Source: UNIV OF HAWAII submitted to
ORGANIC SWEET POTATO IPM AND SOIL HEALTH MANAGEMENT FOR SMALL- AND MID-SIZE FARMS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
ACTIVE
Funding Source
OTHER GRANTS
Reporting Frequency
Annual
Accession No.
1026778
Grant No.
2021-51300-35225
Cumulative Award Amt.
$740,876.00
Proposal No.
2021-02896
Multistate No.
(N/A)
Project Start Date
Sep 1, 2021
Project End Date
Aug 31, 2025
Grant Year
2021
Program Code
[113.A]- Organic Agriculture Research & Extension Initiative
Project Director
Wang, K.
Recipient Organization
UNIV OF HAWAII
3190 MAILE WAY
HONOLULU,HI 96822
Performing Department
Plant & Environ Protection Sci
Non Technical Summary
The overall goal of this project is to present guidelines for small- to mid-size organic sweetpotato farmers. We aim to develop an economical IPM against sweetpotato weevil, nematodes and soil-borne diseases, while restoring soil health. The project will be conducted in Hawaii and Alabama as this information is especially lacking here but we anticipate the outcomes to have broad applications in other regions. Specific objectives are to: 1) develop organic IPM strategies against sweetpotato weevils using pheromone traps, entomopathogenic nematodes, and Beauveria bassiana through proper spray nozzles; 2) prescribe soil health management strategies compatible with small- and mid-size farms through small-farm equipment, cover crops with allelopathic effects against plant-parasitic nematodes, and fertigation with biological nematicides (ArmourZen®, Majestene®); 3) deduce the relationship between soil microbial profiles associated with the suppression of soil-borne pathogens; 4) estimate the economic return of soil health management and organic IPM approaches for sweetpotato farmers, and 5) broadly transfer knowledge gained through online platforms besides face-to-face extension (decision making apps for phones, new farmers training programs, social media, virtual conferences, college students etc.). A multidisciplinary team of 7 scientists/extension personnel in Hawaii plan to work with at least three commercial organically certified sweetpotato growers in Hawaii and 7 extension agents/specialists/professors from Alabama with expertise in Plant Pathology, Entomology, Horticulture, and Ag Economics. We received strong support from new farmers training programs in Hawaii and Alabama, as well as from the Associate Dean of Research at Auburn University who is initiating an Organic Initiative Demonstration Farm in Alabama.
Animal Health Component
80%
Research Effort Categories
Basic
5%
Applied
80%
Developmental
15%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2151450113034%
1042140112033%
2121450107033%
Knowledge Area
212 - Pathogens and Nematodes Affecting Plants; 215 - Biological Control of Pests Affecting Plants; 104 - Protect Soil from Harmful Effects of Natural Elements;

Subject Of Investigation
1450 - Sweet potato; 2140 - Ground covers;

Field Of Science
1130 - Entomology and acarology; 1120 - Nematology; 1070 - Ecology;
Goals / Objectives
The overall goal of this project is to present a decision support tool for small- to mid-size organic sweetpotato farmers that can lead to an economical integrated pest management against sweetpotato weevil, nematodes and soil-borne diseases, while restoring soil health through cover cropping. We choose to develop this project in Hawaii and Alabama as this information is especially lacking here but anticipate that the concept will be applicable to other regions. It is also our goal to broadly transfer our knowledge gained through online platforms besides face-to-face extension. Specific objectives to achieve this goal are to:1) develop organic IPM strategies against sweet potato weevils using pheromone traps, entomopathogenic nematodes, and Beauveria bassiana through proper spray nozzles;2) prescribe soil health management strategies compatible with small- and mid-size farms through small-farm equipment, cover crops with allelopathic effects against plant-parasitic nematodes, and fertigation with biological nematicides (ArmourZen®, Majestene®);3) deduce the relationship between soil microbial profiles associated with the suppression of soil-borne pathogens;4) Estimate the economic return of various soil health management and organic IPM approaches for sweetpotato farmers; and5) Broadly transfer knowledge gained through online platforms besides face-to-face extension (decision making apps for phone, new farmers training programs, social media, virtual conferences etc.)
Project Methods
Objective 1. Develop organic IPM strategies against SPWObjective 1a (EPN application rates): In Hawaii, a field experiment will be established to determine field inoculation densities for optimal EPN rates once the economic threshold of 4 weevils/pheromone monitoring trap per week is reached on 'Okinawan' sweetpotato using H. indica mix with an organic surfactants such as Oroboost (Oro Agri, USA) using a modified backpack sprayer with drop nozzles of air induction dual pattern (ADPF) flat spray tips. Each treatment will be replicated in 4 plots, arranged in randomized complete block design. Experiment will be repeated once. Sweetpotato weevil (SPW) population will be baited with a ground trap every 2 weeks till harvest. Root damage at harvest from each plot will be evaluated by randomly selecting eight roots and counting the number of feeding pin holes caused by SPW per tuber root. These 8 tubers will be immersed in individual water tubs and quantify the SPW adults or larva emerged after 24 hours. If cadavers are found, they will be incubated on individual White Traps to determine EPN infection rates. Marketable and unmarketable tuber weight will be recorded and weighted. Similar field trials will be conducted at Brewton and Tallassee in Alabama but using commercial EPN, Heterorhabditis bacteriophora (Larvanem®, Koppert Biological System).Objective 1b. Integrating male pheromone traps with EPN and EPF: Field trials will be conducted at Waimanalo and Lihue in Hawaii; Brewton, Tallassee in Alabama and Dobson in North Carolina. Each farm will dedicate 4 distant sweetpotato fields for 1) male lure only; 2) male lure + EPN release; 3) male lure + EPN release + entomopathogenic fungi (EPF) Beauveria bassiana spray, and 4) an untreated control. Pheromone trap will be placed at the beginning and at 4 months after planting, installed in the center of the field using Pherocon unitraps at plant height. SPW will be monitored using ground traps. Infection rates of EPN and EPF will be monitored using the modified White Trap. Sweetpotato damage and yield will be monitored Each location trial will be repeated at least once.Objective 1c. Spray nozzles to increase efficacy of biopesticides: A short experiment will be set up towards harvesting time of a sweetpotato crop where three types of nozzle tips will be compared: 1) Turbo air induction dual pattern (ADPF) flat spray tips, 2) Turbo TeeJet Induction (TTI) nozzle, and 3) most commonly used flat fan nozzle tips. Two biopesticides, Heterorhabditis indica and B. basiana (Mycotol®) will be tested against SPW and for sweet potato yield response.Objective 2. Prescribe soil health management strategies compatible with small- and mid-size farms (conservation tillage, cover cropping and fertigation).Objective 2a. Cover crop Test. Field trials will be conducted in Hawaii and Alabama. The cover crops to be tested include black oat, oil radish, 'Tropic Sun' sunn hemp, '512×14' sorghum-sudangrass hybrid and 'NX-D-61' energy sorghum in a strip-till system using a flail mower and narrow tine tiller. Slips of sweet potato will be planted. Dry biomass of cover crop will be determined. Soil samples will be systematically sampled at the termination of cover crop prior to flail mowing, and at 2-month intervals after sweetpotato planting. Soil properties from each field trial will be examined for extractable P, NO3- nitrogen, soil organic matter, cation exchange capacity (CEC), pH, soil bulk densities and field capacity. In addition, a soil penetrometer will be used as an assessment tool for farmers to monitor soil compaction. Volumetric and gravimetric soil moisture will be recorded at each soil sampling event.Nematodes will be extracted from a 250-cm3 subsample and identified to genus, counted, and subjected to nematode community analysis to calculate trophic group abundance, richness, Simpson's index of diversity, enrichment index (EI), structure index (SI), and channel index (CI).Marketable and unmarketable yield of sweetpotato will be weighed and monitored and recorded for incidence of Java black rot, soft rot, Ceratocystis black rot, nematode damage (root cracking) and sweetpotato weevil damage.Objective 2b. Post plant biological nematicides: Each cover crop main plot in Obj 2a will be split into post-plant fertigation treatments: 1) ArmourZen (Botry-Zen, Ltd.), 2) Majestene (Marrone Bio Innovations) and 3) water control administered at monthly intervals. Plant-parasitic nematodes extracted from each subplot at 2-month intervals will be compared.Objective 3. Deduce the relationship between soil health and soil-borne disease suppression.Soil samples from the root zone of each cover crop established in Objective 2a will be collected at cover crop termination, 28 and 84 days after sweetpotato planting and subjected to phospholipid fatty acid (PLFA) assay (Microbial ID, Inc., Newark, Delaware). PLFA can resolve the microbial community into 6 groups: Gram positive bacteria, Gram negative bacteria, Actinomycetes, Non-AM fungi, AM fungi, and Protozoa and provides their phospholipid fatty acid biomass per nmoleg. Soil microbial respiration will also be estimated using Solvita gel test (Solvita and Woodend Laboratory).Objective 4. Estimate the economic return of various soil health management and organic IPM approaches for sweetpotato farmers.Cost analysis will be conducted at each participating farm individually using a partial budgeting framework method to evaluate costs and benefits of non-chemical based SPW management relative to conventional pesticide based and/or long-term crop rotation practices, as well as the no-treatment control. Our cost analysis will mainly be focusing on the treatment activities and their associated costs which are different from the conventional control. Benefits will be measured in terms of crop yield and quality with their associated prices, plus amount of pesticide use reduction. For costs, data will be collected for numbers of application, labor requirements, and cost of the associated materials. This analysis will estimate the breakeven price, i.e., the maximum amount that growers could pay per unit of the non-chemical IPM methods for results to be comparable to the conventional practices or untreated control. At that price, the grower will be indifferent between using the non-chemical based IPM or the conventional treatment. Since 3 consecutive trials will be conducted at each site, cost analysis changes over time will reflect the progressive benefits of non-chemical based IPM for SPW management.Objective 5. Transfer knowledge through online platforms and face-to-face extension.Detail on online outreach are listed in the Product section. Workshops or videos will be made to educate farmers how to rear EPNs using meal worms in Hawaii. Specific educational workshops / extension publication include:1) DIY EPN rearing techniques and step-by-step EPN inoculation in the field;2) Biological control and spray improvement strategies against sweetpotato weevils;3) Cover cropping for nematodes, soil-borne diseases and soil health management for sweetpotato farmers;4) Cost and Benefits of organic IPM practices for sweetpotato farmers; and5) New Organic Sweetpotato Production Guidelines to increase production of sweetpotato.We will bring awareness to the farmers that SPW is not the only concern for sweetpotato production, so are other pests including plant-parasitic nematodes, rough sweetpotato weevils, sweetpotato whiteflies, Bemisia tabaci, black rot, soft rot and even weeds etc.

