Control of Bacterial Wilt Disease of Ginger through an Integrated Pest Management Program

Final Report for SW10-013

Project Type: Research and Education
Funds awarded in 2010: $289,245.00
Projected End Date: 12/31/2014
Region: Western
State: California
Principal Investigator:
Dr. Susan Miyasaka
University of Hawaii
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Project Information

Abstract:

The overall goal of this project is to develop and demonstrate sustainable farming practices that control bacterial wilt in edible ginger. We have: a) grown and distributed over 1,300 pounds of bacterial wilt-free ginger seed pieces to commercial and backyard growers; b) completed our ginger wilt website that has been accessed over 3,800 times from 66 countries; c) developed a method to test for presence of Ralstonia solanacearum in soil that has been adopted by the Agricultural Diagnostic Service Center; and d) helped to develop bacterial wilt-free seed ginger as a new, high valued product.

Project Objectives:

The overall goal of this project is to develop and demonstrate sustainable farming practices that control bacterial wilt in edible ginger.

Specific objectives were to:

1) demonstrate the importance of clean planting materials;
2) demonstrate procedures to test fields for Ralstonia solanacearum;
3) conduct field studies to determine the effectiveness of green manure crops or rotational crops for pathogen control;
4) conduct greenhouse studies to determine the effectiveness of vermicomposts to control R. solanacearum;
5) conduct economic analysis of sustainable, farming practices; and
6) disseminate information and enhance farmer adoption of practices through a video and a web site.

Introduction:

Edible ginger (Zingiber officinale) is a major export crop in Hawaii grown primarily on Hawaii Island. Bacterial wilt caused by Ralstonia solanacearum is the crop’s most problematic disease. During 1992-93, an epidemic of this disease caused losses of ginger yield of more than 60% of the total crop or 9 million pounds, resulting in a farm gate value loss of $5 million. Similar losses occurred in 1994-95 and continue today. Edible ginger production in Hawaii has declined drastically, from its peak farm gate value of $8.1 million in 2001 to $3.01 million in 2006. Two major factors that contribute to a ginger wilt epidemic are: a) unintentional use of infected planting material; and b) planting in pathogen-infested fields.

Cooperators

Click linked name(s) to expand
  • Dr. Norman Arancon
  • Dr. Linda Cox
  • Hugh Johnson
  • Dr. Bernard Kratky
  • Dr. Scot Nelson
  • Dean Pinner
  • Dr. Michael Shintaku
  • Bill Tocantins
  • Cyrus Wagatsuma

Research

Materials and methods:

Objective 1. Demonstrate the importance of clean planting materials.

Edible ginger plants were tissue-cultured to remove R. solanacearum, then grown in pots, selected for large-sized rhizomes, and multiplied in hydroponic culture for distribution to cooperating growers. Experiments to optimize growing conditions for hydroponic culture of ginger were conducted for the effects of shading and silicon. Each year, a meeting was held for growers to inform them of the importance of planting bacterial wilt-free ginger planting materials and to distribute bacterial wilt-free ginger rhizomes.

Objective 2. Demonstrate procedures to test fields for Ralstonia solanacearum.

Polymerase Chain Reaction (PCR) has been utilized as a sensitive detection technique for many pathogens. Until recently, detection of pathogens in soil has been problematic because of soil compounds that inhibit the PCR reaction. We developed and tested an Enrichment-PCR method that includes a crude soil extraction followed by enrichment in selective media and PCR. This method reveals the presence, as well as viability, of the pathogen.

Objective 3. Conduct field studies.

To demonstrate the importance of planting bacterial wilt-free ginger seed pieces into bacterial wilt-free fields, a commercial grower agreed to cooperate in on-farm field trials. Prior to planting, the fields were tested for presence of R. solanacearum using the Enrichment-PCR method and the pathogen was not found. Bacterial wilt-free seed pieces of ginger were planted in Pepeekeo on the Island of Hawaii during April 2011 and harvested during January 2012. Four replicated rows (20 feet long x 5 foot wide) were planted side-by-side with two border rows. A second field trial in Pepeekeo, Hawaii was conducted in which bacterial wilt-free ginger seed pieces were planted on April 16, 2012 and rhizomes were harvested on February 11, 2013. A similar experimental design followed, as used for the first field trial.

