NE1040: Plant-Parasitic Nematode Management as a Component of Sustainable Soil Health Programs in Horticultural and Field Crop Production Systems
(Multistate Research Project)
NE1040: Plant-Parasitic Nematode Management as a Component of Sustainable Soil Health Programs in Horticultural and Field Crop Production Systems
Duration: 10/01/2009 to 09/30/2016
Statement of Issues and Justification
The need. Plant-parasitic nematodes, most importantly the root-knot, lesion and dagger nematodes, continue to cause significant crop losses on important agronomic and horticultural crops grown in the northeastern United States. In many cases, these soilborne plant pathogens require implementation of varying management practices, often on an annual basis. Soil applications of chemical nematicides continue as the primary method for nematode management, especially on high value vegetable and fruit crops. Members of NE-1019, however, have made significant progress in identifying alternative nematode management options for fruits such as apples, peaches, strawberries, and vegetables including beans, carrots, onions, peppers, potatoes, tomatoes, and others, based on using nematode suppressive cover and rotational crops, biofumigants, resistant cultivars, and effective biological control agents, such as Pasteuria penetrans and P. thornei. In addition, the group has made progress in assessing the impact of selected cultural production practices on the diversity of nematode community structure at the trophic level and the polyspecific nature of nematode communities. The latter two aspects need significant additional research and integration into overall sustainable soil health management programs.
Intensive production of agronomic and horticultural crops in the northeastern region has resulted in a gradual deterioration of soil quality, thus contributing to reduced yield and profitability. It has also become obvious that increasing inputs and the intensity of production practices, such as tillage, are no longer effective in attaining and maintaining profitable crop yields. Causes of poor soil quality include: soil compaction, crusting, low organic matter content, increased pressure from plant pathogens, insects and weeds, and lower density and diversity of soil foodweb organisms (often referred to as beneficial soil organisms). Growers, extension educators and researchers now realize the need for the implementation of practical and sustainable soil management programs to improve soil productivity and farm profitability. This new concept of soil health deals with the integration and optimization of soil physical, chemical and biological factors for improved soil function (productivity) in an economically and environmentally compatible manner. Several multi-disciplinary soil health teams in the United States and abroad have been established to address soil health degradation issues and to develop holistic and long-term sustainable solutions. Significant progress has been made to date, including the development of cost-effective protocols for assessing the status of soil health, increasing soil health literacy, facilitating soil health demonstrations by growers, and promoting multi-disciplinary research and outreach. Although nematodes have been used as comprehensive biological models for all of science (Lee, 2002) and knowledge about plant-parasitic nematodes has recently been summarized by Perry and Moens (2006), relatively little is known about the relationships between soil health and management of plant-parasitic nematodes. There is an immediate need to assess the impact of soil health interventions on nematode community structure dynamics and integrate nematode control recommendations into soil health management programs designed for specific agronomic and horticultural production systems. The expansion of the soil health component of this project is, in part, in response to suggestions made by the Northeast Directors in their review of the previous project outline. Thus, we would like to propose that a new, five-year multistate project focus on developing biologically based nematode control practices that are not only compatible with overall soil health management practices, but are designed as integral components of these systems.
Importance of work and consequences if not done. United States consumers demand high quality, readily available and inexpensive food and fiber. For this to be achieved, in part, by northeastern producers of agronomic and horticultural crops, it is imperative that sustainable soil health systems be maintained, or in some cases, restored. Nematodes play three critical roles in this challenge: (i) the occurrence of high population densities of plant-parasitic nematodes results in low yields of poor quality produce, makes farming non-profitable and is a key component of poor quality soil; (ii) bacterial- and fungal-feeding nematodes are key components of soil food webs and are essential for optimal plant nutrition; and (iii) nematode community structure assessment has become recognized as an important tool for measuring soil quality. Northeastern farmers are very interested in plant-parasitic nematodes, the sustainability of soil health, soil quality restoration and having significantly improved nematode and soil management tools. Without the research and education programs associated with this proposed project, the economic viability and soil quality of the small, medium and large farms of the northeast region will continue to be at risk to unacceptable levels of degradation.