Progress 09/01/23 to 08/31/24

Outputs
Target Audience:Sweet potato farmers in Alabama, Hawaii and North Carolina (particularly organic farmers, but some conventional farmers also will seek for non-chemical approach being recommended from our project). New Farmers training programs (e.g. GoFarm Hawaii in 5 locations in Hawaii- Waialua and Waimanalo on Oahu, Hilo on Hawaii Island, Lihue on Kauai Island, Maui). New farmers enrolled in Alabama Beginning Farmer's program Beginning farmers interested to grow sweet potato seeking for effective and reduced risk pest management approaches (many of these farmers in Hawaii are immigrant farmers from Asia including Vietnam, Laos, Thailand, China, and the Philippines). Changes/Problems:It is encouraging to see that when we prepare local isolate of Metarhizium anisopliae into a compost and amended into soil at planting, number of sweet potato weevil larvae recovered from sweet potato at harvest was significantly reduced. This is a breakthrough from our last year report when using EPN or commercial EPF. None-the-less, we hope to further improve organic IPM approaches that can combine soil health enhancement with the use of pheromone baits against SPW, B. bassiana spray along with M. anisopliae compost mix and cover cropping to reduce nematode pest pressure to achieve sweet potato yield improvement. We encounter more serious pest issues (three weevil species and a stem borer) on sweet potato production in Hawaii than we first anticipated (SPW) in Hawaii. In terms of EPN, we have identified more virulent strains of Hawaiian isolates of EPN and hope to improve the effects of EPN in the field. Efforts to formulate these EPNs into desiccated waxworm cadaver is also in progress to improve survival of EPN in the field. While we consistently see the benefits of cover cropping when integrated with various biopesticides used in all three states (AL, HI, NC) for soil health and crop yield improvement, the needs of small-scale sweet potato farmers to use potato harvester attached to a BCS tractor remained a problem to maneuver in the high clay soil in Hawaii. We hope to overcome this soil disturbance from sweet potato harvesting and soil hilling through the use of cover crops with higher biomass production to replenish C lost, e.g. using high biomass cover crops like sunn hemp, sorghum and velvet bean. Performance of biopesticides worked better in the field with better soil health (e.g. in North Carolina field trials) but not well in the field trials conducted in Alabama in our study. This affirm that soil health management needs to go hand in hand with IPM. What opportunities for training and professional development has the project provided?Univ. Hawaii: A total of 2 M.S. students graduated from the University of Hawaii at Manoa working on this project, whereas a Ph.D. student is continuing a longer-term evaluation of soil health. The Ph.D. student won multiple best student awards from the College of Tropical Agriculture and Human Resilience (CTAHR), University of Hawaii while presenting his results. He also secured a new graduate student grant from WSARE to expand on organic sweet potato IPM development. Four undergraduate students were hired to assist with various aspects of this project. An undergraduate student presented this study and won the best student paper at the CTAHR Student Research Symposium, Undergraduate Research Opportunity Program (UROP) at the University of Hawaii, as well as a travel award to attend the Society of Nematologists meeting. A Ph.D. student from Osaka University came to the University of Hawaii as an exchange student and worked on additional organic IPM approaches for sweetpotato with the PI(Total of 8 students). Auburn University: A graduate student has recently graduated from Auburn University. A postdoctoral researcher is being hired to continue the data analysis of this study. Four conference papers were presented at various scientific conferences by the graduate student this year. Two undergraduate students were hired to assist with this project (Total of 3 students and a postdoc). How have the results been disseminated to communities of interest?Univ. Hawaii: In between 2023 Aug to 2024 Aug 2024, a total of 3 in person workshops (2 on Oahu and one on Hawaii islands), one webinar for Kauai sweet potato farmers, and 5 guest lectures for GoFarm Hawaii New Farmers' Trainingprogram (distributed on Oahu, Kauai, Hawaii and Maui islands) were offered by PIs and a graduate student to share our findings from this OREI project besides general cover crop, IPM and soil health management approaches to farmers throughout Hawaii. Auburn University: Between Aug 2023 to Aug 2024, a total of 3 field days were offered to farmers at Smith Research Center and Gulf Coast Research and Extension Center in Alabama, and at Tennessee Valley Research and Extension Center by PI Lawrence and Graham. PI Graham also broadcast an interview with all students and PIs who worked on this OREI project on his The Alabama Crops Report Podcast (https://www.aces.edu/blog/podcast/season-3-episode-11-aloha-from-alabama-extension). PI Wang also highlight this OREI project in 2024 Multistate Research Fund Impacts. https://www.mrfimpacts.org/single-post/sustainable-nematode-management. A total of 11 Conference oral or poster presentations were presented by the students working on this project, and two invited symposia talks were presented by PI Wang and PI Sipes this year. What do you plan to do during the next reporting period to accomplish the goals?We plan to improve organic IPM strategies against SPW based on the research data we gathered so far. We will continue to analyze the data from soil health analysis to depict the relationships between soil health indicators with sweet potato yield and pest suppression. We will evaluate farmers perspective on "Prescription of soil health through cover cropping for organic sweet potato production" Provide partial economic analysis of the Organic IPM approaches for sweet potato production developed in HI and AL. Complete all peer-reviewed publications associated with these projects.

