Progress 09/01/20 to 08/31/24
Outputs
Target Audience:The project's target audience encompasses Extension agents and growers in Georgia, Florida, and neighboring states. The results of this project will be valuable to a range of stakeholders, including Extension specialists seeking to enhance their knowledge and advisory services, County extension agents working directly with growers, crop consultants and professionals looking for evidence-based solutions, and industry cooperators interested in advancing best practices of managing nematode and weed pests. The project aimed to drive regional and national adoption and impact by engaging with these stakeholders. Changes/Problems:N/A What opportunities for training and professional development has the project provided?This project was supported by a team of researchers, including two Ph.D. students, Josiah Marquez and Denis Gitonga, who were hired to work on the project. Additionally, Colin Wong, a postdoctoral fellow at the USDA-ARS in Byron, GA, contributed to a portion of the project. The team was further assisted by three research technicians/biologists and several research interns who played a crucial role in the project's success. How have the results been disseminated to communities of interest?The findings of this project were disseminated widely to stakeholders and the scientific community through various channels, including presentations at annual regional, national, and international conferences and meetings, County growers' meetings and extension agent training sessions, cover crop workshops and field days, scientific and extension publications, and industry magazines. This multi-faceted approach ensured that the results reached a broad audience, facilitating knowledge sharing and uptake among diverse stakeholders. What do you plan to do during the next reporting period to accomplish the goals?N/A
Impacts
What was accomplished under these goals?
The specific objectives of this project were 1) evaluate the efficacy of native Bacillus thuringiensis (Bt) crystal proteins, bacterial metabolites associated with entomopathogenic nematodes (EPNs), and OMRI-certified bionematicides for control of root- knot nematode (RKN), Meloidogyne incognita under in vitro and greenhouse conditions, 2) evaluate the effect of summer and winter cover crops on the population density of nematodes and weeds under field conditions, 3) integrate the best practices of cover cropping, most effective biological products and EPN bacterial metabolite to control nematodes in organic production of vegetables, and 4) evaluate the economic profitability of the developed practices. The outcomes of this project are summarized below. Three studies were conducted to meet the first objective: First, we examined the nematicidal effects of spore/crystal proteins from four B. thuringiensis strains against RKNs. Thestrains were isolated from U.S. soils and sporulated in PGSM medium. Then the expression of Cry5B, Cry6A, Cry14A, and Cry21A proteins was confirmed by SDS-PAGE. Each of two separate bioassays involved 100 M. incognita second-stage juveniles (J2) exposed to various concentrations (25, 50, or 100 µg/ml) of Bt proteins. Negative and positive controls included water, non-crystal-forming Bt strain HD1 (4D8), and Fluopyram, respectively. After 48 and 96 hrs, Cry5B showed the highest nematicidal activity, followed by Cry6A, with Cry14A and Cry21A showing the least. Nematode mortality was significantly higher after 96 hrs, with only 100 µg/ml being the most effective concentration. This suggests that Bt Cry proteins have potential as biological control agents against PPNs, warranting further studies in greenhouse and field conditions. Next, we evaluated metabolites from Xenorhabdus szentirmaii and X. bovienii bacteria on cabbage against M. incognita under different application timings [5 days before planting (DBP) and at planting (AP)] in greenhouse and screenhouse conditions. For comparison, bionematicides, (MeloCon WG and Majestene)and a chemical nematicide, Vydate, were only applied at planting. Plants treated with only water served as untreated check. Plants were infected with 1,000 RKNs, soil-drenched with metabolites or nematicides, and grown for 450-degree days at 10°C to complete two generations. The metabolites and Vydate significantly reduced root galling and egg counts/gram of root compared to Majestene and MeloCon, particularly when applied 5 DBP in the greenhouse. Both metabolites and Vydate reduced egg counts at AP and 5 DBP in the greenhouse, but no differences were observed in the egg counts between the metabolites and Vydate at 5 DBP in the screenhouse, showing potential for nematode control under varying application timings. Lastly, the efficacy of eight OMRI-certified bionematicides (Majestene, TerraNeem, AzaGuard, Molt-X, NemOmex, EcoWorks, Monterey, and Promax) was tested on M. incognita in tomatoes in the greenhouse for eight weeks. AzaGuard and Majestene improved root weights, with Monterey showing the lowest root weights and galling indices. Also, AzaGuard and TerraNeem- treated plants had the lowest eggs/gm of roots compared to the positive control. Field trials were recommended for further exploration of AzaGuard, EcoWorks, NemOmex, and Promax. The second objective was accomplished by conducting the following two field trials. A field study (2019-2021) assessed the effects of cover crops, weedy fallow rotations, and tillage practices on soilborne diseases and nematodes in spring tomatoes, fall squash, and winter cabbage. The trialused a split-plot 2 × 4 factorial randomized complete block design (RCBD), with shallow or deep tillage applied to whole plots. Subplots included rotation type (cover crop or weedy fallow) and season, with spring or fall sunn hemp and winter rye as cover crops. Sunn hemp and weedy fallow rotations significantly reduced RKN populations and root galling in the first vegetable crop, regardless of tillage. These rotations had limited impact on fungal pathogens. Fall-planted sunn hemp led to higher plant biomass and reduced galling in the second crop. Both spring and fall sunn hemp increased yields, while winter rye significantly reduced ring nematode (Mesocriconema spp.) populations in the first crop. Deep tillage reduced fungal pathogens (Rhizoctonia solani and Sclerotinia sclerotiorum) and lowered stubby-root nematode (Nanidorus