Integrating the Farmer into Pest Management Innovation for Sweetpotatoes.

Objective 1: Demonstrate sweetpotato pest management using sustainable techniques including velvet bean preplant cover crop and entomopathogenic fungus.  

     Trials were started at five farms: Pua Nani Farm, Oahu; Island Produce, Oahu; Wauke Shores, Kauai; Hawaii Sunrise Sweetpotatoes, Hawaii Island; and Kapi’olani Farm, Oahu.  Farms are referred to by pseudonyms per the human-subjects research plan. At each farm, the pest management practices were trialed in three repeated plots and compared against three control plots grown according to the farmers’ current practices.  Plot sizes were a minimum of 5 feet by 15 feet.  Plots were planted with a cover crop for two to three months followed by sweetpotatoes of the variety preferred by the farmer.  Sweetpotatoes were planned to grow for 4-6 months depending on the variety and conditions.  Pest management practices were trialed during the study including velvet bean preplant cover crop for management of plant-parasitic nematodes, entomopathogenic fungus for control of sweetpotato weevil, and a pheromone trap for monitoring sweetpotato weevil population.  The entomopathogenic fungus Metarhizium species ‘Koo-002’ (an isolate from Hawai‘i) was not trialed as planned due to concerns about pesticide regulations for the biopesticide.   

     As of May 31, 2025, the farms were in different stages of the trial.   Pua Nani Farm, Island Fruits, Wauke Shores, and Hawaii Sunrise Sweet Potatoes completed the cover crop phase and were growing sweetpotatoes.  Kapi’olani Farm was approximately one month in to the cover crop phase. 

Velvet bean trial: At each farm, three trial plots were planted with velvet bean at a rate of 30 pounds of seeds per acre.  After two to three months, the velvet bean was terminated and incorporated into the soil.  The velvet bean plots were compared to three trial plots planted with buckwheat, a comparison cover crop chosen by the participants.

Sweetpotato weevil monitoring with pheromone trap: The abundance of sweetpotato weevils was monitored by the farmer on a biweekly basis using an UNI-trap with a pheromone lure for sweetpotato weevil (active ingredient (Z)-3-Dodecenyl-(E)-2-butenoate, Alpha Scents, Canby, OR). When the sweetpotato weevil abundance surpassed the threshold for insecticide treatment, we recommended treatment with a suspension of Mycotrol bioinsecticide containing Beauveria bassiana Strain GHA entomopathogenic fungus (Lam International Corporation, Butte, MT).  The treatment threshold was decided with the participant farmers because previously proposed thresholds are highly disparate: 4 weevils/trap/week (Jansson, 1991) and 50 weevils/trap/week (Manandhar et el., 2022).  As of May 31, 2025, the number of weevils caught in the traps was not observed with sufficient accuracy to be used to compare the treatment and control plots. 

Entomopathogenic fungus trial and assay: After termination of velvet bean and prior to planting sweetpotatoes, the plots were not treated with Metarhizium sp. ‘Koo-002’ inoculated in mill run at a rate of 1,305 pounds per acre as planned due to concerns about pesticide regulations for the local Metarhizium strain.  During the growing season Mycotrol bioinsecticide containing Beauveria bassiana entomopathogenic fungus was periodically applied at the base of the sweetpotatoes, with timing dependent on the abundance of weevils captured in the pheromone traps. The entomopathogenic fungi prevalence in the soil will be monitored at the middle and end of the sweetpotato crop.  The entomopathogenic fungi assay will be conducted using protocol modified from McCoy et al. (2007) in which five mealworms as sentinel species are placed in a mesh cage filled three-quarters full of field soil, placed fifteen centimeters under the surface of the soil for one week, and then removed and placed in a petri dish where fungal growth can be observed.  The mesh cages will be made from 177-µm screen strainers (Kleen-rite corp., Columbia, PA) sealed with FalconTM tubes lids (ThermoFisher Scientific Inc., Waltham MA).  The number of waxworms that die from fungal colonization will be used to determine the prevalence of entomopathogenic fungus in the field.

Nematode and quick soil health assay: The prevalence of soil dwelling nematodes was recorded in both the control and trial plots before and after planting the cover crop and will be recorded at the mid-season and end-season of the sweetpotato crop. In each plot, a single composite soil sample was collected consisting of an aggregate of six cores from the top ten centimeters of soil.  For each composite sample, nematodes were extracted from a 250 cm³ subsample by elutriation and centrifugal flotation (Bryd et al., 1976; Jenkins, 1964). The extracted nematodes were identified and counted under an inverted microscope. The same soil samples were also subjected to quick soil health assays using Solvita kits such as Solvita Burst (microbial respiration), VAST (aggregate stability), and SLAN (labile ammonia nitrogen; Woods End Laboratories Inc., Mount Vernon, ME).