Impacts
What was accomplished under these goals? Obj 1. Develop organic IPM Strategies Entomopathogenic nematode (EPN): Through 5 laboratory trials, susceptibility of sweetpotato weevil (SPW, Cylas formicarius) larvae to 3 indigenous EPN isolated from Hawaii: Steinernema feltiae MG-14, Oscheius tipulae OA-12, and Heterorhabditis indica OM-160 were evaluated. S. feltiae was most promising, causing SPW mortality of 50%, whereas O. tipulae and H. indica caused 30% and 25% SPW mortality, respectively. Subsequently, the efficacy of S. feltiae was tested as basal stem sprayed at monthly intervals beginning at swollen root formation in 2 sweetpotato field trials. However, result was inconclusive due to low pressure of SPW (< 1 weevil/kg root at harvest). Another field experiment was conducted at a commercial sweetpotato farm with high SPW pressure using EPN (O. tipulae). Three treatments tested were 1) O. tipulae monthly basal stem spray (from 2 -5 months after planting), 2) untreated control, and 3) grower carbaryl monthly foliar spray. Although sweetpotato treated with O. tipulae did not reduce SPW damage compared to grower practice, it reduced SPW than the untreated control (P < 0.05). Entomopathogenic Fungi: Two species of entomopathogenic fungi (EPF): Beauveria bassiana (Botanigard®) and a Hawaiian isolate of Metarhizium anisopliae 'KO-002' were evaluated against SPW in the lab and the field. In laboratory petri dish trials, SPW larvae exposed to Botanigard® resulted in 30% larvae mortality. In a series of olfactometer tests, M. anisopliae 'KO-002' did not attract or repel SPW adults. In a greenhouse trial, amending soil with 'KO-002' enhanced sweetpotato growth. In 2 field trials comparing sweet potato plants treated or not treated with Botanigard® as basal stem spray at monthly intervals when sweetpotato swollen roots started to form reduced sweetpotato weevil damage (P ≤ 0.05) but did not reduce SPW population density nor damage level compared to the untreated control (P > 0.05). In another field trial, M. anisopliae 'KO-002' prepared into compost and amended into the soil at planting. Though it did not affect sweetpotato yield or SPW population densities at harvest, it reduced SPW damage (P ≤ 0.05). Thus, it is promising to identify a local isolate of M. anisopliae from Hawaii as commercial biopesticides are highly regulated. Obj. 2. Prescribe soil health management strategies At the University of Hawaii: We examined 4 tropical cover crops with allelopathic effects against reniform (Rotylenchulus reniformis) or root-knot nematodes (Meloidogyne incognita) in greenhouse and field trials. In the greenhouse, we confirmed that velvet bean (VB) was as suppressive to root-knot (M. incognita) and R. reniformis as marigold (MG), sorghum (SG), and sunn hemp (SH), and VB was the only cover crop tested to reduce R. reniform nematode reproductive factor (final nematode counts/initial nematode inoculum) < 1. Four varieties of VB with different characteristics (vine types, bush types, variegated seed coat, plain seed coat) showed equal resistance to M. incognita. Two field trials were conducted to examine the effects of MG, SG, SH, and VB as preplant cover crop vs bare ground followed by 5-months of sweetpotato planting. Velvet bean and SH suppressed reniform nematodes. This research also demonstrated that an integrated pest management strategy combining velvet bean cover cropping with the SPW pheromone trap and the monthly basal stem spray of B. bassiana during the sweetpotato root formation stage provided the most promising organic approach to managing SPW. VB was determined to be a good weed and plant-parasitic nematode suppressive cover crop with great soil health benefits. At Auburn University: A total of 4 field trials were completed, 2 in Alabama and 2 in North Carolina between 2021-2023. A split-plot experiment was conducted in each trial where the main plot was winter cover crop treatments, and the subplot was biopesticides combination vs no biopesticide for management of Meloidogyne incognita and insect pests. At the Alabama field trials, field pea increased M. incognita population densities, but increased sweet potato yield at harvest. In North Carolina, mix cover cropping of wheat, crimson clover, daikon radish, and Elbon rye significantly reduced the number of root-knot nematodes while improving sweet potato yield. The effects of a biopesticide combination (EPN, EPF with Mycotrol, and Majestene as bionematicides) on sweet potato yield were unclear. However, we did observe a trend of soil health effects influencing the performance of biopesticides. Obj 3. Deduce the relationship between soil health and pathogen suppression Univ. Hawaii: Soil physical (water infiltration, aggregate stability, soil moisture), chemical (C and NH4-N) and biological (microbial soil respiration, microbial phospho-lipid amino acid, PLFA, and nematode community indices) were monitored throughout the two field trials conducted in Hawaii. In Trial I, planting velvet bean prior to sweet potato was most promising tropical cover crop because velvet bean: 1) was most water efficient in generating biomass compared to the other 3 cover crops; 2) increased total soil C and soil labile amonia-nitrogen (SLAN) more efficient than the other cover crop within one cropping cycle; 3) fostered a more diverse and less stressful soil community as evidenced by increased soil microbial diversity, gram negative (G-) bacteria, total fungi, arbuscular mycorrhizal fungi (AMF) biomass, and fungi: bacteria ratio, while reducing actinomycete (ACT) microbial biomass; and 4) reduced the proliferation of plant-parasitic nematodes in the soil during the sweet potato growing season; and most importantly, 5) reduced the damage of sweet potato tuberous roots from rough sweet potato weevils and increased the colonization of soil insects by indigenous entomopathogenic fungi such as B. bassiana and M. anisopliae. After repeating the same treatments of cover crops for the second year (Trial II), VB and sorghum (SG) increased G-, AMF, total fungal biomass but only VB increased abundance of bacterivorous nematodes compared to BG (P < 0.05). When all parameters were subjected to Canonical Correspondence Analysis (CCA), different results were observed in Trial I vs II. In Trial I, VB was segregated from BG and all other cover crops in the CCA scatter plot (first two Canonical axes=70.86% variation). Abundance of reniform and root-knot nematodes were negatively related to structure index (SI), indicated a more structured soil food web dominated by omnivorous and predatory nematodes would lead to less plant-parasitic nematodes. However, sweetpotato yield was not affected by all soil health parameters. Progressing to Trial II following soil disruption from sweetpotato harvesting and bed formation, CCA depicted a strong negative relationship between root-knot nematode abundance with channel index (CI), but population densities of reniform nematodes crashed in all treatments and showed no relationship with any soil health parameters. Sweetpotato yield again did not show relationships with any soil health parameters (first 2 canonical axes=81.75% variation). No segregation among treatments at the end of Trial II. We speculate that a suppressive soil against reniform nematodes might have developed after an outbreak of reniform nematodes in Trial I. Auburn University: Soil microbial respiration and microbial biomass were being monitored in all field trials in AL and NC. Progress is being made to depict how changes in soil microbial profile could lead to better performance of biopesticides and lead to better suppression of plant-parasitic nematodes. These results were presented at the Society of Nematologists meeting in Aug 2024. More data analysis will be performed to summarize the results.