minor) populations. Sunn hemp was especially effective in suppressing M. incognita. The study suggests sunn hemp is more effective than winter rye in suppressing RKNs, particularly in the fall, but both cover crops had limited effects on fungal pathogens. A two-year field study (2021-2022) evaluated winter cover crops and a bioherbicide for managing PPNs and weeds. The trials were conducted during two consecutive winter seasons, using oilseed radish, oat, rye, mustard, a rye-oat mix, and fallows (with and without weeds), each replicated five times. Cover crops were incorporated at 90 and 120 days. Rye and oat, especially in combination, significantly reduced M. incognita populations and suppressed weeds like corn spurry. Mustard and radish had variable effects on nematodes, sometimes increasing populations. Extending cover crop duration to 120 days increased nematode populations but reduced weed densities. The study highlights rye and oat as effective cover crops for nematode and weed control in organic vegetable systems. Two field trials explored integrating nematode-suppressive cover crops ('Crescent Sun' sunn hemp and 'Sweet Six BMR' sorghum-sudangrass) with three bionematicides (AzaGuard, Promax, EcoWorks) and a metabolite from X. bovienii (XB) bacteria for managing PPNs in organic zucchini. Treatmentsincluding two cover crops, bionematicides, and controls, were arranged in RCBD with five replications. Results showed that combining sorghum-sudangrass and sunn hemp with Promax and EcoWorks significantly reduced Meloidogyne and Hoplolaimus populations compared to fallow treatments, though Criconema populations increased in sorghum-sudangrass plots. Weedy fallow and the sunn hemp + sorghum-sudangrass + XB treatments had the highest nematode populations. No significant yield differences were observed. This suggests combining cover crops with bionematicides is effective, though cover crop selection is crucial to avoid increasing specific nematode populations. In addition, economic analyses were performed to address the fourth objective of this project. For an economic analysis, we synthesized results from field trials with current market prices for inputs and commodities. This included evaluating the returns of using cover crops to improve the profitability of organic zucchini production. Market prices were sourced from recent University of Georgia enterprise budgets (2022-2024), USDA data, and University Extension specialists. Trials integrated sunn hemp, sorghum-sudangrass, and four bionematicides. Establishment and removal costs for cover crops were estimated at $160 per acre, while bionematicide prices ranged from $20 to $160 per acre. Although cover crops and bionematicides increased per-acre costs, a statistically significant yield increase could enhance profitability due to zucchini's high market value. Conventional zucchini in Georgia fetches a median price of $13.00 per 30-lb box, with organic growers earning a 30% premium. The trials did not show a clear advantage for one cover crop, but AzaGuard consistently performed well. To cover additional costs, 300 lbs more per acre would be needed at the median price. At higher prices, this drops to 280 lbs; at lower prices, it rises to 350 lbs. In summary, while no definitive management strategy emerged from the trials, the high market value of organic zucchini offers potential profitability, which may offset the extra input and management costs.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Gitonga, D., Hamidi, N., and A. Hajihassani, A. 2021. Efficacy of certified bionematicides for control of Meloidogyne incognita in the greenhouse conditions. Journal of Nematology 53: 11. .
- Type:
Conference Papers and Presentations
Status:
Awaiting Publication
Year Published:
2024
Citation:
Jagdale, G. B., Wong, C., Hajihassani, A. and Shapiro-Ilan, D. 2024. Influence of bacterial metabolites from entomopathogenic nematode antagonism against Meloidogyne javanica in tomato under greenhouse conditions. Plant Health 2024- Annual Meeting of the American Phytopathological Society, Memphis, TN July 27- 30, 2024.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2021
Citation:
Marquez, J., and Hajihassani, A. Pyramiding cover crop rotation of sunn hemp or rye with tillage practices for suppression of nematodes, fungal soil-borne diseases, and weeds in a bare-ground vegetable production system. The 66th Annual Conference on Soilborne Plant Pathogens and the 51st Annual Statewide California Nematology Workshop, March 23-24, 2021.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2022
Citation:
Hajihassani, A., Timper, P., and Shapiro-Ilan, D. 2022. Effects of application timing on the efficacy of Xenorhabdus metabolites for control of Meloidogyne incognita. The 7th International Congress of Nematology, 1-6 May 2022, Antibes Juan-Les-Pins, France.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2022
Citation:
Gitonga, D., Hamidi, N., and Hajihassani, A. Evaluation of the effect of winter cover crops on population density of Meloidogyne incognita under field conditions. Annual Meeting of the Society of Nematologists. September 26-29, 2022, Anchorage, Alaska.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2022
Citation:
Marquez, J., Coolong, T.W. Dutta, B., and Hajihassani, A. Root-knot nematode suppression and effects on soil food web by cover crop and tillage practices in a bare-ground vegetable production system. 7th International Congress of Nematology, May 1-6, 2022. Antibes Juan-les-Pins, France.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2024
Citation:
Hajihassani, A. 2024. Effects of off-season winter cover crops and in-season nematicide application on plant-parasitic nematodes. Annual Meeting of American Society for Horticultural Science. September 23-27, 2024, Honolulu, Hawaii.
- Type:
Journal Articles
Status:
Published
Year Published:
2023
Citation:
Marquez, J. and Hajihassani, A. 2023. Successional effects of cover cropping and deep tillage on suppression of plant-parasitic nematodes and soilborne fungal pathogens. Pest Management Science. 79: 2737-2747.
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Marquez, J., Hajihassani, A., and Davis, R. F. 2022. Evaluation of summer and winter cover crops for variations in host suitability for Meloidogyne incognita, M. arenaria and M. javanica. Nematology, 24: 841-854.