Isolation and testing of antagonistic bacteria. Bacillus sp., particularly B. subtilis, has been reported to provide disease-protective effects for plants. Spore-forming Bacillus spp. were isolated from soil of a healthy ginger field by adding 0.1 g rhizosphere soil to 1 mL of water, vortexed briefly, and heated to 50C for 30 minutes. A small sample of the resulting supernatant was then spread on cycloheximide-containing LB plates. Colonies of two distinct types emerged; one yellow and fluid, the other white and somewhat waxy. 16S ribosomal sequences from each colony type were sequenced and identified as belonging to Bacillus sp. with the white-type cultures B. megaterium. Morphological characteristics of these isolates are consistent with this identification.

Isolation and testing of antagonistic bacteriophages.

Plaque assays were used to detect lytic phages able to infect R. solanacearum. Field soil was mixed with distilled water (1g/10 mL), vortexed for 90 seconds at maximum speed, centrifuged for 10 minutes at 3500 RPM, and passed through a 0.22 um filter before addition to the still-liquid Rs agar suspension at various dilution rates. The soft agar overlay consisted of 50 ul of a stationary phase CPG broth culture of R. solanacearum. For phage propagation, clear round plaques and a small amount of accompanying border region were removed and placed on bacterial overlays on subsequent plates.

Objective 4. Conduct greenhouse studies to determine the effectiveness of vermicomposts.

First pot study.

Dr. Arancon and graduate student Paul Flessner conducted the first pot study starting May 23, 2011 and harvested on  October 30, 2011. Ginger propagules (approximately 2-4 ounces or 50 – 100 g) were sown directly into one gallon pots containing medium amended at different rates with vermicomposts produced by Perionyx excavatus from food wastes and shredded paper [0 (control), 20, 40, 60, 80, 100 percent substitution rates]. Potting medium (Promix BX) and vermicompost were tested for R. solanacearum. Half the pots were inoculated with 108 CFU of R. solanacearum race 4 in 5 ml of water. All 12 treatments (six vermicompost rates x two pathogen rates) were replicated five times and laid out in a randomized complete block design. Plant height and disease symptoms were recorded weekly throughout the growing period. Rhizome yield and quality were recorded at harvest. Presence of R. solanacearum was assessed using the Enrichment-PCR method using race 4 specific primers. Rhizome yield was analyzed with ANOVA using Minitab 16.1.

Second pot study.

Dr. Arancon and student Mr. Ronald Santos conducted a second pot study starting April 24, 2013. Ginger propagules (approximately 50 – 100 g) were sown directly into three gallon pots containing medium amended at different rates with vermicomposts produced by Eisenia fetida from food wastes and shredded paper [0 (control), 1, 5, 10, 20 percent substitution rates]. The rates varied from the previous experiment on the basis of their yield data. Ginger grown in pots substituted with 10 and 20% vermicompost produced the greatest yield significantly. The potting medium (Promix No. 3) and vermicompost were tested for Ralstonia. All pots were fertilized with inorganic and slow release fertilizer (equal parts v:v of Nutricote 13-13-13, 16-40-0, 1-3-38, and 12-0-0). Half the pots were inoculated with 109 CFU of R. solanacearum race 4 in 5 ml of water. All 10 treatments (five vermicompost rates x two pathogen rates) were replicated five times and laid out in a randomized complete block design. All plants were grown in a greenhouse using a controlled drip irrigation system to maintain moisture levels at field capacity. Plant height and disease symptoms were recorded weekly. Symptoms of bacterial wilt were assessed visually using a scale of 0 (no symptoms) to 5 (100% of plant foliage showing symptoms).

Third pot study.

Dr. Arancon and student assistant Johnathan Shestokes conducted a third pot study starting on January 5, 2014. This study was conducted to determine the survivability of R. solanacearum inoculated into vermicompost-treated medium. An emphasis was placed on the presence of pathogens in the soil instead of plant symptoms. Ginger propagules (approximately 50 – 100 g) were sown directly into three gallon pots containing medium amended at different rates with vermicomposts produced by Eisenia fetida from food wastes and shredded paper [0 (control), 5, 10, 20, 40 percent substitution rates]. Potting medium (Promix No. 3) and vermicompost were tested for Ralstonia. All pots were fertilized with inorganic, slow release fertilizer (equal parts v:v of Nutricote 13-13-13, 16-40-0, 1-3-38, and 12-0-0). All the pots were inoculated with 107 CFU of R. solanacearum race 4 in 20 ml of water on May 24, 2014. All five treatments (five vermicompost rates) were replicated five times and laid out in a randomized complete block design. All pots were raised in a greenhouse with a controlled drip irrigation system to maintain moisture levels at field capacity at all times. Symptoms of R. solanacearum were assessed visually as described earlier.