Publications

  • Type: Theses/Dissertations Status: Published Year Published: 2023 Citation: Wong, L. 2023. Management of the sweet potato weevil (Cylas formicarius) using pheromone traps, entomopathogenic fungi, and entomopathogenic nematodes. M.S. Thesis, University of Hawaii at Manoa, Honolulu, HI. 154 pp (https://scholarspace.manoa.hawaii.edu/server/api/core/bitstreams/b2e1b3f2-cb44-444d-85e7-bfe78001955e/content).
  • Type: Theses/Dissertations Status: Published Year Published: 2024 Citation: Schloemer, C. 2024. Evaluation of winter cover crops and biological control products to manage Meloidogyne incognita and insect pest damage in organic sweetpotatoes. M.S. Thesis, Auburn University, Auburn, AL. 107 pp (https://etd.auburn.edu/bitstream/handle/10415/9143/Schloemer_Thesis_Final.pdf?sequence=2)
  • Type: Journal Articles Status: Published Year Published: 2024 Citation: Pitiki, M., R. Paudel, J. Mew, and K.-H. Wang. 2024. Examining susceptibility of white clover, buckwheat, black oat and forage radish as a long-term cover crop mix to Meloidogyne incognita. Nematropica 54: 41-48 (https://journals.flvc.org/nematropica/article/view/135613).
  • Type: Journal Articles Status: Submitted Year Published: 2024 Citation: Schloemer, C. M., Graham, Scott H., and Lawrence, Kathy S. Sweetpotato pest challenges and management options. Journal of Integrated Pest Management (Submitted May 2024).
  • Type: Other Status: Published Year Published: 2024 Citation: Wong, L., K.-H. Wang and B.S. Sipes. 2024. Benefits of an entomopathogenic fungus, Metarhizium, for enhancing sweetpotato growth and sweetpotato weevil suppression. H?nai?Ai 54: June 2024. 6 pp. https://gms.ctahr.hawaii.edu/gs/handler/getmedia.ashx?moid=73341&dt=3&g=12.
  • Type: Other Status: Published Year Published: 2023 Citation: Schloemer, C.M. S.H. Graham, K.S. Lawrence. 2023. Greenhouse evaluation of winter cover crops to manage Meloidogyne incognita on sweetpotato, 2023. Plant Disease Management Reports 17: N056. The American Phytopathological Society, St. Paul, MN. https://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2023/N056.pdf
  • Type: Other Status: Published Year Published: 2023 Citation: Schloemer, C.M., S.H. Graham, K.S. Lawrence. 2023. Microplot evaluation of biological control products to manage Meloidogyne incognita on sweetpotato, 2022. Plant Disease Management Reports. Plant Disease Management Reports 17: N055. The American Phytopathological Society, St. Paul, MN. https://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2023/N055.pdf
  • Type: Other Status: Published Year Published: 2023 Citation: Schloemer, C.M., S.H. Graham, K.S. Lawrence. 2023. Efficacy of biological control products to manage Meloidogyne incognita on sweetpotato, 2022. Plant Disease Management Reports. Plant Disease Management Reports 17: N044 (PDMR Volume 17 - Efficacy of biological control products to manage Meloidogyne incognita on sweetpotato, 2022 (plantmanagementnetwork.org)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Wong, L., K.-H Wang, B. S. Sipes. 2024. Organic approaches to manage sweet potato weevil (Cylas formicarius) using entomopathogenic nematodes and entomopathogenic fungi in Hawaii. Society of Nematologists 63rd Annual Conference, Aug 4-9, 2024, Park City, UT.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Larger, K., R. Paudel, B. Wiseman, and K.-H. Wang. 2024. Determining host susceptibility of cover crops to reniform nematodes. Society of Nematologists 63rd Annual Conference, Aug 4-9, 2024, Park City, UT
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Wiseman, B., M. Pitiki and K.-H. Wang. 2024. Model-mania! Exploring differences in soil health management between four tropical cover crops in a sweetpotato agroecosystem. Society of Nematologists 63rd Annual Conference, Aug 4-9, 2024, Park City, UT.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Nicco P. Silvester and B. S. Sipes. 2024. Precision entomopathogenic nematode applications - infected cadavers as an optimized tool for integrated pest management. Society of Nematologists 63rd Annual Conference, Aug 4-9, 2024, Park City, UT.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Schloemer, C., K.S. Lawrence, S.H. Graham, B.S. Sipes, and K.-H. Wang. 2024. Soil health as affected by winter cover crops on sweetpotato yield in Southern U.S. Society of Nematologists 63rd Annual Conference, Aug 4-9, 2024, Park City, UT.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Schloemer, C., K.S. Lawrence, S.H. Graham, Lawaju, B., K.-H. Wang, and B.S. Sipes. 2024. Winter cover crops and biological products to manage Meloidogyne incognita and promote soil health in sweetpotato. Society of Nematologists 63rd Annual Conference, Aug 4-9, 2024, Park City, UT (poster).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Wang, K.-H. 2024. Prescription of soil health for farmers in Hawaii: Perspective from nematodes. In Symposium: Promoting sustainable food systems of the future: Industrial to Indigenous perspectives on regenerative agriculture. American Society of Plant Biology. Honolulu, HI. June 22-26, 2024.
  • Type: Other Status: Published Year Published: 2023 Citation: Schloemer, C., K.S. Lawrence, and S.H. Graham. 2023. Integrated Management of Southern Root-knot Nematode in Sweetpotato. Alabama Cooperative Extension System. Crop Production: ANR-2993. https://www.aces.edu/wp-content/uploads/2023/04/ANR-2993_IntegratedManagementofSouthernRootknotNematodeonSweetpotat_041323aL-G.pdf
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Wiseman, B., Wang, K.-H. 2024. Healthy soil and pest management in organic sweet potato cultivation. ARCS Scholar Symposium, University of Hawaii at Manoa, Honolulu, HI. April 20, 2024.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Wiseman, B., Pitiki, M., Wang, K.H. 2024. Dynamics of plant-parasitic nematode populations in a sweetpotato and cover crop rotation. CTAHR Student Research Symposium, Honolulu, HI. April 11, 2024.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Schloemer, C.M., K.S. Lawrence, S.H. Graham, K.-H. Wang, and B. Sipes. 2023. Winter cover crop, biological control, and Meloidogyne incognita, effects on sweetpotato yield and quality. Beltwide Cotton Conference Vol. 1:608-613. National Cotton Council of America, Memphis, TN. https://www.cotton.org/beltwide/proceedings/2023/event-data/pdf/a127/fl081
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Schloemer, C., S.H. Graham, K.S. Lawrence, K.-H. Wang, and B. S. Sipes. 2024. Can we manage organic sweetpotato pests with winter cover crops and biological control? Entomological Society of America Southern Branch Meeting. March 17-20, 2024, Augusta, GA.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Schloemer, C., S.H. Graham, K-H Wang, B. S. Sipes, and K.S. Lawrence. 2023. Taking it to the field: organic management of Meloidogyne incognita in sweetpotato using winter cover crops and biological control. Auburn University Graduate Poster Showcase, Oct 28, 2023.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Schloemer, Claire, K.S. Lawrence, S.H. Graham, K-H. Wang, B. Sipes. 2023. Taking it to the field: organic management of M. incognita in sweetpotato using winter cover crops and biological control. 53rd ONTA Annual meeting, September 24-29, Caico, Egypt.
  • Type: Other Status: Published Year Published: 2023 Citation: NE2140 Team. 2023. Sustainable Nematode Management. Multistate Research Fund Impacts. https://www.mrfimpacts.org/single-post/sustainable-nematode-management.