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Kicklighter, J., Kichler, J.M., and Hajihassani, A. 2020. On-farm evaluation of sunn hemp cover cropping on root-knot nematodes, 2018. Plant Disease Management Reports, 14: N030.
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Progress 09/01/22 to 08/31/23
Outputs
Target Audience:The target audience for this project is organic vegetable growers and producers in Georgia, Florida, and the neighboring Southern states. However, the results will be used by extension specialists, county extension agents, crop consultants, Ag. Professionals and the industry. Changes/Problems:Because of the relocation of the former PD from Georgia to Florida, we were unable to include an on-farm trial because no certified organic vegetable farm with root-knot nematode infestation was found in South Florida. What opportunities for training and professional development has the project provided?This project has helped to fund and train two graduate students. Also, two research interns from minority-serving institutions (Miami Dade College and Broward College) were hired to work on this research. All students were trained and integrated in every aspect of the project. One post-doc and one technician are also assisting with the project. How have the results been disseminated to communities of interest?Dr. Hajihassani presented some results from this project on using cover crops for nematode control at the Florida Ag Expo attendees (>250) at the Gulf Coast Research and Education Center on November 2, 2022. The results from the bacterial metabolite research were shared with others at the Entomological Society of America, Southeastern Branch, March 12-15, 2023, in Little Rock, Arkansas. Two abstracts were presented at the 7th International Congress of Nematology and Society of Nematologists annual meeting. What do you plan to do during the next reporting period to accomplish the goals?We are currently conducting field studies in two locations in central and south Florida on the integration of cover crops and bionematicides for nematode control. These experiments will be completed in spring 2024. Also, the economic analyses of the project will be completed. A manuscript will be prepared for submission and results will be presented at field days and scientific meetings.
Impacts
What was accomplished under these goals?
A field study in a randomized complete block design with five treatments [oilseed radish (cv. Carwoodi), oat (Tachibuki), rye (Wrens Abruzzi), mustard (Caliente), and rye-oat mixture] was established to examine the evaluation of the effect of winter cover crops on the population density of root-knot nematode (RKN), Meloidogyne incognita. Two fallows (with and without weeds) were included as controls. The cover crops were planted in early October and terminated 90 and 120 days after planting. Cover crop residues were then incorporated into the soil by a moldboard plow to achieve a maximum volume of allelopathic and/or nematicidal activity. RKN population densities were examined before planting, at termination, and two weeks after incorporating the crop residue into the soil. Biomass accumulation was determined using 10 random representative plants at the termination of cover crops. Oven-dried aboveground parts of plants were weighed, and their root systems were assessed for RKN gall severity. The RKN abundance differed (P < 0.01) between the two years (2021 and 2022). In 2021, there was an increase in the nematode population (P < 0.05) when the cover crops were left longer (120 days) in the field compared to a shorter period (90 days). The incorporation of cover crops in the soil was not significant in terms of RKN abundance in both trials. In 2021, rye-oat had the lowest RKN abundance (P < 0.01) compared to other treatments, while radish had the highest abundance (P < 0.01). There were no significant differences in the nematode density between rye, mustard, and the two fallows. In 2022, RKN abundance was not significantly affected by either the termination period (90 and 120 days) or cover crop incorporation in the soil. However, there were differences among the treatments with the fallow with weeds having the highest RKN abundance (P < 0.01) compared to other treatments. Oat, rye, and fallow without weeds had the lowest RKN abundance. The cover crop biomass was significantly higher in 2021 than in 2022, with radish having the highest biomass. Mustard had a higher galling index (P < 0.01) than other cover crops in both 90 and 120 termination days, while oat, rye, and rye-oat mixture had the lowest galling index. We found that rye and rye-oat mixture can reduce M. incognita populations in the soil. Two plasticulture field trials were conducted to evaluate the nematicidal efficacy of selected commercially available bionematicides against M. incognita. The products included AzaGuard, EcoWorks, NemOmex, Promax, and Pendi selected using a greenhouse screening test, and Vydate was used as the standard control. The trials were conducted in a field naturally infested with Meloidogyne incognita. The trial consisted of two bionematicide application regimes (calendar vs. nematode development based). The experiment utilized a randomized complete block design with five replicates per treatment. The average daily soil temperature at a depth of 5, 10, and 20 cm was assessed for the nematode development-based application. Accumulated degree days of 370 to 380 were achieved for M. incognita to complete one generation, at which the nematicides were applied according to the label through the drip irrigation system. Soil nematode abundances were assessed three times at pre-plant, midseason, and harvest, while root galling was assessed at mid-season and harvest. The crop yield was also determined by harvesting cucumber three times during the season. Nematode development-based applications had lower M. incognita density at harvest than calendar-based applications. Moreover, AzaGuard, EcoWorks, and Vydate had the lowest nematode density compared to other treatments. The gall index and yield differed significantly among all treatments in both application regimes. These results suggest that the nematode development-based application reduces M. incognita population density and the frequency of application compared to calendar-based applications. Additionally, AzaGuard and EcoWorks consistently reduced M. incognita population density under greenhouse and field conditions; therefore, they can be used in an integrated pest management approach to control M. incognita. In another study, we investigated the