Core samples were collected from each pot on June  2, 2014 for Enrichment PCR (Motomura, 2013) and gel electrophoresis to detect the presence of R. solanacearum race 4. Aliquots were removed and frozen at 0, 24, 48, 72, and 96 hour marks. The final aliquot underwent DNA isolation and DNA polymerase chain reaction before gel electrophoresis.

Fourth pot study.

A pot study was performed by Ms. Motomura under the supervision of Dr. Shintaku to determine whether vermicompost, vermicompost tea or a preparation of indigenous microorganisms (IMO) could help to reduce populations of the ginger wilt pathogen R. solanacearum in naturally infested field soil. A 12-week trial began on June 16, 2011 and ended on  August 25, 2011. Soil samples were collected and relative populations of R. solanacearum were determined using the Enrichment-PCR method. A randomized block design with four replicates of each treatment was used. Weekly soil samples were collected from 2L pots and enriched over a five-day period with aliquots collected at 0, 24, 48, 72 and 96 hours, and then analyzed using PCR.

Objective 5. Conduct economic analysis of sustainable farming practices.

Initial Survey.

The initial producer survey was fielded in February 2011 during the first outreach event to educate producers about the project.

Second Survey.

The second survey of producers was fielded in March 2013 during the third outreach event to disseminate project results and distribute the third batch of bacterial wilt-free ginger. A brief presentation about the cultural practices that will assist producers in managing the spread of bacterial wilt of edible ginger was given. These practices were also featured on the project website and some are highlighted in videos found on the website. These practices included the following: 1) Site selection (wilt-free site, not down-slope from another ginger field); 2) Planting (avoid planting during wet weather); 3) Site preparation (use disease-free equipment and prepare site to drain well); 4) Planting disease-free seed pieces; 5) Limiting site traffic; 6) Using organic soil amendments; 7) Crop rotation (rotate ginger with crops that are not hosts to bacterial wilt); 8) Intercropping (interplant with crops that are not hosts to bacterial wilt); 9) Bio-fumigation (growing green manure crops); 10) Controlling other pests; and 11) Harvesting on-time.

Final Survey.

The final survey of ginger producers was distributed electronically or by mail to ginger producers during June 2014. Dr. Cox analyzed results of these three surveys.

Objective 6. Disseminate information and enhance farmer adoption of practices through a video and a web site.

Dr. Scot Nelson developed the informational website on ginger wilt and hired a private contractor to produce five YouTube videos on ginger. He also authored a comprehensive Extension publication on the disease.

Research results and discussion:

Objective 1. Demonstrate the importance of clean planting materials.

Ginger rhizomes that had been cleaned earlier of R. solanacearum during tissue-culture were multiplied in a disease-free medium using hydroponic culture during May through December of 2010-2012. They were harvested during January to February of 2011- 2013. Over 1,300 pounds over three years were distributed to commercial or educational growers.

Effect of shading or silicon on hydroponic production of ginger.

Shading was found to reduce growth of hydroponically grown ginger (Kratky et al., 2013). Two greenhouse studies did not indicate any improvement of ginger yield or quality due to the addition of silicon.

Four meetings were held for growers (commercial and backyard) to inform them of the wilt disease caused by Ralstonia solanacearum, the importance of planting wilt-free ginger seed pieces, keeping fields disease-free and how wilt-free ginger seed pieces were grown hydroponically. Meetings were held on February 22, 2011, February 26, 2011, March 6, 2012 and March 13, ­ 2013. Participant numbers were 23, 20, 28 and 33 growers, respectively.

Three scientific presentations were given at the national meetings of the American Society for Horticultural Science during September 25-28, 2011 and July 21-25, 2013 (Kratky et al., 2011; Motomura et al., 2011b, 2013). One scientific presentation was given at the national meeting of the American Phytopathological Society during during August 21-25,2011 (Motomura et al., 2011a).