Progress 09/01/22 to 08/31/23

Outputs
Target Audience:Sweet potato farmers in Alabama, Hawaii and North Carolina (particularly organic farmers, but some conventional farmers also will seek for non-chemical approach being recommended from our project). New Farmers training programs (e.g. GoFarm Hawaii in 4 locations in Hawaii- Waialua and Waimanalo on Oahu, Hilo on Hawaii Island, Lihue on Kauai Island). New farmers enrolled in Alabama Beginning Farmer's program Beginning farmers interested to grow sweet potato seeking for effective and reduced risk pest management approaches (many of these farmers in Hawaii are immigrant farmers from Asia including Vietnam, Laos, Thailand, China, and the Philippines). General farmers interested to use cover crop for soil health management - these farmers are reaching out to the PI to get advice on "Prescription of Soil Health Management using Cover Crop" (> 40 phone calls or e-mails to the PI during this project period referred from a cover crop seed distributor in Hawaii). Farmers participated in two of our field day/Workshop events: 1) Poamoho Cover Crop Field Day; 2) Sustainable Nematode Management for row crops. Pacific Islander NRCS Conservationists that visited our field site at Poamoho Subscribers of Hanai'Ai, an online newsletter for local farmers in Hawaii Cover crop seed distributors (Kooloa Seed and Supplies, Petcher Seess etc) Oahu Resource Conservation and Development (RC&D) Council, Classroom instruction for an undergraduate program "Sustainable Plant and Soil Health Management (PEPS 410)" - to learn about cover crop for soil health management with lab section in the field to monitor soil health (soil infiltration, microbial respiration, soil compaction, aggregate stability, soil moisture, nematodes as soil health indicators). Experiential learning experience for five graduate students participate in this project to learn about nematode identification, soil health analysis, rearing entomopathogenic nematodes, growing a varieties of cover crops, and sweet potato cultivation. Another 8 undergraduate students were hired to assist in various aspects of data collection from the fields and laboratories. Changes/Problems:Although we see an improvement in marketable yield of sweet potato when combining entomopathogenic nematodes (EPN) and fungi (EPF) application with winter cover cropping in the Alabama and North Carolina trials, there is a lack of efficacy in field application of entomopathogenic nematodes (EPN) against key insect pests of sweet potato in Hawaii. Three weevils and a stem borer were major pests of concern in Hawaii, and our under canopy foliar spray of EPN did not suppress these pests in our 2021-2022 field trial and did not improve crop yield. This is anticipated in part because commercial EPN products were not available in Hawaii, and we had to rely on locally isolated and reared EPNs. We have identified more virulent strains of Hawaiian isolates of EPN and hope to improve the effects of EPN in the field. Efforts to formulate these EPN into desiccated waxworm cadaver is also in progress to improve survival of EPN in the field. While we consistently see the benefits of cover cropping when integrated with various biopesticides used in all three states (AL, HI, NC) for soil health and crop yield improvement, the needs of small-scale sweet potato farmers to use potato harvester attached to a BCS tractor remained a problem to maneuver. This is particularly challenging in high clay soil and no-till plots (without bed formation). We plan to test this harvester again in more sandy soil and form raised beds for sweet potato planting. This will allow us to perform better economic analysis of small-scale sweet potato production in Hawaii. Most sweet potato farmers in AL and NC are mid-size farms and are not challenged by this problem. What opportunities for training and professional development has the project provided?Four graduate students at University of Hawaii (UH), one graduate student at Auburn University (AU), 8 undergraduate assistants (4 from AU and 4 from UH) have been employed or trained to conduct research for this project. The project provides training opportunities for students not limited to the field of Nematology, Entomology, Plant Pathology and Soil Sciences. A total of two society awards were gained by the graduate students presenting at national conferences. Other professional development opportunities provided include new farmers' training programs in Hawaii through GoFarm Hawaii and Alabama Beginning Farmer's program. Guest lectures were presented to new farmers periodically and allowed us to share our findings from this OREI project with the farmers. PI Wang also works closely with conservation planners from Oahu Resource Conservation and Development (RC&D) Council to develop online training materials for Hawaii's Woman Farmers Network. This year we translated a training material about cover crops used into Chinese language to reach out to Chinese immigrant farmers. How have the results been disseminated to communities of interest?Objective 5: Outreach Using this result from velvet bean and the PI's former accumulated data from other tropical cover crops, we generated a chart on "Prescription for Soil Health by Cover Cropping for Hawai'I" (https://gms.ctahr.hawaii.edu/gs/handler/getmedia.ashx?moid=72134&dt=3&g=12 ) and submitted toHanai'Ai Newslettervol 50 for Hawaii agriculture practicians. We migrate ourCover Crop Calculator appto a permanent site to assist farmers in decision making on how much nitrogen fertilizer to cut back from growing cover crops. This is a Cover Crop Calculator to calculate plant available nitrogen from different cover crops based on biomass and N content from an established cover crop. Co-PI Silva had been presenting how to use this app to farmers through various outreach events. Users can access this on their cell phone, an improved version from an excel sheet that one needed to download from our website before. Co-PI, Graham interviewed PIs and students from this OREI project and generated a podcast for the general audience, mostly reaching out to farmers in Alabama. [https://podcasts.apple.com/us/podcast/alabama-crops-report/id1557750157 ] Five guest lectures were delivered to a new farmers' training program, GoFarm during this fiscal year. We reached out to approximately 48 participants (new organic farmers in Hawaii). These guest lectures provided new farmers an overview of cover crop selection for soil health and pest management. We emphasized pest management relevant for small-scale organic sweet potato production. New farmers now have a network to reach out to our PI and co-PIs for specific questions regarding organic sweet potato production. PI Wang and Uyeda along with other members of the Western Cover Crop Council (Hawaii Chapter) identified the top priorities of farmers interested in using cover crops being finding cover crops that are 1) drought tolerant, and 2) nematode resistant/suppressive, 3) can produce seeds locally as imported cover crop seeds some time have short shelf life. What do you plan to do during the next reporting period to accomplish the goals?For Objective 1, we will repeat all the field trials conducted so far. An olfactometer experiment will be conducted to determine if Metarhizium could repel sweet potato weevil. Using the lab studies conducted this year, we will re-explore the use of entomopathogenic nematodes against sweet potato weevils and rough sweet potato weevils in the field. In addition, we will initiate a chemigation trial using bionematicides (MeloCon® LC, Certis Biologicals) against root-knot and reniform nematodes (Objective 2). We will repeat the field trials for Objective 3 (examine the relationship between soil microbial profiles with soil-borne pathogen suppression) and Objective 4 (estimate economic return of soil health management and organic IPM for sweet potato production) in Hawaii and Alabama. More field days and demonstration trials (Objective 5) will be conducted to fulfillreplicated trials for each study.