Analysis of sweetpotato damage: Depending on the variety of sweetpotato selected by the farmer, the sweetpotatoes will be ready for harvest four to six months after planting.   Harvested sweetpotatoes will be graded based on standards from the Hawaii Department of Agriculture (Marketing and Consumer Services Division, Commodities Branch, 1986), and total yield in weight and count will be recorded for each grade. Unmarketable roots will be categorized by the type of damage caused by different pests.  

Statistical Analysis: The trial plots at each farm will be compared with the control plots using one-way analysis of variation with three replications.

Objective 2: Identify the values and priorities that impact farmers’ decision making and judgment during the adoption of new sustainable pest control techniques (Wiseman and Le).

     The values and priorities of the five participating farmers were explored through the following qualitative techniques during the field trial of velvet bean cover crop and entomopathogenic fungi as pest management techniques for sweetpotatoes.  Outcomes of all the qualitative procedures will be compared through triangulation to identify major themes. 

Procedures: 

Semi-structured in-person interviews:  Interviews took place in person at a location near the farming site as agreed upon with the farmer.  Over the course of sixty minutes, a researcher asked the farmer a set of standard questions and additional probing questions based on the responses to the standard questions.  One semi-structured interview was completed at the beginning of the trial, and another will be completed at the end of the trial.

     Preliminary interview standard questions:

• Demographic questions: What is your role on the farm? How many acres do you manage? How many years have you managed the farm?
• How do you decide what to grow on your farm?
• What is your experience growing sweetpotatoes?
• How do you describe the pest damage you have seen on sweetpotatoes?
• If you do not typically grow sweetpotatoes, what prevents you from growing sweetpotatoes?
• When you plant sweetpotatoes, what are your expectations for the crop?
• What sort of pest control do you use on your farm? Why?
• Do you have any specific pest management practices for sweetpotatoes? Why is this your preferred practice?
• When you have a pest problem on your farm, where do you go for help?

     End of season standard questions:

• What was it like using velvet bean and entomopathogenic fungi for pest control?
• Describe the effect that velvet bean and entomopathogenic fungi had on pest control.
• Describe the effect that velvet bean and entomopathogenic fungi had on soil health.
• What was the effect of the sweetpotato weevil pheromone trap on your pest control?
• Describe the equipment you need to adopt these pest control techniques. How can you access this equipment?
• Do you think that you will use either velvet bean or entomopathogenic fungi on your farm in the future? What challenges do you foresee?
• What would prevent you from using these techniques on your farm in the future?
• Who else do you think may be interested in these techniques? Did you share about the techniques with anyone you know?
• What did we learn in this trial?

     Probing questions (examples, for both preliminary and end of season):

• Why do you think that happened?
• What is the connection between ___ and ___ ?
• How did you know when …?
• What led you to make that decision?
• What did you see when that was happening?
• How did you decide…?
• What values or principles guide your decision making? 

     Interviews were recorded and transcribed, except if the participant did not want to be recorded in which case notes were taken during the interview and immediately transcribed following the interview.  The transcriptions will be coded by two researchers. Coded transcriptions will be analyzed for themes.  The content and themes will be compared between the different participants (Creswell & Guetterman, 2019).

Photovoice: Photovoice is a participatory action research method (Liebenberg, 2018). Participants were asked to take three pictures depicting an element of pest management.  After the participant takes the pictures, the researcher and participant will meet to discuss the pictures.  The participant will be asked questions about the picture (listed below) and additional clarifying and probing questions.  The study uses photovoice to elicit the participants’ perspective on pest management and explore priorities and values that the participant holds about pest management. 

     Photovoice questions:

• What do you see in the picture?
• How does this picture relate to our lives?
• Why is this picture important; what does it say?
• What does this picture show to people who are unfamiliar with your farm?

Qualitative field notes: Qualitative field notes describe the context of the study and reflection by the researcher about the positionality of the researcher (Phillippi & Lauderdale, 2018).  Written field notes were recorded immediately after significant research activities such as interviews or field visits to document how the study is unfolding and researcher reflections.  Field notes will be integrated with other data during analysis to provide context for the research. 

Farm Log: The farmer was asked to keep a written log of their activities with the trial plot.  The log included a description of what the farmer did, and their justification for making that decision.  The farm log was not required if the farmer was not comfortable or able to complete the log. 