Dr. Kratky published an article on how shading reduces yields of edible ginger grown using hydroponics (Kratky et al., 2013). Ms. White published an article on how to multiply wilt-free ginger using a simplified method of pot culture (White et al., 2013).

Objective 2. Demonstrate procedures to test fields for Ralstonia solanacearum.

We have shown that our methodology of bacterial extraction from soil followed by Enrichment-PCR is sensitive, reliable and cost-effective (Motomura, 2013). This methodology has been adopted by the Agricultural Diagnostic Service Center (ADSC) at the University of Hawaii at Manoa. The center now offers testing of R. solanacearum in soils and other growth media, in addition to Enzyme-Linked Immunoassay (ELISA) testing of ginger tissue samples. In 2012, 2013 and 2014 (to date), there have been six, four and eight, respectively, Enrichment-PCR assays conducted at ADSC.

Objective 3. Conduct field studies.

In the field trial conducted during 2011-2012, one plant in the field was found to have ginger wilt during August 2011, and it was removed from the field. At harvest, the row with the removed diseased plant was found to have infected rhizomes based on PCR although they appeared symptom-less. Average marketable yields (fresh weight) of three disease-free rows were 54,030 pounds per acre (60,680 kg/ha), with 20% loss due to unmarketable yields. In the row with ginger wilt (row 5), the marketable yield was only 16,600 pounds per acre (18,640 kg/ha) with 69% loss due to unmarketable yields.

In the second field study conducted during 2012-2013, total fresh weight yields in four plots ranged from 55,900 to 77,100 pounds per acre (62,800 to 86,600 kg per ha); marketable fresh weight yields ranged from 39,300 to 61,600 pounds per acre (44,100 to 69,200 kg per ha). The large percentage of unmarketable rhizomes (ranging from 21 to 30% of total fresh weight yield) were primarily due to damage caused by root-knot nematode (Meloidogyne incognita) and red rot caused by the fungus Pyrenochaeta sp. This field planting did not have any occurrence of bacterial wilt of ginger; however, other pests and diseases reduced fresh weight yields in all four plots by 21 to 30%.

Isolation and testing of antagonistic bacteria.

Suspensions of B. megaterium showed no inhibitory effect against R. solanacearum in plate inhibition assays. Serenade (a commercial B. subtilis preparation) was also tested for inhibitory effects at dilution rates of 1:40, 1:10 and undiluted. Inhibition was only noted in the undiluted test and was minor enough to be attributable to nutrient competition by the rapidly growing colony of B. subtilis.

Antagonistic Bacteriophages.

A number of plaques isolated from several soil samples were transferred to broth cultures of R. solanacearum, where they failed to significantly suppress bacterial growth. Our studies indicate that while lytic phages infecting R. solanacearum are widespread in East Hawaii field populations, the phages we isolated are unlikely to provide good field control of bacterial wilt.

Objective 4. Conduct greenhouse studies to determine the effectiveness of vermicomposts.

First pot study.

The results of the PCR analysis showed that despite inoculation with R. solanacearum, all samples tested negative for the pathogen. The negative PCR results raised many questions as to the mechanism of suppression in all treatments. Perhaps, the medium used (Promix BX) was itself suppressive. Also, the high temperatures in the greenhouse coupled with the use of conventional black pots could have exceeded the acceptable range for survival of Ralstonia. While these circumstances were problematic for our research, they warrant further investigation and could potentially lead to an alternative disease suppression strategy.

Second Pot Study.

Ginger inoculated with R. solanacearum and grown in pots substituted with 10% and 20% vermicomposts produced the highest yields both in non-symptomatic rhizomes (Figure 1) and overall yield (Figure 3). Ginger inoculated with R. solanacearum and grown in 1% and 5% vermicompost, produced rhizomes that were not significantly different than the control (0% vermicompost) (Figure 2). However, all of the treatments inoculated with R. solanacearum, including the control, showed symptoms of disease on the foliage and these ratings were not significantly different (Figure 4).

Third pot study.