Technical feasibility of work. The following three items strongly defend the feasibility of the proposed work: 1) The progress made by the researchers associated with the current NE-1019 Multistate Research Project is a strong indication that plant-parasitic nematodes can be managed in a reliable manner with cultural controls based on host resistance, nematode antagonistic rotation or cover crops, soil amendments, and biological agents, 2) the roles of bacterial-and fungal-feeding nematodes in plant nutrition have been validated in several laboratories and technology has been developed for the use of nematode community structure assessment for analysis of soil quality, and 3) several members of the NE-1019 currently work closely with sustainable soil health management teams.
Advantages of a multistate effort. Northeastern agriculture and its associated polyspecific nematode communities offer challenges that are diverse and complex. Nematology, however, is only represented by a very small number of scientists. To achieve the objectives of this project, it is imperative for these individuals to work together as team members of a multistate research project. With current limited nematology personnel and resources, it would not be possible to achieve the objectives of this proposed project if pursued on an individual agricultural experiment station basis.
Impacts of work. The proposed multistate research project will: 1) enhance the economic viability of farms by saving costs associated with nematicide usage and 2) change the behaviors of farmers through extension and outreach to result in increased integrated management of nematodes, thereby increasing sustainable soil health of small, medium and large farms throughout the northeastern region. In addition, farmers will have an increased overall understanding about the nature of nematodes, the damage they can cause, and the key roles that these animals have in soil food webs. There will also be significant new knowledge added to the science of nematology.
Related, Current and Previous Work
A review of CRIS projects was performed and results are listed in Attachment C. A number of projects from outside the region had similar objectives but focus on different nematodes or crop systems. There are four other multistate regional nematology projects. Two focus on soybean cyst nematode, one involves issues of nematode management and trade and the final project deals primarily with host resistance. Our project has some overlap with the southern multistate effort dealing with host resistance (S-1015), inasmuch as both include plant resistance for nematode management, but the crops and target nematodes have relatively little overlap.
The loss of multi-purpose soil fumigants, such as methyl bromide, as well as several traditional nematicides from the market due to environmental concerns and the costs of re-registration has focused attention on the development of host resistance, nematode antagonistic rotation or cover crops, soil amendments and biological agents (Hirunslee et al., 1995; McSorley and Dickson, 1995; McSorley and Gallaher, 1992; Rodriguez-Kabana and Kloepper, 1998; Weaver et al., 1995).
The development and deployment of plant resistance to nematodes may be the single most effective means of managing these plant parasites. Plant resistance limits reproduction of the nematodes in the target crop and in some cases can be as effective as chemical control (Cook and Evans, 1987; Starr and Roberts, 2004). In one study of the economic benefits, the $1 million cost of developing a soybean cultivar resistant to cyst nematodes was far surpassed by $400 million in benefit (Brady and Duffy, 1982). The identification and development of plant resistance to nematodes will be investigated in SC (USDA); FL, NY and CT. Most resistance has been investigated against root-knot and cyst nematodes, and that will be the primary thrust in these efforts. However, strawberry plants selected for tolerance to lesion nematode-mediated black root rot will be evaluated for reaction to lesion nematode infection in CT.
Deployment strategies for utilizing resistance will also be investigated. RKN resistant vegetable cultivars as rotational crops may limit damage in subsequently planted susceptible crops. Cucumber and muskmelons double-cropped after a RKN resistant tomato produced increased yield, had reduced root-galling, and lower densities of M. incognita second-stage juveniles (J2) in soil than the same cucumber and muskmelon cultivars grown after a susceptible tomato (Colyer et al., 1998; Hannah et al., 1994; Hannah, 2000). The RKN resistant pepper Carolina Cayenne was effective as a rotation crop for managing M. incognita in susceptible bell peppers (Thies et al., 1998). Yield of squash grown in the spring following a rotation crop of castor, cotton, velvetbean, or crotalaria, produced heavier yields than squash grown after RKN susceptible peanut (McSorley et al., 1994). When eggplant was grown following resistant 'Mississippi Silver' southernpea, root galling by M. incognita race 1 was less severe than when eggplant was grown following susceptible 'Clemson Spineless' okra (McSorley and Dickson, 1995).