Member-checking: Following data collection and initial data analysis, member-checking with participants will be used to validate findings.  Member-checking is a validating technique for qualitative research in which the study outcomes are returned to the participants for the participants to comment, reflect, and add their interpretation (Birt, 2016).  

Timeline of research events for Objective 2:

1. Initial interview and farm plan. The initial interview focused on the farmer priorities, values, and farm operation. Following the interview, the researcher and farmer planned the project logistics.  Initial interviews were completed for all farms.
2. Farm visits. During routine farm visits throughout the growing season, the researcher collected field notes that detail both agronomic observations (crop growth, pest prevalence) and described interactions with the farmer.  Farm visits are in progress for all farms.
3. Photo voice. The photovoice participatory action research activity will take place in the middle of the season.  The activity has been introduced to four of the five participating farmers.
4. End of season interview. The end of season interview will focus on farmers’ perception of the pest control techniques, how well they adhered to the plan, what challenges they faced during the growing season, how they talked about the trial with their peers, and other topics.
5. Debriefing session and member-checking. After initial analysis of the data is complete, the outcomes of the study will be shared with participants and their feedback will be solicited through member-checking. 

Objective 3: Identify key practices and/or major obstacles for using velvet bean preplant cover crop and indigenous Metarhizium on the farm for control of sweetpotato weevils.

Insight from the qualitative inquiry of farmer values and priorities in pest management will be cross-examined with the quantitative results from the field trials of pest management techniques to identify best practices and major obstacles for using the sustainable pest management techniques in this study.  This objective follows the convergent parallel design model of mixed methods study in which qualitative and quantitative data are collected and then related to each other for interpretation (Schoonenboom & Johnson, 2017).   Through triangulation of the qualitative and quantitative data, areas of convergence and divergence between the results will be noted; for example, was there any place where the technique had a favorable perception despite its poor performance.   

Integration of the qualitative and quantitative data will be carried out by researchers following analysis of the qualitative and quantitative data.  Participants will have the opportunity to contribute to integration during the member-checking and debriefing meeting at the end of the study.   

Outputs of the mixed-methods integrated analysis will shed light on key practices that support adoption of the pest control techniques keeping in mind both technical aspects of the pest management technique and practical or sociological elements of the farmers decision making.  These outcomes will be used to craft an extension bulletin presenting these pest control techniques to a larger audience.

Timeline

References

• Birt, L., Scott, S., Cavers, D., Campbell, C., & Walter, F. (2016). Member Checking: A Tool to Enhance Trustworthiness or Merely a Nod to Validation? Qualitative Health Research, 26(13), 1802–1811. https://doi.org/10.1177/1049732316654870
• Byrd, D. W., Barker, K. R., Ferris, H., Nusbaum, C. J., Griffin, W. E., Small, R. H., & Stone, C. A. (1976). Two Semi-automatic Elutriators for Extracting Nematodes and Certain Fungi from Soil. Journal of Nematology, 8(3), 206–212.
• Creswell, J. W., & Guetterman, T. C. (2019). Analyzing and Interpreting Qualitative Data. In Educational Research: Planning, Conducting, and Evaluating Quantitative and Qualitative Research (6th ed., pp. 236–265). Pearson Education, Inc.
• Jansson, R. K., L. J. Maon, and R. R. Heath. 1991. Use of sex pheromone for monitoring and managing Cylas formicarius, pp. 97-138. in R. K. Jansson and K. V. Raman (eds.) Sweet Potato Pest Management: A Global Perspective. Westview Press, Inc., Boulder, Colorado, p. 458.
• Jenkins, W. R. (1964). A rapid centrifugal-flotation technique for separating nematodes from soil. Plant Disease Reporter, 48(692).
• Liebenberg, L. (2018). Thinking critically about photovoice: Achieving empowerment and social change. In International Journal of Qualitative Methods (Vol. 17, Issue 1). SAGE Publications Inc. https://doi.org/10.1177/1609406918757631
• McCoy, C. W., Stuart, R. J., Duncan, L. W., & Shapiro-Ilan, D. I. (2007). Application and evaluation of entomopathogens for citrus pest control. In Field manual of techniques in invertebrate pathology (pp. 567–581).
• Phillippi, J., & Lauderdale, J. (2018). A Guide to Field Notes for Qualitative Research: Context and Conversation. Qualitative Health Research, 28(3), 381–388. https://doi.org/10.1177/1049732317697102
• Schoonenboom, J., & Johnson, R. B. (2017). How to construct a mixed methods research design. Kolner Zeitschrift Fur Soziologie Und Sozialpsychologie, 69, 107–131. https://doi.org/10.1007/s11577-017-0454-1