Progress 09/01/22 to 08/31/23
Outputs
Target Audience:The target audience is strawberry growers and industry partners, especially commercial fumigation companies and grower associations, pest control advisors and industry groups such as the California Strawberry Commission, North American Strawberry Growers Association and participants at the Methyl Bromide Alternative Outreach meeting. Changes/Problems:We did not receive the machines from Norway in time to test in 2023. The Konflex steam applicator is not well designed for strawberry and will be tested in raspberries. Additionally, the Konflex machine arrived damaged and will not be operational until repaired which will likely occur in November 2023. What opportunities for training and professional development has the project provided?(1) Graduate Student Training (1 graduate student and 1 post doc were trained on the project (one at UC Davis, one at NCSU)) (2) Grower education (four extension meetings were conducted: Two in CA and two in NC). One postdoctoral scientist and one research technician worked on this project, which enhanced their background in field and laboratory research. (3) A mobile SIOUX steam generator that was used at NCSU between 2020 and 2022 for field trials was successfully transferred to Penn State University. How have the results been disseminated to communities of interest?Results were presented at the MBAO conference in 2022 and at an extension meeting in 2023 to over 200 attendees. What do you plan to do during the next reporting period to accomplish the goals?A steam applicator from Konflex in The Netherlands was shipped over in November 2022 and we are further evaluating the use of that machine. We have invited Soil Steam International from Norway to bring their new steam applicators for testing in 2024.
Impacts
What was accomplished under these goals?
Soil disinfestation with steam is an alternative to soil fumigation, but there have been limited attempts to scale-up steam application for field use in strawberry. The objective of this work is to determine if spot steam application in the strawberry planting hole is sufficient to protect strawberry roots from soilborne pathogens and weeds. Five studies were initiated in California in Oxnard, Salinas and Watsonville during summer-fall 2022. All sites were placed in areas known to have infestations of soilborne strawberry pathogens. Each trial used a spot steam applicator with three 25 cm long injectors per hole. The device was set up to treat four planting holes per injection. Each plot had 32 planting holes. Treatments were steam and no steam. Treatments were replicated 6 times and arranged in a randomized complete block. Steam was injected to raise the soil temperatures to 70 to 80°C, which was generally accomplished within 60 to 90 seconds. Soil samples were collected before and after steam application and subjected to appropriate lab assays. Spike steam injections suppressed Macrophomina phaseolina, Fusarium oxysporum, Pythium spp. and weeds. Fruit yields were highest in steamed plots compared to the control for the Oxnard summer planting, but at the Spence and Watsonville winter planted trials, fruit yields were only marginally improved with soil steaming. NC field trials were established in the past reporting cycles (2020-2022). Those field trials investigated the weed and pathogen control efficacy of AITC, Quicklime and Siodium Peroxide in combination with low-pressure soil steam applications. Results showed that AITC in combination with steam did not improve weed or pathogen control, compared to AITC alone. However, steam in combination with quicklime did significantly improve weed and pathogen control, compared to steam alone treatments. Findings were shared at two grower meetings (NC Pre-plant meetings) in 2023, and published in peer-reviewed journals. Five studies were initiated in 2022 in California at Oxnard, Salinas and Watsonville. All sites were placed in areas known to have infestations of strawberry diseases. Each trial used a spot steam applicator with three 25 cm long injectors per planting hole. The device was set up to inject steam through the plastic mulch into columns of 25 cm diameter x 25 cm depth (10 inches x 10 inches) and into four planting holes simultaneously. Each plot had 32 planting holes. Treatments were steam and no steam. Treatments were replicated 6 times and arranged in a randomized complete block. Steam was injected to raise the soil temperatures to 70 to 80°C, which was generally accomplished in 60 to 90 seconds. Soil temperature was monitored using HOBO data logger sensors (Onset computers) inserted