There were four samples that were positive for R. solanacearum: 5, 20, and 40% vermicompost rates. The 20% and 40% vermicompost rates had the largest colonies of R. solanacearum, and were followed by another 20% vermicompost rate treatment and last by 5% vermicompost rate. Figure 5 shows that the symptoms of Ralstonia on the foliage, three weeks after inoculation, were evident on treatments that had 5%, 20% and 40% vermicomposts. Results showed that the incidence of R. solanacearum in the soil did not necessarily result in symptoms on the foliage of the plants. For instance, ginger plants grown in pots substituted with 5% vermicomposts showed no symptoms on the foliage (0) in Figure 5, although R. solanacearum was present in the soil.

In summary, ginger inoculated with R. solanacearum grown in pots substituted with vermicomposts at rates of 10% and 20% produced the highest yield when symptomless. Ginger inoculated with R. solanacearum and grown in pots substituted with 5% and 20% vermicomposts produced the least weight of rhizomes when ginger wilt symptoms were evident. Substitution with vermicomposts did not suppress the incidence of R. solanacearum as evident by the symptoms both on foliage and detection in soil by Enrichment-PCR, but their addition in the soil increased ginger yield despite presence of R. solanacearum.

Fourth pot study.

None of the treatments [vermicompost, vermicompost tea or a preparation of indigenous microorganisms (IMO)] showed a decrease in viable R. solanacearum populations throughout the 12 weeks. Rather, vermicompost tea at the mid and high rates showed a marked increase at weeks 9 and 12, while other treatments showed fluctuations in viable R. solanacearum populations from week to week, with no apparent trend. In conclusion, vermicompost, vermicompost tea or Indigenous Microorganisms (Imolizer) did not show an antagonistic effect on bacterial populations in soil in pots.

Successful defense of Master’s thesis.

Ms. Sharon Motomura’s (2013) thesis entitled “The Effects of Soil Amendments on the Survival of Ralstonia solanacearum in Hawaiian Soils” was accepted in April 2013. She graduated with a master’s degree in Tropical Conservation Biology and Environmental Science from the University of Hawaii – Hilo in May 2013. She has been hired by the University of Hawaii as a Junior Extension Agent for food crops on Hawaii Island; her areas of responsibility include ginger production.

 Objective 5. Conduct economic analysis of sustainable, farming practices.

Initial Survey.

The survey results indicated that bacterial wilt had a large impact on the behavior of survey respondents because it caused them to change their behavior in nearly all cases (only one relatively new part-time producer had not changed behavior), and in all cases respondents wanted to learn more about combating this disease. While the number of respondents was small, the destructive nature of the disease may have resulted in many producers losing interest in growing ginger. The interest demonstrated by two young producers who responded to the survey indicated that extending the results of this project holds promise for increasing ginger production over the long-term in Hawaii.

Second Survey.

Respondents to the survey reported on their use of the recommended practices aimed at managing the spread of bacterial wilt (see Table 1). Only intercropping was used by less than 50% of the respondents, with the other practices being used by at least 67% of the respondents.

Respondents reported that five years ago they planted 4.04 acres of ginger, on average. Only one respondent reported being affected by bacteria wilt at that time. Last year, respondents reported planting 4.26 acres of ginger and three reported being affected by bacterial wilt. Only one respondent reported no prior knowledge of bacteria wilt. Thus, the disease still affects respondents and ginger production did not appear to be increasing by much since the project started.

Seventy-five percent of the respondents said that they were interested in the testing service for seed and soil offered by the Agricultural Diagnostic Center at the University of Hawaii at Manoa. Three respondents were willing to pay an average of $5.33 a pound for bacterial wilt-free seed pieces. However, interest in and use of bacterial wilt-free seed pieces was relatively low.

The group discussion that followed the presentation and survey focused on how producers managed bacterial wilt in their operations. Some reported that they seek out virgin land that will not be infected and wanted more access to such land. Others relied on natural and organic farming methods to increase the disease suppressiveness of their fields. Clearly these two approaches were the most commonly used among the producers. The use of virgin land is not sustainable, although the use of alternative farming methods could be sustainable if effective approaches are found.

Final Survey.

The results indicated that that many survey respondents have found that growing edible ginger in the field is not profitable and/or presented too many challenges due to bacterial wilt. However, as a result of the educational events conducted for producers and other outreach done by the Cooperative Extension Service, several respondents have started or switched to the production of bacterial wilt-free seed ginger grown under greenhouse conditions.