potential use of crystal toxins of Bacillus thuringiensis (Bt) to control root-knot nematode, Meloidogyne incognita. Four different native Bt strains expressing nematode-active toxins from different soils collected from all over the world were sporulated for 96 hours at 30° C in PGSM medium and their nematicidal effects were studied in vitro against the nematode.These strains express Cry5B, Cry6A, Cry14A, and Cry21A proteins known to be active against nematodes, and expression of the proteins was confirmed by SDS PAGE. In addition, the canonical B. thuringiensis HD1 strain 4D8 cured of all Cry protein plasmids (i.e., expresses no Crystal proteins) was similarly grown.The bioassays were conducted in 24-well plates. M. incognita J2 was exposed to 25, 50, and 100 ug/ml of the four Bt Cry proteins. Each well received 500 μl of each Bt concentration, to which 90 - 100 nematodes in 70 μl distilled water were added. Each treatment was replicated four times and the experiment was performed twice. Negative controls included water and non-crystal forming Bt; positive control included a known nematicide (velum). The mortality was determined visually under an inverted microscope at 48 hours and 96 hours post-exposure.Nematodes were considered dead if their body was straight and they did not respond to being touched by a small probe. The mortality rates (M) of J2 were calculated using Abbott's formula. We found that the crystal proteins of isolate Cry5B showed the highest nematicidal activities across all the concentrations followed by Cry6A while crystal proteins of isolate Cry14A and Cry21A had the least nematode mortality in all Bt concentrations. Moreover, after examining the time of exposure in the four Bt crystal proteins, it was evident that 96 hours post-exposure had a significant increase in nematode mortality compared to 48 hours post-exposure across all treatments with 100 ug/ml being the most effective concentration compared to 25 ug/ml and 50 ug/ml. It was also observed that the nematodes did not recover after 24 hours upon adding 1ml water into wells containing 500 μl of each Bt concentration.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2023
Citation:
Marquez, J. and Hajihassani, A. 2023. Successional effects of cover cropping and deep tillage on suppression of plant-parasitic nematodes and soilborne fungal pathogens. Pest Management Science. https://doi.org/10.1002/ps.7450
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Hajihassani, A., Gitonga, Timper, P., and Shapiro-Ilan, D. Effects of application timing on the efficacy of Xenorhabdus and Photorhabdus metabolites for control of Meloidogyne incognita. 7th International Congress of Nematology, May 16, 2022. Antibes Juan-les-Pins, France.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2023
Citation:
Gitonga, D., and Hajihassani, A. 2023. Efficacy of bionematicides against Meloidogyne incognita under greenhouse and field conditions 2023 Society of Nematologists meeting, July 9-14, Columbus, OH.
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Marquez, J., Hajihassani, A., and Davis, R. F. 2022. Evaluation of summer and winter cover crops for variations in host suitability for Meloidogyne incognita, M. arenaria and M. javanica, Nematology, 24: 841-854. doi: https://doi.org/10.1163/15685411-bja10172
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Progress 09/01/21 to 08/31/22
Outputs
Target Audience:The target audience for this project is Extension agents and growers in Georgia, Florida, and the neighboring states. The results will be used by extension specialists, county extension agents, crop consultants and professionals, and industry cooperators to manage nematode problems. Changes/Problems:Since the former PD, Dr. Hajihassani, moved from the University of Georgia to the University of Florida and the presence of different environmental conditions between South Georgia and South Florida, the objective of the effects of summer cover crops for the control of plant-parasitic nematodes and weeds cannot be completed. We also should search for, if available, an organic vegetable grower in South Florida to conduct on-farm trials (last objective) for integrated management of nematodes and weeds using both biopesticides and cover crops. If no organic vegetable farm is located, this objective will be examined in a certified organic field in one of the University of Florida's research centers. What opportunities for training and professional development has the project provided?A Ph.D. student (Denis Gitonga) was hired from the proposal and is currently working on the project at the University of Georgia. This student was transferred with Dr. Hajihassani to the University of Florida and will be working on completing the laboratory and field studies. A postdoctoral fellow (Colin Wong) is currently working on a portion of the project at the USDA-ARS in Byron, GA. In addition, two research technicians/biologists were able to assist in the preparation of Bt cry isolates and EPN metabolites at the UMass Medical School and USDA-ARS, Byron, GA, respectively. How have the results been disseminated to communities of interest?The results of the study on the effect of bacterial symbionts of entomopathogenic nematodes on root-knot nematode control were presented by Dr. Hajihassani at the Seventh International Congress of Nematology in May 2022 in Antibes Juan-Les-Pins, France. In addition, Dr. Hajihassani presented the findings from this project at multiple county growers' meetings in Georgia in Winter 2021. Also, he developed a virtual cover crop training workshop and presented the results to the University of Georgia's Extension agents. Dr. Hajihassani also was invited to the Southeast Regional Fruit and Vegetable Conference in Savannah in January 2022 and shared part of the results with growers, Extension agents, the agriculture community, and the industry. An article was published in AgNet Media magazine titled "Cover Crops for Summer Nematode Management". This article reveals some of the results from this project and can be found on the following link: https://specialtycropindustry.com/cover-crops-for-summer-nematode-management/ What do you plan to do during the next reporting period to accomplish the goals?Conduct greenhouse studies for root-knot nematode control using Bt toxins. Conduct field studies using the integrated management practices developed in this project. Conduct the economic analysis, prepare manuscripts, and continue sharing the results with stakeholders and the scientific community.
Impacts
What was accomplished under these goals?