into each treated bed. Soil samples (500g) were collected before and after steam application (0 - 25 cm deep) in both treated and non-treated control plots from 16 planting holes (composite) per plot and subjected to appropriate lab assays. Bare-root strawberry transplants of cultivars known to be susceptible to resident pathogens were planted in holes in all plots. Weed densities were assessed in both treated and non-treated plots by counting the number of weeds in planting holes. Plant mortality was assessed by counting the number of dead and live plants in both treated and non-treated plots. Fruit yields were recorded at commercial harvest intervals. Data were analyzed in JMP 16.0.0 and ARM 7.0. Mean separation was performed using Tukey's HSD for pathogen densities in soil and independent sample t-test for weed densities and fruit yield. Duration of soil temperatures > 70°C in the steam-treated holes ranged from 14 - 76 min. Populations of Fusarium oxysporum in the soil at the Oxnard site were reduced by 79% in the steam treatment. At Watsonville, steam application reduced Macrophomina phaseolina densities in the soil by 100%. At River Road and Spence 1 trials, Pythium species were detected, and steam application reduced this pathogen by 99% for both trials. Steam reduced plant mortality by 90 and 100% at Oxnard at two assessments. Spike steam reduced weed densities in all 5 trials. At Oxnard fruit yields were greatly improved by steam, but at Salinas 1 and Watsonville, yield improvements were marginally better with steam compared to the control. At the Spence 2 trial, fruit yields were highest in the Pic Clor 60 treatment followed by steam and then the control. The significant reduction in plant mortality and improved yield from steam at the Oxnard site is most likely due to the higher disease pressure plants experience during a summer-planted trial when soil and air temperatures are more conducive to charcoal rot disease development. In comparison, yield and plant mortality data showed no significant difference between treatments in the winter planted Salinas and Watsonville trials.
Publications
- Type:
Conference Papers and Presentations
Status:
Awaiting Publication
Year Published:
2023
Citation:
1. Fennimore SA, Rachuy RS, Henry P, Daugovish O, Ivors K, Broome JC, Chinganda C 2023. Soil Pest Control in Strawberry with Strategic Steam Placement. In: Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Volk, E., Neal, J., Fennimore, SF., Fox, G. and Hoffmann, M. 2023. Weed and pathogen control efficacy of steam combined with quicklime and sodium peroxide. North American Strawberry Grower Meeting, San Luis Obispo, CA. March 2023. Oral Presentation.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2023
Citation:
Volk, E., Jennings, K., Fennimore, SF. and Hoffmann, M. 2023. Pre-plant application of allyl isothiocyanate controls weeds and pathogens in Eastern North Carolina strawberry (Fragaria x ananassa cv. Camarosa) with and without addition of soil applied steam. HortScience (accepted)
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Progress 09/01/21 to 08/31/22
Outputs
Target Audience:The target audience is strawberry nursery growers and industry partners, especially commercial fumigation companies and grower associations, pest control advisors and industry groups such as the California Strawberry Commission, North American Strawberry Growers Association and participants at the Methyl Bromide Alternative Outreach meeting. Changes/Problems:We did not receive the machines from Norway or South Korea in time to test in 2022. The Konflex steam applicator will arrive too late for the 2022-23 strawberry season so testing of that machine will wait until 2023. What opportunities for training and professional development has the project provided?(1) Graduate Student Training (2 graduate students were trained on the project) (2) Grower education (one field day was conducted). One postdoctoral scientist and one research technician worked on this project, which enhanced their background in field and laboratory research. How have the results been disseminated to communities of interest?Yes the work is being presented at scientific meetings, in publications and at extension meetings. What do you plan to do during the next reporting period to accomplish the goals?A steam applicator from Konflex in The Netherlands is being shipped over this fall and is due to arrive in November 2022. We have invited Soil Steam International from Norway, and JSE from South Korea to bring their new steam applicators for testing in 2023.
Impacts
What was accomplished under these goals?