Crop rotation is a beneficial production practice and has been extensively studied as a more sustainable nematode and pathogen control measure than chemical pesticides. Crop rotations often reduce nematode populations by reducing reproductive potential and survival, eliminating or reducing population densities. Crop rotations and cover crops also can lead to disease reduction by increasing the population or activity of beneficial soil microflora. In such cases, the crop used in the rotation sequence is often selected for the development of a beneficial rhizosphere microbial community (Kloepper et al., 1991; Latour et al., 1996; Smith and Goodman, 1999; Weller et al., 2002). Among the organisms that are most likely favored by cover crops are fungal egg-parasites, nematode-trapping fungi, endoparasitic fungi, endomycorrhizal fungi, plant-health promoting rhizobacteria, and obligate bacterial parasites (Sikora, 1992). The use of legume cover or rotation crops provides organic nitrogen while also suppressing plant-parasitic nematodes. Unfortunately, many legumes are susceptible to RKN (Meloidogyne spp.), which is often the key nematode pathogens requiring management in many cropping systems (McSorley, 1998, 1999). A number of legume crops have been identified that are highly resistant to various species and/or races of RKN. Some of these, cowpea (Vigna unguiculata), velvetbean (Mucuna deeringiana), and sunn hemp (Crotalaria juncea) have potential in cropping systems (McSorley, 1999; Rodriguez-Kabana, et al., 1988, 1989; Sipes and Arakaki, 1997; Weaver et al., 1995). In addition to nematode management and nitrogen provided by nematode-resistant legumes, crop residues may increase levels of soil organic matter, improving water-holding capacity and other soil properties (McSorley and Gallaher, 1995).
Crop rotations can reduce certain nematode densities, but may increase populations of other nematode pathogens, particularly in polyspecific nematode communities (LaMondia and Halbrendt, 2003; Noe, 1998). Integration also must consider economic returns of rotation crops, additional capital and labor requirements, and grower and market acceptance of the rotation crop. In the northeastern region, rotations are already used as part of management programs for Globodera rostochiensis on potato (Brodie et al., 1993; Mai and Lownsberry, 1952), Heterodera schachtii on sugar beet (Mai and Abawi, 1980), M. hapla on carrot (Kotcon et al., 1985) and Xiphinema spp. on peach. Although crop rotation alone is unlikely to provide nematode management in all nematode-crop systems, their potential as a component of an integrated pest management system has not yet been fully realized. This potential, when integrated with other non-chemical management measures such as biological control, is likely to become increasingly important, as traditional nematicide options are lost. Several nematode-antagonistic crops including rotation and cover crops such as rapeseed, marigold, forage pearl millet, Avena strigosa, sudangrass and sorgho-sudangrass were identified in the current project (LaMondia and Halbrendt, 2003). Native prairie plants that are resistant to the northern RKN (LaMondia, 1996) may be useful as cover crops for managing this and other plant-parasitic nematode species. Various plant species may have differential effects on populations of each of these nematodes (LaMondia and Halbrendt, 2003). Furthermore, the incorporation of plant shoots as green manures appears to play a significant role in the nematode-antagonistic effects of these plants (Halbrendt, 1996; LaMondia and Halbrendt, 2003).