Bioassay to test the effect of Bacillus thuringiensis on mortality of Meloidogyne incognita in vitro. To investigate the potential use of crystal toxins of Bacillus thuringiensis (Bt) to control plant-parasitic nematodes, we studied the nematicidal effects of spore/crystal proteins of four Bt isolates were studied in vitro against Meloidogyne incognita nematode. Four different native Bt strains expressing nematode-active toxins from different soils collected in the US were sporulated for 96 hours at 30° C in PGSM medium. These strains express Cry5B, Cry6A, Cry14A, and Cry21A proteins known to be active against nematodes, and expression of the proteins was confirmed by SDS PAGE. In addition, the canonical B. thuringiensis HD1 strain 4D8 cured of all Cry protein plasmids (i.e., expresses no Crystal proteins) was similarly grown. The bioassays were conducted in 24-well plates. M. incognita J2 was exposed to 25, 50, and 100 ug/ml of the four Bt Cry proteins. Each well received 500 μl of each Bt concentration, to which 90 - 100 nematodes in 70 μl distilled water were added. Each treatment was replicated four times and the experiment was performed twice. Negative controls included water and non-crystal forming Bt; positive control included a known nematicide (Velum). The nematode mortality rate was determined visually under an inverted microscope at 48 and 96 hours post-exposure. The crystal proteins of isolate Cry5B showed the highest nematicidal activities across all the concentrations followed by Cry6A, while crystal proteins of isolate Cry14A and Cry21A had the least nematode mortality in all Bt concentrations. Moreover, after examining the time of exposure in the four Bt crystal proteins, it was evident that 96 hours post-exposure had a significant increase in nematode mortality compared to 48 hours post exposure across all treatments with 100 ug/ml being the most effective concentration compared to 25 ug/ml and 50 ug/ml. It was also observed that the nematodes did not recover after 24 hours upon adding 1ml water into wells containing 500 μl of each Bt concentration. ?Effects of metabolites cultured from the bacterial symbionts of entomopathogenic nematodes on root-knot nematodes. Bacteria were isolated from five different strains of entomopathogenic nematodes, all of which are commercially available. Bacteria were grown for 8 days, and the exo-metabolites found in the growth medium were used for the experiments. The metabolite broths and control treatments were co-applied with the root-knot nematode, Meloidogyne incognita to young tomato plants (Rutgers, a susceptible variety) grown in the greenhouse at the USDA-ARS in Byron, GA. The treatments were terminated 8 weeks post-inoculation and measurements of the plants were conducted as well as quantification of the root-knot nematode populations. The treatments included ten individual plants each split over two trials. The metabolite treatments appear to have had an impact on the tomato plants and nematode populations. Metabolite treatments had lower quantities of nematodes and eggs than the nematode control and more than the broth-only control. Plant growth parameters were lower in the nematode control, and the metabolite treatments had similar values to those of the broth-only control. There are potentially beneficial effects of the metabolites to plant growth over the broth-only control, but more tests are required to determine if this effect is real. We also evaluated the efficacy of application timing [5 days before planting (DBP) and at plant (AP)] of two bacterial metabolites, Xenorhabdus szentirmaiiandX. bovienii, against the root-knot nematode Meloidogyne incognitaon cabbage in two environmental conditions (screenhouse and greenhouse) at the University of Georgia, Tifton campus, GA. At transplant, recommended applications ofPaecilomyces lilacinusstrain 251 (MeloCon WG) and secondary metabolites ofBurkholderia rinojensisstrain A396 (Majestene) were also included in the trials for comparison. Plants were infected with 2,500 M. incognita second-stage juveniles (J2), soil-drenched with the metabolites or nematicides, and grown for 450-degree days using a base temperature of 10 °C to complete two generations. Plants treated with water were considered the untreated check, and each treatment had six replications arranged in a completely randomized design. In the greenhouse, the X.szentirmaiimetabolite at 5 DBP had a lower (P< 0.05) root gall rating than the control. Both metabolites had significantly lower root galling compared to Majestene, MeloCon, and control treatments. The metabolites reducedM. incognitaegg counts per gram of root compared to other treatments in the greenhouse; however, there were no differences in the egg count between the metabolites. In the screenhouse, the AP application ofX.szentirmaii and X. bovieniiat 5 DBP reduced the egg count compared to Majestene and the control; however, no differences in the egg counts between the metabolites were observed. Suppressive effects of winter cover crops on root-knot nematode populations in the field conditions. Two independent trials were conducted in winter 2021 and 2022 in a field naturally infested with the root-knot nematode (RKN; Meloidogyne incognita) to determine the effect of different termination timing of cover crops on nematode development in South Georgia, USA. The study utilized a randomized complete block design with five treatments [oilseed radish (cv. Carwoodi), oat (Tachibuki), rye (Wrens Abruzzi), mustard (Caliente), and rye-oat mixture]. Two fallows (with and without weeds) were included as controls. Each plot was 5 ft wide and 25 ft long with 6 ft between them. The cover crops were planted in early October and terminated 90 and 120 days after planting. Cover crop residues were then incorporated into the soil by a moldboard plow to achieve a maximum volume of allelopathic and/or nematicidal activity. RKN population densities were examined before planting, at termination, and two weeks after incorporating the crop residue into the soil. Biomass accumulation was determined using 10 random representative plants at the termination of cover crops. Oven-dried aboveground parts of plants were weighed, and their root systems were assessed for RKN gall severity. The RKN abundance differed significantly between the two years (2021 and 2022). In 2021, there was an increase in the nematode population (P < 0.05) when the cover crops were left longer (120 days) in the field compared to a shorter period (90 days). The incorporation of cover crops in the soil was not significant in terms of RKN abundance in both trials. In 2021, rye-oat had the lowest RKN abundance compared to other treatments, while radish had the highest abundance. There were no significant differences in the nematode density between rye, mustard, and the two fallows. In 2022, RKN abundance was not significantly affected by either the termination period (90 and 120 days) or cover crop incorporation in the soil. However, there were differences among the treatments with the fallow with weeds having the highest RKN abundance (P < 0.01) compared to other treatments. Oat, rye, and fallow without weeds had the lowest RKN abundance. The cover crop biomass was significantly higher in 2021 than in 2022, with radish having the highest biomass. Mustard had a higher galling index (P < 0.01) than other cover crops in both 90 and 120 termination days, while oat, rye and rye-oat mixture had the lowest galling index. In conclusion, rye and rye-oat mixture can reduce M. incognita populations in the soil. Additionally, leaving cover crops in the field for a longer period can lead to nematode population build-up that would negatively impact consecutive cash crops.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Marquez, J., and Hajihassani, A. Pyramiding cover crop rotation of sunn hemp or rye with tillage practices for suppression of nematodes, fungal soil-borne diseases, and weeds in a bare-ground vegetable production system. 66th Annual Conference on Soilborne Plant Pathogens and the 51st Annual Statewide California Nematology Workshop, March 23-24, 2021.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Gitonga, D., Hamidi, N., and A. Hajihassani, A. 2021. Efficacy of certified bionematicides for control of Meloidogyne incognita in the greenhouse conditions. Journal of Nematology 53: 11.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Hajihassani, A., Timper, P., and Shapiro-Ilan, D. 2022. Effects of application timing on the efficacy of Xenorhabdus metabolites for control of Meloidogyne incognita. The 7th International Congress of Nematology, 1-6 May 2022, Antibes Juan-Les-Pins, France.