Work during the reporting period included evaluation of combinations of steam co-applied with additives to improve performance. Work was conducted in strawberry to determine if spot steam application near the planting hole was sufficient to protect the plant. (1) Repeated field trials were conducted in North Carolina (2021-2022) to evaluate the pathogen and weed control efficacy of different steam durations (0-60 min) in combination with Allyl Isothiocyanate. (2) Microplot trials were conducted in North Carolina (2022) to evaluate the pathogen and weed control efficacy of steam in combination with Peroxide and Quicklime. (3) Work was performed at four commercial strawberry fields to determine if spot steam application was sufficient to protect strawberry from soilborne diseases. The objective of this work is to determine if spot steam application near the strawberry planting hole is sufficient to protect strawberry from soilborne diseases. Four studies were initiated in 2022 in coastal California at Oxnard, Salinas and Watsonville. All sites were placed in areas known to have infestations of soilborne strawberry diseases. Each trial used a spot steam applicator with three 25 cm long injectors per hole. The device was set up to treat four planting holes per injection. Each plot had 32 planting holes. Treatments were steam and no steam. Treatments were replicated 6 times and arranged in a randomized complete block. Steam was injected to raise the soil temperatures to 70 to 80C, which was generally accomplished within 60 to 90 seconds. Soil samples were collected before and after steam application and subjected to appropriate lab assays. At Oxnard Fusarium oxysporum was detected and steam reduced this disease by 79%. Steam reduced weed densities by 100% at Oxnard. The Salinas and Watsonville studies will be planted in November 2022 and monitored during the season for disease control and yields.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Fennimore SA, Kim DS, Rachuy RS 2021. Soil Disinfestation with Steam in California Strawberry Nurseries. In: Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions. Online. Proceedings 6.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Volk, E., Fennimore, S., Jennings, K. and Hoffmann, M. 2022. Steam and Allyl Isothiocyanate as soil disinfestation method. Poster Presentation. NC State University Small Fruit Field Day at Horticulture Research Station in Castle Hayne, NC. May 2022
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Volk, E., Fennimore, S., K. Jennings and Hoffmann, M. 2022: Soil Disinfestation with allyl-isothiocyanate followed by steam injection. Oral Presentation, ASHS Annual Conference, Chicago, IL, Jul 30-Aug 4 2022
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Volk, E., Jennings, K., Neal, J. Fennimore, S., and Hoffmann, M. 2022: Controlling Weeds and Pathogens through a Combination of Steam and Allyl-isothiocyanate in North Carolina Strawberry Production. HortScience 57(9), S57.
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Kim DS, Kim SB, Stanghellini M, Meyer-Jertberg M, Fennimore SA Evaluation of a steam application by a mobile applicator for soil disinfestation in strawberry nurseries. HortScience 57:726-730.
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Kim SB, Fennimore SA, Kim DS (2022) A potential relationship between soil disinfestation efficacy and leaf green reflectance. PLOS ONE, 17. DOI: 10.1371/journal.pone.0271677
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Progress 09/01/20 to 08/31/21
Outputs
Target Audience:The target audience is strawberry nursery growers and industry partners, especially commercial fumigation companies and grower associations, pest control advisors and industry groups such as the American Soil Steaming Association, California Strawberry Commission, North American Strawberry Growers Association and participants at the Methyl Bromide Alternative Outreach meeting. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A graduate student worked on the project. Work by this student has helped them gain a better understanding of research and pest management in strawberry. One postdoctoral scientist and one research technician worked on this project, which enhanced their background in field and laboratory research. How have the results been disseminated to communities of interest?We have given four extension talks on this project to strawberry growers and consultants even though contact has been limited due to COVID 19 restrictions. During the project period we held bi-weekly meetings with collaborators, industry partners and strawberry growers to manage the project. What do you plan to do during the next reporting period to accomplish the goals?We have invited Soil Steam International from Norway, and JSE from South Korea to bring their new steam applicators for testing in 2022.
Impacts
What was accomplished under these goals?