An extensive educational effort aimed at introducing the production practices needed to grow edible seed ginger in pots and certifying the seed ginger as “bacteria wilt” free has resulted in producers launching a new industry that markets wilt-free ginger seed pieces. Survey results indicated that producers are marketing this product on the Island of Hawaii, across the State of Hawaii and on the U.S. mainland. In most of the U.S. mainland, edible ginger cannot be grown long enough for it to form dormant seed pieces; as a result, there is a demand each year for new seed pieces. The current price of field-grown, edible ginger on the Island of Hawaii is approximately $1 per pound; whereas the price of greenhouse-grown, bacterial wilt-free ginger seed pieces is approximately $5 per pound.

The price received for the bacterial wilt-free ginger seed pieces is enough to make the market profitable, and the ability to certify that the ginger is wilt-free ensures that the product is of high enough quality that producers can profitably export it out of the state. Since the seed ginger is also being sold across the State of Hawaii, it will facilitate edible ginger production on other islands where bacterial wilt is not a problem. While the field production of edible ginger on the Island of Hawaii may no longer represent a particularly viable option for producers, this project has helped to develop bacterial wilt-free seed ginger as a new, high valued product that supports the production of edible ginger in other parts of the state and the U.S. mainland.

Objective 6. Disseminate information and enhance farmer adoption of practices through a video and a web site.

We completed our ginger wilt website which also houses all of the project’s educational videos: http://www.ctahr.hawaii.edu/dnn/gingerwilt/Home.aspx. As of June 19, 2014, there were 3,809 site visits from 66 countries, with an average session duration of two minutes. For the YouTube videos, the number of views were: 719 views for the first YouTube video “The Ginger Project Overview”; 3,994 views for “Bernard Kratky’s Seed Production”; 315 views for “PCR Soil Testing”; 444 views for “Cultural Practice”; and 996 views for “Pepeekeo Harvest.” Dr. Nelson’s Extension publication on bacterial wilt of edible ginger may be found here: http://www.ctahr.hawaii.edu/oc/freepubs/pdf/pd-99.pdf .

Research conclusions:

During the four years of this project, we grew and distributed over 1,300 pounds of bacterial wilt-free ginger seed pieces to commercial growers, educators and backyard growers. We completed our ginger wilt website that also houses all of the project’s educational videos at: http://www.ctahr.hawaii.edu/dnn/gingerwilt/Home.aspx. This website is a resource for ginger growers to access current information on best methods to control ginger wilt, and by June 19, 2014, there were 3,809 site visits from 66 countries. We developed a method to test for presence of Ralstonia solanacearum in soil that is sensitive, reliable and cost-effective. It has been adopted by the University of Hawaii Agricultural Diagnostic Service Center. We have helped to develop bacterial wilt-free seed ginger as a new, high valued product that supports the production of edible ginger in other parts of the state and the U.S. mainland. We demonstrated that planting wilt-free ginger seed pieces into a field that tested free of R. solanacearum can result in good yields, although there are other pests that can reduce marketable yields. We conducted four informational meetings for growers and surveyed them for adoption of recommended practices to control ginger wilt. We published one extension paper on the effects of shading on hydroponically grown ginger and a second one on a simplified method to multiply bacterial wilt-free ginger in pots. We presented posters at two national meetings of the American Society for Horticultural Science during 2011 and 2013, and one poster at the national meeting of the American Phytopathological Society in 2011. Former graduate student Ms. Sharon Motomura completed her master’s thesis on the effects of soil amendments on the survival of R. solanacearum in Hawaiian soils, and she has been hired as a Junior Extension Agent of edible crops, including ginger.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

Scientific Publications:

Kratky, B.A., C. Bernabe, E. Arakaki, F. White, and S. Miyasaka. 2013. Shading reduces yields of edible ginger rhizomes grown in sub-irrigated pots. Coll. Trop. Agr. Human Resources, Univ. Hawaii, Honolulu, HI. Root Crops, RC-2. http://www.ctahr.hawaii.edu/oc/freepubs/pdf/RC-2.pdf .

Motomura, S. 2013. The effects of soil amendments on the survival of Ralstonia solanacearum in Hawaiian soils. M.Sc. thesis, Univ. Hawaii – Hilo, Tropical Conservation Biology and Environmental Science.

S. Nelson. 2013. Bacterial wilt of edible ginger in Hawaii. College of Tropical Agriculture and Human Resources, Cooperative Extension Service, PD-99.