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Progress 09/01/20 to 04/04/22
Outputs
Target Audience:This project has diverse audiences of growers, cooperative extension personnel, scientific community, crop consultants and professionals, and industry cooperators. Changes/Problems:The PI of this project, Dr. Abolfazl Hajihassani, left the University of Georgia in January 2022 to start a new nematology program at the University of Florida (UF) Fort Lauderdale Research and Education Center. The PI is currently working with USDA-NIFA on the possibility of transferring the grant to UF and modifying objectives to continue completing the project. Due to this fact, we will need to request USDA-NIFA for a six-month to one-year No-Cost Extension to be able to complete the project. What opportunities for training and professional development has the project provided?A Ph.D. student (Denis Gitonga) was hired from the proposal and is currently working on the project at the University of Georgia. This student will be transferred to the University of Florida (UF) in May 2022 to continue working on this project's objectives. In addition, a temporary technician will be hired at the UF to assist in the completion of this project. Three research technicians/biologists were able to assist in the preparation of Bt cry isolates and EPN metabolites at the UMass Medical School and USDA-ARS, Byron, GA, respectively. How have the results been disseminated to communities of interest?The greenhouse results on the efficacy of bionematicide products in the control of root-knot nematodes were presented as a poster at the annual meeting of the Society of Nematologists in Alabama in the summer of 2021. Data from greenhouse studies were also presented at the Southeast Regional Fruit and Vegetable Conference on January 7, 2022, in Savannah, GA. In addition, a training workshop "Cover crop production and soil health" was established on July 6, 2021, and the preliminary results from the cover crop study were shared with 21 extension agents from Georgia. What do you plan to do during the next reporting period to accomplish the goals?Complete nematode bioassays, conduct the economics analysis, prepare manuscripts, and present the results at appropriate scientific or extension meetings.
Impacts
What was accomplished under these goals?
We evaluated the efficacy of application timing [5 days before planting (DBP) and at plant (AP)] of two bacterial metabolites, Xenorhabdus szentirmaiiandX. bovienii, against the root-knot nematode Meloidogyne incognitaon cabbage in two environmental conditions (screenhouse and greenhouse) at the University of Georgia (UGA), Tifton campus, GA. At transplant, recommended applications ofPaecilomyces lilacinusstrain 251 (MeloCon WG) and secondary metabolites ofBurkholderia rinojensisstrain A396 (Majestene) were also included in the trials for comparison. Plants were infected with 2,500 M. incognita second-stage juveniles (J2), soil-drenched with the metabolites or nematicides, and grown for 450 degree days using a base temperature of 10 °C to complete two generations. Plants treated with water were considered the untreated check, and each treatment had six replications arranged in a completely randomized design. In the greenhouse, the X.szentirmaiimetabolite at 5 DBP had a lower (P< 0.05) root gall rating than the control. Both metabolites had significantly lower root galling compared to Majestene, MeloCon, and control treatments. The metabolites reduced (P< 0.05)M. incognitaegg counts per gram of root compared to other treatments in the greenhouse; however, there were no differences in the egg count between the metabolites. In the screenhouse, the AP application ofX.szentirmaii and X. bovieniiat 5 DBP reduced the egg count compared to Majestene and the control; however, no differences in the egg counts between the metabolites were observed. Two independent greenhouse experiments were conducted at the UGA Tifton campus, GA to evaluate the nematicidal efficacy of eight commercially available products (Majestene, TerraNeem, AzaGuard, Molt-X, NemOmex, EcoWorks, Monterey, and Promax) against Meloidogyne incognita. After eight weeks, shoot length, shoot dry weight, fresh root weight, root gall severity using a scale of 0 to 5, and reproduction factor (Pf/Pi) were evaluated. There was no significant difference in the dry shoot weight and shoot length among all the treatments. AzaGuard and Majestene had the highest (P < 0.05) root weight, while Monterey had the lowest root weight compared to both control checks. Monterey had the lowest (P < 0.05) galling index, followed by AzaGuard and Molt-X compared to the positive control. However, Monterey had undesirable effects on the root system resulting in low galling severity and egg counts. The number of eggs per gram of root at the end of the experiments varied greatly and ranged from 1806 to 4815. Azaguard had the lowest (P < 0.05), while TerraNeem had the highest eggs per gram of roots compared to the positive control. AzaGuard outperformed all the other bionematicides and was selected along with a few other potential products for the field trials to manage Meloidogyne spp. in organic vegetables. A field study was conducted using cucumber in a certified organic field naturally infested with Meloidogyne spp., at the UGA Horticulture Hill Farms, Tifton, GA in April 2021. The trial utilized a randomized complete block design with seven treatments and five replicates. The experimental treatments used were: untreated control, AzaGuard, NemOmex, EcoWorks, Pendi, and Promax. RKN population was not significantly (P = 0.0933) affected by nematicide application. Despite a lack of statistically significant RKN reduction, Azaguard and Ecoworks were the best compared to other products. The root galling was significantly less treated with Azaguard compared to other products including the untreated check. On the other hand, Pendi