Biological control offers an alternative or supplemental management tactic to chemical or cultural control of plant-parasitic nematodes. Pasteuria spp. are obligate, mycelial, endospore forming bacterial parasites of endoparasitic nematodes, such as RKN (Meloidogyne spp.), and several ectoparasitic nematodes, such as lesion (Pratylenchus) sting nematodes (Belonolaimus) (Chen and Dickson, 1998; Giblin-Davis, 1990). These parasites are promising biological control agents for management of important agricultural species of Meloidogyne and Pratylenchus (Chen and Dickson, 1998). Pasteuria penetrans and Pasteuria thornei are widespread in soils in southeastern USA where RKN and lesion nematode populations occur. However, we know little about their occurrence or ability to cause soil suppressivenessmore northern latitudes. But we do know that Pasteuria occurs there because Wich and Dicklow (2001) reported Pasteuria-infected stunt nematodes from turf soil samples taken from Massachusetts.
We know that isolates of P. penetrans vary markedly in their specificity towards different RKN species and populations within species, however we know little regarding specificity of P. thornei. P. penetrans can reduce RKN populations below economic threshold levels in several different crops and environments (Chen and Dickson, 1998). More than 35 publications report that Pasteuria may reduce symptoms or disease severity caused by RKN in various crops (Chen and Dickson, 1998). In Florida, RKN and sting nematode suppression has been attributed to P. penetrans (Dickson et al., 1994; Chen et al., 1992; Weibelzahl-Fulton et al., 1996) and Candidatus Pasteuria usga, respectively (Giblin-Davis, 1990).
Pasteuria spp. forms endospores as their final growth phase and these spores are the infective stage that attaches to the cuticle. The ability to form spores is a significant advantage if we can formulate these bacteria for agricultural use because mature spores are highly resistant to drying and mechanical shearing. The relationship between soilborne Pasteuria endospores and suppression of infection of plants by Meloidogyne spp. has been well documented (Chen et al., 1997; Chen and Dickson, 1998; Weibelzahl-Fulton et al., 1996). The basis for biocontrol potential is due in part to the fact that propagation of the bacteria within the pseudocoel of the infected nematode host results in a loss of fecundity. The nematode host serves as a vehicle for multiplication of the infective endospores that are released in the soil to repeat a cycle of infection and multiplication (Preston et al., 2003). As the density of soilborne endospores of a particular species and strain of Pasteuria increases, those soils may become more suppressive to nematodes susceptible to infection by that species and biotypes of Pasteuria. Molecular probes have been developed with monoclonal antibodies and specific gene probes to quantify endospores in the soil and in planta (Schmidt et al., 2004; Schmidt et al., 2005). Selective gene sequencing for different lines of Pasteuria penetrans has SNPs used to distinguish lines on the basis of host preference (Nong et al., 2007). These approaches are now being applied to define the molecular basis of host preference and to explore the adaptation of lines different Pasteuria spp. for maximal virulence toward a specific nematode host. Special emphasis is needed on Pasteuria thornei in that this bacterium is reported to be specific to Pratylenchus spp., which is a main target pathogen for this regional project. Very little information is available on this bacterium regarding its specificity, host range, or adaptability to northeastern climates.
Other microbial pest control agents such as Arthrobotrys, Bacillus, Burkholderia, Hirsutella, Paecilomyces, Paenobacillus, and Pogona, may be used to enhance systems for the management of plant-parasitic nematodes (Kerry, 1998; Kokalis-Burelle et al., 2000; Sikora and Hoffmann-Hergarten, 1993; Siddiqui and Mahmood, 1996; 1999; Stirling, 1991). In addition, natural products from nematode-antagonistic microbes can be toxic to plant-parasitic nematodes or disrupt the nematode life cycle (Anke and Sterner, 1997; Anke et al., 1995; Chen et al., 2000; Hallman and Sikora, 1996; Han and Ehlers, 1999; Hu et al., 1999; Köpcke et al., 2001; Meyer et al., 2000; Singh et al., 1991). Active compounds that affect egg hatch and second-stage juvenile mobility of M. incognita and Heterodera glycines were identified from nematode-associated fungi and from rhizosphere-inhabiting bacteria and fungi (Nitao et al., 1999; Meyer et al., 2000; Meyer and Roberts, unpubl.). Two of these fungi, Fusarium equisetei and Chaetomium globosum, were used in bioassay-guided isolation to identify compounds responsible for in vitro activity against M. incognita (Nitao et al., 2001, 2002). Continued research is needed to identify additional microbes with ability to produce compounds active against plant-parasitic nematodes. These compounds have potential for application as novel nematicides, and as live biocontrol agents.