White, F., S. Motomura, S. Miyasaka, B.A. Kratky. 2013. A simplified method of multiplying bacterial wilt-free edible ginger (Zingiber officinale) in pots. Coll. Trop. Agr. Human Resources, Univ. Hawaii, Honolulu, HI. Plant Disease, PD-93. http://www.ctahr.hawaii.edu/oc/freepubs/pdf/PD-93.pdf .

 

Scientific presentations:

Kratky, B.A., S.C. Miyasaka, and F. White. 2011. Production of edible ginger clean seed by sub-irrigation methods in Hawaii. Presentation (052) at American Society of Horticultural Science (ASHS), Sept. 25-28 2011, Waikoloa, HI. Available at: http://ashs.org/downloads/2011ASHS_Conference_abstracts.pdf . Accessed 11 June 2012.

Motomura, S., S. Nelson, S.C. Miyasaka, and M. Shintaku. 2013. Effect of composts on field soils affected by bacterial wilt of edible ginger in Hawaii. Presentation, American Society of Horticultural Science (ASHS), 21-25 July 2013, Palm Desert, CA.

Motomura, S., A. Read, N. Arancon, S. Miyasaka, and M. Shintaku. 2011a. Detection of Ralstonia solanacearumin Hawaiian field soils and evaluation of composts for suppressing pathogen populations. Poster session presented at the American Phytopathological Society (APS), 6-10 Aug. 2011, Honolulu, HI.

Motomura, S., Read, A., Arancon, N., Miyasaka, S., & Shintaku, M. 2011b. Effect of Composts on Field Soils Affected by Bacterial Wilt of Edible Ginger in Hawaii.Presentation (276) at American Society of Horticultural Science (ASHS), 25-28 Sept. 2011, Waikoloa, HI. Available at: http://ashs.org/downloads/2011ASHS_Conference_abstracts.pdf . Accessed 11 June 2012.

 

Other publications:

F. White and S. Miyasaka. 2011. Now is the time to prepare for planting ginger. West Hawaii Today.

Project Outcomes

Project outcomes:

Survey results indicated that that many respondents have found that growing edible ginger in soil is not profitable and/or presented too many challenges due to bacterial wilt. Field production of edible ginger on the Island of Hawaii may no longer represent a particularly viable option for producers, because farming virgin land is not sustainable, and cost-effective, alternative treatments to control bacterial wilt in the field have not been discovered.

However, as a result of the educational events conducted for producers and other outreach done by the Cooperative Extension Service, several respondents have started or switched to the production of bacterial wilt-free ginger seed pieces grown under greenhouse conditions. The current price of field-grown, edible ginger on the island of Hawaii is approximately $1 per pound, whereas the price of greenhouse-grown, bacterial wilt-free ginger seed pieces is approximately $5 per pound.

The price received for bacterial wilt-free ginger seed pieces is enough to make the market profitable, and the ability to certify that the ginger is bacterial wilt-free ensures that the product is of high enough quality that producers can profitably export it to the U.S. mainland. This project has helped to develop bacterial wilt-free seed ginger as a new, high valued product that supports the production of edible ginger in other parts of the state and the U.S. mainland.

Farmer Adoption

Several survey respondents have started or switched to the production of bacterial wilt-free ginger seed pieces grown under greenhouse conditions. The current price of field-grown, edible ginger on the island of Hawaii is approximately $1 per pound, whereas the price of greenhouse-grown, bacterial wilt-free ginger seed pieces is approximately $5 per pound. The price received for bacterial wilt-free ginger seed pieces is enough to make the market profitable, and the ability to certify that the ginger is bacterial wilt-free ensures that the product is of high enough quality that producers can profitably export it to the U.S. mainland. This project has helped to develop bacterial wilt-free seed ginger as a new, high valued product that supports the production of edible ginger in other parts of the state and the U.S. mainland.

Recommendations:

Areas needing additional study

One area that needs additional study is the further isolation and testing of antagonistic bacteria. While no antagonism between Bacillus and R. solanacearum was detected in our assays, stimulation of plant defense responses could play a significant role in Bacillus-induced plant disease resistance.

A second area that needs additional study is the efficacy of vermicomposts in increasing yields of ginger under field conditions. Although vermicompost treatments did not prevent infection of ginger by R. solanacearum, they did increase rhizome yields under greenhouse conditions.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.