showed a significantly high galling index compared to other products but with control. Neither of the biological nematicides significantly (P=0.5806) affected the cucumber yield. However, numerically Ecoworks performed better compared to other treatments and the untreated check. Overall, the best two products were Ecoworks and Azaguard while the worst two were; Promax and Nemomex. This trial was repeated in July 2021, but the data were not included in this report due to time constraints. Another study was conducted in a certified organic field naturally infested with Meloidogyne spp., at the UGA Horticulture Hill Farms, Tifton, GA to determine the effect of different termination timing of cover crops on the development and population of nematodes and weed density. Winter cover crops were grown in the field in early November 2020 and terminated (harvested) 90 and 120 days after planting. Cover crop residues were then incorporated into the soil by a moldboard plow to achieve maximum allelopathic and/or nematicidal activity. Two weeks after incorporation, planting beds (false seedbeds) were prepared to stimulate weeds to germinate. Data collected included cover crop biomass accumulation, the abundance of plant-parasitic nematodes, root galling severity, and weed density. A significant difference (P = 0.0116) in RKN populations was found between the interaction effects (Days in the field "90 & 120" and the cover crops) when analyzed using a two-way ANOVA. There was a significant (P = 0.0436) increase in RKN population when the cover crops were left longer (120 days) in the field compared to a shorter period (90 days), especially for radish. There were no significant differences found between the interaction effects (before and after) cover crop incorporation in the soil trials (90 and 120 cover crops. When pooling and analyzing the data from the two trial periods using a one-way ANOVA, significant differences were found among the treatments. Further analysis using Tukey HSD test, Rye-Oat had the lowest RKN population compared to other cover crops while Radish (P = 0.0006) had the highest population of RKN. Rye, Mustard, and Oat did not differ significantly from one another, and neither were any significant differences between the three treatments and the fallow (with weeds and without weeds). No significant difference in free-living nematode populations was found between the interaction effects (Days in the field "90 & 120" and the cover crops) when analyzed using a two-way ANOVA. Once pooling and analyzing the data from the two trial periods using a one-way ANOVA, significant differences (F = 4.8002; P = 0.0304) were found between 90 and 120 days. Generally, 90 days had more free-living nematodes compared to 120 days. There was a significant difference (F = 2.5793; P = 0.022) between the before and after incorporation of cover crops. Amongst all the cover crops, Rye, Radish and Mustard had a significant increase in the number of free-living nematodes after incorporation into the soil compared to before incorporation. No significant difference in cover crop biomass was found between the interaction effects (Days in the field "90 & 120" and the cover crops) when analyzed using a two-way ANOVA. When pooling and analyzing the data from the two trial periods using a one-way ANOVA, also no significant differences were detected between 90 and 120 days. However, there was a significant difference (P = 0.0027) between the cover crops. Radish had significantly higher (P=0.0049) biomass compared to other cover crops, while Rye (P=0.0449) and Mustard (P=0.0056) had the lowest biomass, respectively. The most prominent weeds that were identified were cut-leaf primrose and corn spurry. Other weeds identified include cut leaf geranium, sedge, datilograss, and pigweed. The weeds data is under analysis. The second repeat of the cover crop study using the same treatments was established at the University of Georgia, Tifton campus in November 2021, and completed in April 2022. Data from the 2-year cover crop study will be analyzed and reported. In addition, UMass has prepared several Bt isolates for establishing the laboratory bioassays to evaluate their nematicidal effectiveness against the root-knot nematode.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Gitonga, D., Hamidi, N., and A. Hajihassani, A. 2021. Efficacy of certified bionematicides for control of Meloidogyne incognita in the greenhouse conditions. Journal of Nematology 53: 11. .
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Progress 09/01/20 to 08/31/21
Outputs
Target Audience:The target audience for this project isExtension agents and growers in Georgia and the neighboring states. However, the results will be used by extension specialists, county extension agents, crop consultants and professionals, and industry cooperators. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A Ph.D. student (Denis Gitonga) was hired from the proposal and is currently working on the project at the University of Georgia. In addition, three research technicians/biologists were able to assist in the preparation of Bt cry isolates and EPN metabolites at the UMass Medical School and USDA-ARS, Byron, GA, respectively. How have the results been disseminated to communities of interest?The greenhouse results on the efficacy of bionematicide products in the control of root-knot nematodes were presented as a poster at the annual meeting of the Society of Nematologists in Alabama in summer 2021. In addition, we plan to share the results with Extension agents and growers this winter at the 2022 Southeast Regional Fruit and Vegetable Conference in Savannah, GA, and at county grower meetings in GA. What do you plan to do during the next reporting period to accomplish the goals?Start or repeat studies to complete objectives 1 to 3, begin economics analysis, prepare manuscripts, and hopefully present studies at appropriate meetings.?