Work during the reporting period included evaluation of combinations of steam co-applied with additives to improve performance. Work was conducted at strawberry nurseries to evaluate steam as an alternative to methyl bromide. AITC+ steam. The hypothesis is that the combined activity of steam and Allyl-Isothiocyanate (AITC) will increase pest control efficacy, compared to either of the components on their own. Two strawberry field studies were conducted between Sept. 2020 and May 2021 at Clayton, NC. Each trial was a completely randomize block design with 9 treatments (replicated 4 times): 1) NTC; 2) Pichlor-60 shank applied (170 lb./ac) 3) Steam (60 min, 5 psi); 4) Steam (30 min, 5 psi); 5) Steam (10 min, 5 psi); 6) AITC shank applied (130 lb./acre); 7) AITC (130 lb./acre) + Steam (60 min, 5 psi); 8) AITC (130 lb./acre) + Steam (30 min, 5 psi); 9) AITC (130 lb./acre) + Steam (10 min, 5 psi). Steam was applied through 7 Inch injectors every foot at both sides of the bed. After treatment, soil samples from each replicate were taken at the time of planting and used to assess the presence of pathogens (Pythium spp.) and weeds (weed germination). AITC + Steam controlled Pythium spp. better than steam alone and led to higher fruit yields. Exothermics. The hypothesis is that heat releasing compounds will compliment steam in heating the soil and controlling soil pests. Hydrogen peroxide (H2O2) releases heat when applied to the soil. At Salinas, CA we tested combinations of steam plus 1% w/w H2O2 and saw no significant improvement in control of Pythium spp. or weeds, nor did we observe an increase in soil temperature compared to steam alone. Given the lack of improved efficacy and high cost of 1% w/w H2O2 we recommend no more work on steam co-application treatment. An experiment was conducted at Clayton, NC to determine if steam + exothermics (CaO and Na2O2) will control soil pathogens and weeds better than when the components are used on their own. A microplot trial was conducted in June 2021 to evaluate the weed and pathogen control of steam and steam in combination with exothermic substances in different distances to the injection point. 6 treatments were replicated 4 times each in 1m x .5m plots: 1) non-treated control; 2) steam (30 min, 5 psi); 3) Na2O2 (.1% by soil mass) + water; 4) Na2O2 (.1% by soil mass) + steam (30 min, 5 psi); 5) CaO (1% by soil mass) + water; 6) CaO (1% by soil mass) + steam (30 min, 5 psi). At four distances from the steam injection point, probes with seeds of 3 weed species (Hairy Vetch, Rye Grass, Sida) and Yellow Nutsedge tubers were buried in soil probes in 4 inches depth. Temperatures were monitored and soil samples were taken from the same 4 distances in each replicate. After steaming, soil samples were collected for Pythium spp. assessment at similar distances to injections points. The weed assay showed low germination at the 2.5 cm and 12.5 cm distances in both the CaO + steam and Na2O2 + steam treatments for all assessed weeds and tubers. Pythium spp. levels were lowest at the 2.5 cm and 12.5 cm distances in the Na2O2 + steam treatment, and levels were low at all 4 distances for both the CaO and CaO + steam treatments. Nursery work. The aim of this study was to compare daughter plant production in soils treated with steam vs. the methyl bromide and chloropicrin (MB:Pic) standards. A steam applicator, "Steamy" from Korea was tested at two high-elevation nurseries near MacDoel, CA in Aug. and Sept. 2020. A prototype steam applicator with steam supplied by the Dewpoint hay steamer was also tested at one nursery Aug. 28, 2020. The objective of the steam application was to heat the soil above 60°C for at least 30 min. to a depth of 12 in. The efficacy of the steam application against weeds, Verticillium longisporum, Tylenchulus semipenetrans, and Pythium ultimum were similar to MB:Pic where soil heating is adequate. Nursery Materials and Methods. Steam was applied to a fallow field at two strawberry nurseries near MacDoel, CA. Steamy was a compact diesel-fueled steam