Impacts
What was accomplished under these goals? Obj. 1. Develop organic IPM strategies University of Hawaii: Three M.S. students examine various biological-based approaches 1) soil application of Entomopathogenic Nematodes (EPN) Steinernema feltiae, 2) release of EPN using lab infected mealworm cadavers (=desiccated EPN bomb), 3) mill run compost colonized by a local isolate of the entomopathogenic fungus, Metarhizium spp., 4) foliar spray of Metarhizium anisopliae (MetMaster), and 5) foliar spray of Beuavaria bassiana (Mycotrol) to manage sweet potato weevil (SPW), Cylas formicarius; West Indian sweet potato weevil, Euscepes postfasciatus; rough sweet potato weevil (RSPW), Blosyrus asellus and sweetpotato stem borer, Omphisa anastomosalis. Experiment I: The field trial at Poamoho Experiment Station examined the integration of preplant cover crops (marigold, sorghum, sunn hemp, and velvet bean vs bare ground), SPW Pherocon unitraps (Alpha Scents), and monthly foliar spray of Mycotrol. The use of SPW pheromone trap and Mycotrol reduced 80% of SPW damaged roots compared to untreated control (P ≤ 0.01). However, most of the harvested sweet potatoes were damaged by rough sweet potato weevil (RSPW). Interestingly, velvet bean (VB) resulted in lowest RSPW damaged roots, a 53.4% reduction compared to the bare ground (BG) (P ≤ 0.05). We monitored occurrence of B. bassiana and Metarhizium anisopliae which are entomopathogens at 1 and 2 months after sweet potato planting. Soil field cages baited with 5 waxworm (Galleria mellonella) larvae were buried 2 inches (5 cm) deep in VB and BG for 1 week, and the incidence of waxworm larvae colonization by B. bassiana (Bb) or M. anisopliae (Ma) were recorded over 2 weeks. Approximately 30% of the waxworms in VB were colonized by Bb or Ma, but no colonization was observed in BG, suggesting that VB enhanced Bb and Ma colonization in the soil. Experiment II: Metarhizium has been reported as an endophyte on several crops and enhances the growth of those plants. Preliminary results were obtained from one greenhouse sweet potato trial and one field trial at Kualoa Ranch. In the greenhouse trial, soil inoculated with an isolate of Metarhizium spp. from the Koolau mountain range increased sweet potato shoot growth by 34.5% after 2 months. In the field trial, the same isolate of Metarhizium, made into a compost mulch by inoculating the Metarhizium cultured on rice into mill run at 2 oz/60 lb, was added to sweet potato raised beds at 0.9 lb/12 ft2 plot. Plant growth at 2 months after planting were measured with noticeable plant height differences between Metarhizium amended and non-amended plots. The experiment is in progress. Experiment III: Following the outcomes from the entomopathogenic nematode (EPN) field trial at TwinBridges Farm reported last year, laboratory trials were being conducted to examine other Hawaiian isolates of EPN and their concentrations against SPW larvae in vitro. Two repeated trials with 10 replications were conducted. Steinernema feltiae MG-14 achieved 90% mortality, whereas Oscheius tipulae OA-12 only caused <40% mortality, compared to approximately 10% mortality of SPW larvae in the no EPN control (P ≤ 0.05). Low dosage of S. feltiae (105 infective juveniles/dish) had similar mortality of SPW larvae as the high dosage (525/dish). Another Hawaiian isolate of EPN, Heterorhabditis indica OM-160 achieved 70% mortality and did not benefit from using higher dosage. Obj. 2. Prescribe soil health management strategies. University of Hawaii: From Experiment I, where cover crops 'NX-D-61' energy sorghum, 'Tropic Sun' sunn hemp, velvet bean, and 'NemaGone' marigold were grown for 3 months, terminated by strip-till before planting sweet potato. Soil samples throughout the crop were subjected to a series of soil physical and chemical property tests, microbial profile assay using phospholipid fatty acid (PLFA) analysis, and nematode community analysis as soil health indicators. VB increased soil C at 2 weeks after strip-tilling of the cover crop compared to the BG. Though not different from the other treatments, VB resulted in the highest water infiltration rate. Based on Solvita Labile Amino-Nitrogen (SLAN) test which reports organic nitrogen reserves present as amino-sugars in soil, VB increased ammonia-N in the soil compared to BG (P ≤ 0.05), indicating a higher pool of plant available organic N. Based on PLFA analysis, VB increased soil microbial diversity, gram-negative bacteria, total fungi, arbuscular mycorrhizal fungi biomass, and fungi: bacteria ratio (F/B) (P ≤ 0.05), but lowered actinomycete biomass (P ≤ 0.05). All of which indicated that VB promoted a more diverse, and less stressful soil conditions. Auburn University Field Trials: An Auburn University graduate student conducted two winter cover crop field trials in Brewton, Alabama (Trial I) and Dobson, North Carolina (Trial II) for a second year. Seven cover crops tested in Brewton were crimson clover, 'Elbon' Rye, Daikon radish, 'Koto' buckwheat, brown mustard, field peas and black oat; whereas 4 cover crops tested in Dobson were Crimson clover, Elbon Rye, Daikon radish, wheat and a mix of Elbon rye, Crimson clover, and Daikon radish. Cover crops were planted and grew from October2022 to May 2023 and sweet potato was planted June 6, 2023 in Alabama and June 9, 2023 in North Carolina. Field peas generated the highest biomass in Trial I and elbon rye generated the highest biomass in Trial II. 30 days after planting (DAP), crimson clover plots supported the highest plant-parasitic nematode population in Trial I. The fallow plots supported the highest plant-parasitic nematode population at 30 DAP in Trial II. Both experiments are ongoing with soil health monitoring. Greenhouse tests: An Auburn University graduate student conducted two greenhouse tests of winter cover crops (Test 1) and summer cover crops (Test 2) on root-knot nematode (Meloidogyne incognita) reproduction. Winter cover crops tested included black oats, crimson clover, daikon radish, elbon rye, field peas, wheat, and yellow mustard. Summer cover crops tested included 'Pipper' sudangrass, sunn hemp, and velvet bean. In Test 1, root-knot nematode numbers were highest on field peas (5430 eggs/g roots) and lowest on 'Elbon' rye (48 eggs/g root) after 56 days. In Test 2, velvet beans supported the lowest population of root-knot nematodes (18 eggs/g roots) followed by sunn hemp and sudangrass. Ob. 3: deduce the relationship between soil health and pathogens suppression Sweet potato harvested from each plot in Experiment I were subjected to postharvest storage observation after curing in a greenhouse for 1 week. Roots were stored in a plastic shoebox in a dark room for 2 months. Although a portion (27/60) of the sweet potatoes had mold growing on the surface of the roots during the storage, only 3 sweet roots remained with mold at the end of the 2-month observation. No difference was observed among treatments (P > 0.5). Thus, we couldn't draw a relationship between soil microbial profiles with soil-borne pathogens on sweet potatoes. When compiling all the PLFA biomass, nematode community indices, soil physical and chemical properties, and yield in B. bassiana treated (Bb+) vs non-treated (Bb-) plots using multivariate analysis, the first 2 axes explained 86.91% of variance. Yield in Bb+ were positively related to nematode structure index, enrichment index, and richness, soil carbon content, volumetric soil moisture, water infiltration rate, arbuscular mycorrhizal fungi biomass and dry biomass of cover crops. Interestingly, yield from Bb- had negative relationships with the above parameters but was positively related to soil aggregate stability. Thus, application of Bb showed synergistic effects when used in conjunction with planting cover crops with high biomass production.