Impacts
What was accomplished under these goals?
Two independent greenhouse experiments were conducted to evaluate the nematicidal efficacy of eight commercially available products (Majestene, TerraNeem, AzaGuard, Molt-X, NemOmex, EcoWorks, Monterey, and Promax) against root-knot nematode (RKN), Meloidogyne incognita. After eight weeks, shoot length, shoot dry weight, fresh root weight, root gall severity using a scale of 0 to 5, and reproduction factor (Pf/Pi) were evaluated. There was no significant difference in the dry shoot weight and shoot length among all the treatments. AzaGuard and Majestene had the highest (P < 0.05) root weight, while Monterey had the lowest root weight compared to both control checks. Monterey had the lowest (P < 0.05) galling index, followed by AzaGuard and Molt-X compared to the positive control. However, Monterey had undesirable effects on the root system resulting in low galling severity and egg counts. The number of eggs per gram of root at the end of the experiments varied greatly and ranged from 1806 to 4815. Azaguard had the lowest (P < 0.05), while TerraNeem had the highest eggs per gram of roots compared to the positive control. AzaGuard outperformed all the other bio-nematicides and was selected along with a few other potential products for the field trials to manage Meloidogyne spp. in organic vegetables. A field study was conducted using cucumber in a certified organic field naturally infested with Meloidogyne spp., at the UGA Horticulture Hill Farms, Tifton, GA in April 2021. The trial utilized a randomized complete block design with seven treatments and five replicates. The experimental treatments used were: untreated control, AzaGuard, NemOmex, EcoWorks, Pendi, and Promax. RKN population was not significantly (P = 0.0933) affected by nematicide application. Despite a lack of statistically significant RKN reduction, Azaguard and Ecoworks were the best compared to other products. The root galling was significantly less (P = 0.033) on treated with Azaguard compared to other products including the untreated check. On the other hand, Pendi showed a significantly high galling index compared to other products but with control. Neither of the biological nematicides significantly (P=0.5806) affected the cucumber yield. However, numerically Ecoworks performed better compared to other treatments and the untreated check. Overall, the best two products were Ecoworks and Azaguard while the worst two were; Promax and Nemomex. This trial was repeated in July 2021, but the data were not included in this report due to time constraints. Another study was conducted in a certified organic field naturally infested with Meloidogyne spp., at the UGA Horticulture Hill Farms, Tifton, GA to determine the effect of different termination timing of cover crops on the development and population of nematodes and weed density. Winter cover crops were grown in the field in early November 2020 and terminated (harvested) 90 and 120 days after planting. Cover crop residues were then incorporated into the soil by a moldboard plow to achieve maximum allelopathic and/or nematicidal activity. Two weeks after incorporation, planting beds (false seedbeds) were prepared to stimulate weeds to germinate. Data collected included cover crop biomass accumulation, the abundance of plant-parasitic nematodes, root galling severity, and weed density. A significant difference (F = 2.885; P = 0.0116) in RKN populations was found between the interaction effects (Days in the field "90 & 120" and the cover crops) when analyzed using a two-way ANOVA. There was a significant (F = 4.1584; P = 0.0436) increase in RKN population when the cover crops were left longer (120 days) in the field compared to a shorter period (90 days), especially for radish. There were no significant differences (F = 0.4303; P = 0.8575) found between the interaction effects (before and after) cover crop incorporation in the soil trials (90 and 120 cover crops. When pooling and analyzing the data from the two trial periods using a one-way ANOVA, significant differences (F = 3.6971; P = 0.0021) were found among the treatments. Further analysis using the Tukey HSD test, Rye-Oat (P = 0.0062) had the lowest RKN population compared to other cover crops while Radish (P = 0.0006) had the highest population of RKN. Rye, Mustard and Oat did not differ significantly from one another, and neither were any significant differences between the three treatments and the fallow (with weeds and without weeds). No significant difference (F = 0.4835; P = 0.08196) in free-living nematode populations was found between the interaction effects (Days in the field "90 & 120" and the cover crops) when analyzed using a two-way ANOVA. Once pooling and analyzing the data from the two trial periods using a one-way ANOVA, significant differences (F = 4.8002; P = 0.0304) were found between 90 and 120 days. Generally, 90 days had more free-living nematodes compared to 120 days. There was a significant difference (F = 2.5793; P = 0.022) between the before and after incorporation of cover crops and the cover crops. Amongst all the cover crops, Rye, Radish and Mustard had a significant increase in the number of free-living nematodes after incorporation in the soil compared to before incorporation. No significant difference (F = 0.2428; P = 0.9123) in cover crop biomass was found between the interaction effects (Days in the field "90 & 120" and the cover crops) when analyzed using a two-way ANOVA. When pooling and analyzing the data from the two trial periods using a one-way ANOVA, also no significant differences (F = 2.8801; P = 0.0975) were detected between 90 and 120 days. However, there was significance difference (F = 4.8831; P = 0.0027) between the cover crops. Radish had significantly higher (P=0.0049) biomass compared to other cover crops, while Rye (P=0.0449) and Mustard (P=0.0056) had the lowest biomass, respectively. The most prominent weeds that were identified were cut-leaf primrose and corn spurry. Other weeds identified include cut leaf geranium, sedge, datilograss, and pigweed. The weeds data is under analysis.
Publications
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