rf (Pf/Pi) |
|
Untreated control |
38.83 ± 9.60 a |
0.21 ± 0.05 a |
|
S. alba meal only @92 lbs/acre |
25.94 ± 10.26 ab |
0.14 ± 0.06 ab |
|
B. juncea SME only @250 lbs/acre |
18.10 ± 7.28 ab |
0.08 ± 0.03 ab |
|
S. alba @92 lbs/acre + B. juncea SME @250 lbs/acre |
13.18 ± 5.18 b |
0.06 ± 0.03 ab |
|
TerraMG- Part A @42 gal/acre only |
23.00 ± 9.03 ab |
0.13 ± 0.06 ab |
|
TerraMG Part A @42 gal.acre + S. alba meal |
6.54 ± 4.25 ab |
0.04 ± 0.02 ab |
|
TerraMG Part A @ 15 gal/acre + Part B |
3.85 ± 3.85 ab |
0.02 ± 0.02 ab |
|
TerraMG Part A @ 42 gal/acre + Part B |
1.33 ± 1.33 b |
0.01 ± 0.01 b |
Values within same column followed by a common letter are not significantly different (P ≤0.05).
Table 5: Effect of biofumigants on G. pallida reproduction (progeny cysts and reproduction factor) in field trial 2
|
Treatments
|
#Progeny cysts |
Rf (Pf/Pi) |
|
Untreated control |
218.75 ± 29.33 a |
1.12 ± 0.21 a |
|
S. alba meal only @92 lbs/acre |
233.75 ± 18.72 a |
1.21 ± 0.14 a |
|
B. juncea SME only @250 lbs/acre |
61.25 ± 9.76 b |
0.27 ± 0.04 c |
|
S. alba meal + B. juncea SME @250 lbs/acre |
35.00 ± 11.40 c |
0.17 ± 0.06 d |
|
TerraMG Part A only @42 gal/acre |
267.50 ± 40.60 a |
1.30 ± 0.20 a |
|
TerraMG Part A @42 gal/acre + S. alba meal |
10.00 ± 3.16 d |
0.05 ± 0.01 e |
|
TerraMG Part A @ 15 gal/acre + Part B |
107.50 ± 25.15 b |
0.54 ± 0.13 b |
|
TerraMG Part A @ 42 gal/acre + Part B |
15.00 ± 5.12 c |
0.08 ± 0.03 cd |
Values within same column followed by a common letter are not significantly different (P ≤0.05).
In summary, results suggest that B. juncea SME at 250 lbs/acre is effective to reduce G. pallida egg viability, hatch and reproduction. Addition of S. alba seed meal did not further reduce egg viability and hatch after 4 weeks but reproduction on ‘Russet Burbank’ potato after 12 weeks of growth significantly reduced in field trial. This effect on reproduction at the end of the growing season is the most important aspect because the second-stage juveniles weakened by the activity of biofumigants may hatch out of the eggs but may not be able to complete their life cycle. This may also indicate that a longer exposure to isothiocyanate may be beneficial to achieve a greater impact on G. pallida. Also, TerraMG, a liquid product derived from mustard seed, is made up of two-part formula. Part A is a sinigrin formulation and part B consists of enzyme myrosinase. Mixing both parts is necessary to release isothiocyanate and reduce G. pallida egg viability, hatch and reproduction as indicated by results from the field trials. Both rates of TerraMG tested were found to be effective against G. pallida.
Research Outcomes
Our experiments show that B. juncea applied at a rate of 250 lbs/acre is effective in suppressing G. pallida hatch and reproduction and there is potential to further reduce its reproduction by combining it with S. alba seed meal. TerraMG at both rates also showed promising results in reducing G. pallida. Since environmental concerns from chemical fumigants have led to more restrictions on their use, growers dealing with G. pallida infestation may find these alternatives to be a useful tool. Higher reduction of G. pallida by combining B. juncea and S. alba could be crucial where the goal is to eradicate this pest. Furthermore, it is important to note that the effect of these biofumigants may be observed several weeks after exposure. Also, we used S. alba seed meal in our experiments. Using formulated seed meal extracts with a higher sinalbin concentration may further reduce the amount of product needed to achieve higher efficacy.
Education and Outreach
Participation Summary:
Education Objectives:
- Present research findings on the efficacy of biofumigants on G. pallida to stakeholders at professional meetings.
Results were presented to growers and MustGrow team in Spring 2025.
- Publish a stakeholder newsletter explaining the findings on the biofumigants and its potential as an alternative tool for G. pallida eradication.
- Publish a video that provides stakeholders with an overview of G. pallida containment techniques used in field research.
Recorded video footages of field microplot set up during 2024 field season.
Education Objectives:
- Present research findings on the efficacy of biofumigants on G. pallida to stakeholders at professional meetings.
Presented at a meeting including MustGrow team and growers in Spring 2025. Results and potential field applications were also discussed. Now that we have complete data from lab and field experiments, these findings will be presented in professional meetings in 2025 and 2026.
- Publish a stakeholder newsletter explaining the findings on the biofumigants and its potential as an alternative tool for G. pallida eradication.
- Publish a video that provides stakeholders with an overview of G. pallida containment techniques used in field research.
A draft of a video explaining the G. pallida field experiment set up and containment protocols has been prepared from the 2024 field season. More video footage is being recorded during this (2025) field season. These videos will be added to the 2024 field season footage and published later in the summer of 2025.