Publications

  • Type: Websites Status: Published Year Published: 2023 Citation: Cover Crop Research https://cms.ctahr.hawaii.edu/wangkh/Research-and-Extension/Cover-Crops
  • Type: Journal Articles Status: Published Year Published: 2023 Citation: Schloemer, C.M., S.H. Graham, K.S. Lawrence. 2023. Efficacy of biological control products to manage Meloidogyne incognita on sweetpotato, 2022. Plant Disease Management Reports 17: N044. The American Phytopathological Society, St. Paul, MN. https://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2023/N044.pdf
  • Type: Other Status: Published Year Published: 2023 Citation: Wang, K.-H., and B. S. Sipes. 2023. Prescription for soil health by cover cropping in Hawaii: for annual cropping systems. HanaiAi 50: June 2023. (https://gms.ctahr.hawaii.edu/gs/handler/getmedia.ashx?moid=72134&dt=3&g=12)
  • Type: Other Status: Published Year Published: 2023 Citation: Schloemer, C.M., S. H. Graham, and K. S. Lawrence. 2023. Integrated management of southern root-knot nematode on sweet potato. Alabama A&M & Auburn University Extension, Alabama Cooperative Extension System. 4 pp. (https://www.aces.edu/blog/topics/crop-production/integrated-management-of-southern-root-knot-nematode-on-sweet-potato/)
  • Type: Other Status: Published Year Published: 2023 Citation: Manandhar, R., Taiwan, G., and Wang, K.-H. 2022. Farmer Driven Sweetpotato Seevil IPM using UNI-Traps. 2023. HanaiAi 48: Newsletter December 2022. 7 pp. https://gms.ctahr.hawaii.edu/gs/handler/getmedia.ashx?moid=71762&dt=3&g=12.
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2023 Citation: Wang, K.-H., Paudel, R., Marquez, J., and Waisen, P. 2023. Nematode linkage to regenerative agriculture in the tropics/subtropics. Symposium How Will Regenerative Agricultural Practices Affect Parasitic Nematode Populations? Society of Nematologists 62nd Annual Conference, July 9-14, 2023, Columbus, Ohio (50 audience).
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2023 Citation: Wiseman, B. 2023. Soil biology- the bounty and burden of soil microbes. 2023 Summer Faculty of Holden Village (https://www.holdenvillage.org/program/2023-faculty/), July 30-Aug 4, 2023, Chelan, WA (25-45 participants).
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2023 Citation: Silvester, N.P. and Sipes, B.S. 2023. Survival and infectivity of entomopathogenic nematodes from desiccated living bombs. Society of Nematologists 62nd Annual Conference, July 9-14, 2023, Columbus, Ohio.
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2023 Citation: Wong, L., Wang, K.-H., and Sipes, B.S. 2023. Mortality of the sweet potato weevil (Cylas formicarius) larvae caused by Steinernema feltiae. Society of Nematologists 62nd Annual Conference, July 9-14, 2023, Columbus, Ohio.
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2023 Citation: Pitiki, M., B. Wiseman, and K. -H. Wang. 2023. Evaluating soil health benefits of four tropical cover crops in the tropic for sweet potato production. Society of Nematologists 62nd Annual Conference, July 9-14, 2023, Columbus, Ohio.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: Schloemer, C., Wang, K.-H., Sipes, B.S., Graham, S.H., and Lawrence, K.S. 2022. Evaluation of sweet potato IPM using organic methods. Joint Annual Meeting of the Entomological Society of America Vancouver, WA (student Second Place award for oral presentation).
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2023 Citation: Schloemer, C., Lawrence, K.S., Graham, S.H., Wang, K.-H., and Sipes, B.S. 2023. Winter cover crops and biological products to manage Meloidogyne incognita and promote soil health in sweetpotato. Society of Nematologists 62nd Annual Conference, July 9-14, 2023, Columbus, Ohio.


Progress 09/01/21 to 08/31/22

Outputs
Target Audience: Sweet potato farmers in Alabama, Hawaii and North Carolina (particularly organic farmers, but some conventional farmers also will seek for non-chemical approach being recommended from our project). New Farmers training programs (e.g. GoFarm Hawaii in 4 locations in Hawaii- Waialua and Waimanalo on Oahu, Hilo on Hawaii Island, Lihue on Kauai Island). New farmers enrolled in Alabama Beginning Farmer's program Beginning farmers interested to grow sweet potato seeking for effective and reduced risk pest management approaches (many of these farmers in Hawaii are immigrant farmers from Asia including Vietnam, Laos, Thailand, China, and the Philippines). General farmers interested to use cover crop for soil health management - these farmers are reaching out to the PI to get advice on "Prescription of Soil Health Management using Cover Crop" (> 30 phone calls or e-mails to the PI during this project period referred from a cover crop seed distributor in Hawaii). Farmers participated in two of our field day events: 1) Poamoho Field Day; 2) Healthy Soil, Healthy Farm Field Day and Workshop at Island Harvest, Kohala. Classroom instruction for an undergraduate program "Sustainable Plant and Soil Health Management (PEPS 410)" - to learn about cover crop for soil health management with lab section in the field to monitor soil health (soil infiltration, microbial respiration, soil compaction, aggregate stability, soil moisture, nematodes as soil health indicators). Experiential learning experience for four graduate students participate in this project to learn about nematode identification, rearing entomopathogenic nematodes, growing a varieties of cover crops, and sweet potato cultivation. Changes/Problems:While Objective 1 is currently facing challenges in field efficacy of entomopathogenic nematodes, we will continue to rear other strains of EPN that are more virulent for field trials in Hawaii. Co-PIs in Alabama would be testing commercial strains of EPN known to be more virulent in the field. It took a long time for PI in Hawaii to purchase a small farm sweet potato harvester, but we anticipated the equipment can be shipped in the next few months. This will allow us to perform better economic analysis of small-scale sweet potato production in Hawaii. What opportunities for training and professional development has the project provided?Three graduate students at University of Hawaii (UH), one graduate student at Aurburn University (AU), 5 undergraduate assistants (4 from AU and 1 from UH), 2 post doctorate researcher in AU (worked on this project for 3 months) and a high school volunteer in Hawaii have been employed or trained to conduct research for this project. The project provides training opportunities for students or post doctorates not limited to the field of Nematology, Entomology, Plant Pathology and Soil Sciences. Other professional development opportunities provided include new farmers' training programs in Hawaii through GoFarm Hawaii and Alabama Beginning Farmer's program. Guest lectures were presented to new farmers periodically and allowing us to share our findings from this OREI project with the farmers. PI Wang also works closely with conservation planners from Oahu Resource Conservation and Development (RC&D) Council to develop online training materials for Hawaii's Woman Farmers Network. How have the results been disseminated to communities of interest?We initiated a "New Sweetpotato Production Guidelines" project starting from preparing a guideline for sweetpotato farmers to manage plant-parasitic nematodes organically. An infographic powerpoint entitled "Nematode Management for Sweetpotato" were shared with our extension agents that work with sweet potato farmers. We transferred a cover crop plant available nitrogen estimation excel sheet into an app for farmers to decide how much nitrogen fertilizer they can cut back from growing cover crops. Using this model, we will continue to develop more cover crop decision making tools / apps later. Five guest lectures were delivered to a new farmers' training program, GoFarm. We had reached out to approximately 48 participants (new organic farmers in Hawaii). These guest lectures provided new farmers an overview of cover crop selection for soil health and pest management. We emphasized on pest management relevant for small-scale organic sweet potato production. New farmers now have a network to reach out to our PI and co-PIs for specific questions regarding organic sweet potato production. PI Wang and Uyeda along with other members of the Western Cover Crop Council (Hawaii Chapter) identified the top priorities of farmers interested in using cover crops being: finding cover crops that are 1) drought tolerant, and 2) nematode resistant/suppressive, 3) can produce seeds locally as imported cover crop seeds some time have short shelf life. A post-presentation survey form from our soil health outreach activities in Summer 2022 revealed that 1) all participating farmers are very interested in growing cover crop using minimal-tillage; 2) 90% of these farmers are interested in growing short-term instead of long-term cover crops; and 3) 55% grow cover crops for soil health, and 18% for soil-borne pathogens management. What do you plan to do during the next reporting period to accomplish the goals?For Objective 1, we will explore the use of other indigenous populations of entomopathogenic nematodes and fungi against sweet potato weevils and rough sweet potato weevils. In addition, we will initiate a chemigation trial using bionematicides (ArmourZen®, Majestene®) against root-knot and reniform nematodes (Objective 2). We will initiate field trials for Objective 3 (examine the relationship between soil microbial profiles with soil-borne pathogen suppression) and Objective 4 (estimate economic return of soil health management and organic IPM) in Hawaii and Alabama. More outreach (Objective 5) will be conducted in Alabama once we completed the two cover crop field trials on-going in Alabama and North Carolina. Recently we initiated a post presentation survey for farmers to reach out to us for the "Prescription for soil health Using Cover Crop" program. We ask the farmers to describe soil health issues they are challenged with in their farms. We will then mail them a cover crop mix for a trial area.