applicator. Steam was injected 12 inches using an 80 in. wide set of shanks. The American Challenge applicator used a Dewpoint Hay Steamer and noble plows to inject steam. Soil temperatures were monitored at 4, 8, 10, and 12 inches below the soil surface. Two studies were initiated at Sierra Cascade Nursery (SCN) and Lassen Canyon Nursery (LCN) in 2020. At SCN, 3 treatments replicated 4 times and arranged in a randomized complete block design were established: MB:Pic 57:43 and 2 steam applicators. Steam was applied at SCN using Steamy and the American Challenge applicators August 27-28, 2020. MB:Pic was applied August 31, 2020. Plots were 20 ft. wide by 40 ft. long. Strawberry plants ('EW017') were transplanted on May 11, 2021. At LCN, the treatments included Steamy and MB:Pic replicated 4 times and arranged in a randomized complete block design were established. Steam was applied Aug. 31 to Sept. 2, 2020, and MB:Pic was applied September 12, 2020. Plots were 22 ft. wide by 100 ft. long. The field was fallowed over the winter months. Strawberry plants ('Monterey') were transplanted at LCN April 20, 2021. Weed densities were measured over the entire plot (800 ft2) at SCN and in 500 ft2 section at LCN. Stolon counts were measured in 12 ft. of row at SCN and 5 ft. of row at LCN. Runner counts are the average of 6 subsamples per plot were made at SCN and LCN. Weed densities, weeding times, and numbers of stolons and daughter plants were assessed monthly May to Sept. 2021. Nursery Results and discussion At SCN the Steamy applicator did not raise temperatures to 65° C at any depth. This was likely due to inadequate steam generator capacity for the 20 injection shanks mounted on the machine. When the number of injection shanks was reduced to 12 shanks at LCN, then soil temperatures reached critical temperatures to a depth of 10 inches. The American Challenge treatment reached critical temperatures at 8 and 10 inches but not at 4 or 14 inches. This is likely due to injection of steam at a single depth of about 10 inches. Hand weeding times and weed densities were similar for steam and MB:Pic treatments at both nurseries. At SCN, the American Challenge controlled citrus nematode and V. longisporum similar to MB:Pic. Steamy did not control V. longisporum, at SCN, but greatly reduced citrus nematode viability. At LCN, the Steamy treatment controlled citrus nematode and V. longisporum similar to MB: Pic. At Lassen Canyon Nursery steamy reduced P. ultimum densities by 83%, compared to elimination of this pathogen by MB:Pic. The plant daughter counts and crown diameters at Lassen Canyon Nursery were similar between the Steamy and MB:Pic, but at Sierra Cascade Nursery neither of the steam treatments had as many daughters as MB:Pic. This is likely due to the uneven heating by the American Challenge and inadequate heating by Steamy at Sierra Cascade Nursery. Where adequate steam is applied, results indicate that the soilborne pest control is similar between the steam and MB:Pic treatments. The effect of steam application on pest control has been demonstrated previously in strawberry fruit plantings (Fennimore et al., 2014; Samtani et al., 2012). However, the Steamy machine is inadequate for field scale work in strawberry nurseries it lacks sufficient power, and the shank injectors need to be redesigned. The American Challenge is more promising but needs more design work to ensure even steam distribution throughout the soil profile.
Publications
- Type:
Conference Papers and Presentations
Status:
Awaiting Publication
Year Published:
2021
Citation:
Soil Disinfestation with Steam in California Strawberry Nurseries S. Fennimore, D.S. Kim Methyl Bromide Alternatives Outreach. Preplant Abstract 7.
- Type:
Conference Papers and Presentations
Status:
Submitted
Year Published:
2022
Citation:
Steam Disinfestation of Soil with and without Accelerants. Proc. Northeast. Plant Pest and Soils Conf. 7:(page URL - TBD) Fox, D.E., M. Hoffmann, E. Volk, S. Fennimore, and J. C. Neal.
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