Impacts
What was accomplished under these goals? Objective 1. Develop organic IPM strategies against sweetpotato weevils University of Hawaii: A field trial was conducted by a M.S. student at a commercial sweetpotato farm, Waialua, HI to evaluate efficacy of three organic approaches to manage sweetpotato weevils (SPW) on 'Okinawan' sweetpotato at Waialua on Oahu, HI. A 2×2×2 (pheromone × EPN × Beauveria) factorial designed experiment was conducted. A standard practiced (pesticide spray) was also included for comparison. Half of the field was within the efficacy zone of a Pherocon Unitrap baited with 1000 g male lure (Z3-Dodecenyl-E2-butenoate, Alpha Scents, Inc., West Linn, OR), the other half was not. Half of these plots received an indigenous entomopathogenic nematode (EPN) as foliar treatment (185,325 infective juveniles)/ha, whereas half of them were not. For the Beauveria treatment, half of these plots received Mycotrol ESO® (Beauveria bassiana, Bioworks) at 4 fl oz/acre delivered through 20 gal/acre of water. Both EPN and Beauveria treatments were added with an organic surfactant, Kinetic® and applied above and below the leaf canopy. Unfortunately, due to culture failure of Sterinernema feltiae in the laboratory, a weaker EPN strain, Osheius tipulae, was used as foliar EPN spray in this trial, with no effect against SPW. A laboratory petri dish experiment confirmed that SPW larvae were more susceptible to S. feltiae than O. tipulae. Rough sweetpotato weevil (Blosyrus asellus) was a more dominant pest in this field than SPW and resulted in severe damage to sweet potato roots at harvest, but the larva as well as the adults of this pest remain cryptic and hard to monitor. It is speculated that Unitrap effective zone is wider than the 60 m diameter zone as suggested by the product label, as high number of SPW adults were captured in the Unitrap and overall low recovery of sweetpotato roots with SPW damage and larva in the roots sampled (< 3 per 100 g roots) regardless of close to or far from the Unitrap. None-the-less, Unitrap reduced damage scale (scale of 0-5) of combining of SPW and rough SPW but failed to increase sweet potato yield at 4 months after planting. Mycotrol® could not reduce the damage rating of SPW or rough SPW, in fact it significantly increased SPW larvae in the roots (P ≤ 0.05). Regardless of poor performance of Mycotrol and EPN foliar treatments, we were able to reisolate an indigenous EPN (putatively identified as a Heterorhabditis sp. based on18s rDNA ITS) and a fungal isolate with colony growth similar to Beauveria. Pathogenicity tests of these isolates against SPW larva or rough SPW larva remained to be tested to be relevant. Among the three approaches of IPM management tested against SPW (EPN, Beauvaria, Pheromone trap), growers are most excited about the use of Pherocon Unitrap. A total of 16 Unitraps purchased from this project had been distributed to commercial and new sweet potato farmers in Hawaii. Most of these farmers were not previously aware of using pest specific pheromone traps to control SPW. These farmers now are less worried about SPW but are asking for more organic approaches to manage rough sweetpotato weevils organically. Objective 2. Prescribe soil health management strategies A graduate student at Auburn University conducted two cover crop field trials in Brewton, Alabama (Trial I) and Dobson, North Carolina (Trial II). Seven cover crops tested in Brewton were Crimson clover, Elbon Rye, Daikon radish, Koto buckwheat, brown mustard, field peas and black oat; whereas 4 cover crops tested in Dobson were Crimson clover, Elbon Rye, Daikon radish, wheat and a mix of Elbon rye, Crimson clover, and Daikon radish. Cover crops were planted from Nov 2021 to May 2022. Sweet potato was planted Jun 15, 2022. Elbony rye generated the highest biomass at 5 months after planting, whereas Koto buckwheat and brown mustards did not survive the winter. In both locations, plant-parasitic nematodes were present at similar population levels across all cover crops at sweet potato planting and at 30 days after planting (DAP). Beneficial nematode (mostly bacterial feeders) populations were significantly higher following the Crimson clover, Elbon rye and wheat cover crops compared to the Daikon Radish. In Alabama and North Carolina, the sweet potato plots were split and untreated or treated with the biological nematicide, Majestine®. Majestine increased the Normalized Difference Vegetation Index (NDVI) green rating for the sweet potato crop following the Elbon Rye. Soil health is being monitored using nematode community and microbial biomass (phospholipid fatty acid) analysis. Objective 5: Outreach (see section onHow have the results been disseminated to communities of interest).

Publications

  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: Wong, L., K.-H. Wang, and B. S. Sipes. 2022. Infection and mortality of sweetpotato weevil (Cylas formicarius) by Hawaiian isolates of entomopathogenic nematodes, Steinernema feltiae and Oscheius sp. Society of Nematologists 61th Annual Conference, September 26-29, 2022, Anchorage, Alaska.
  • Type: Other Status: Published Year Published: 2022 Citation: Manandhar, R. 2022. Three promising sweet potato varieties for Kaua?i from a 2019 trial. CTHAR Cooperative Extension V46: 7 pp. (https://gms.ctahr.hawaii.edu/gs/handler/getmedia.ashx?moid =71115&dt=3&g=12).