Many biologically based approaches to pest management employ organisms that are directly antagonistic to pathogens (Cook and Baker, 1983; Nemec et al., 1996). In addition to directly affecting pathogens, a second mode of action for microbial biocontrol agents is the stimulation of induced systemic resistance in the host plant that minimizes or prevents infection (Smith et al., 1999). The advantage of using a microorganism to induce resistance is that once the crop plant is colonized, the stimulating effect is continuous. The addition of microbial agents to transplant mixes provides an ideal delivery mechanism for introducing biocontrol agents on transplanted vegetable crops. Combinations of microbial agents, PGPR and elicitors can be conveniently introduced in this manner. Research indicates that several new species of Bacillus increase transplant vigor and yield in many different transplanted crops including tomato, pepper, and strawberry (Kokalis-Burelle et al., 2002a, 2002b; Kokalis-Burelle, 2003).
Cultural and biological approaches to nematode management may have numerous impacts on crop yield and sustainability beyond their impact on target plant-parasites. The success of cultural and biological control of plant-parasitic nematodes is usually evaluated based on the direct impact of management tactics on target nematode populations. However, the integration of crop rotations, cover crops, organic amendments, tillage practices, and other crop protection practices may have dramatic non-target effects on the physical, chemical and biological characteristics of soils. These non-target effects may substantially influence plant growth and yield. The concept of soil health uses certain characteristics such as low populations of plant disease and parasitic organisms, as well as high populations of organisms that promote plant growth, such as the majority of non-parasitic soil nematodes (Magdoff, 2001).
The issues of soil health and practices that preserve soil quality have become a major issue of concern in the last decade. But more than half a century ago, in1940, Sir Albert Howard stated that, "The maintenance of the fertility of the soil is the first condition of any permanent system of agriculture in the Industrial Revolution the processes of growth have been speeded up to produce the food and raw materials needed by the population and the factory. Nothing effective has been done to replace the loss of fertility involved in this vast increase in crop and animal production." More than 60 years later, the June 11, 2004 issue of Science was dedicated to soil and indicated that soil biology research is an imperative for the next frontier of science.
The basis for the concept of soil health was presented by Doran et al., 1994 in Defining Soil Quality for a Sustainable Environment and enhanced with Methods for Assessing Soil Quality (Doran and Jones, 1996), the Michigan State University publications on Production Ecology and Management (Cavigelli et al., 1998; 2000; Landis et al., 2002; Deming et al., 2007) and the Cornell University Soil Health Initiative. In general, these contributions defined a healthy soil as one with the ability to resist degradation and respond to management. Nematode community structure, water stable soil aggregates, soil carbon-nitrogen and particulate organic matter have been identified as among the key indicators of soil health. The Cornell University Soil Health Initiative developed a comprehensive protocol for soil health analysis.
The classic work of Ingham et al., 1985 demonstrated the significance of bacterial and fungal feeding nematodes and other soil fauna in nutrient mineralization. A set of mineralization partitioning coefficients was provided by Hunt et al., 1987. Inghams work was confirmed by Ferris et al., 1998 and Chen and Ferris, 2000. Ferris et al., 2001 published a comprehensive model for soil food web analysis based on the concept of structural and enrichment indices. Sanchez et al., 2001 reported on the relationships among carbon and nitrogen mineralization potentials, nitrate leaching, crop productivity and nematode community structure in MI cherry production. The Ferris et al., 2001 food web model was validated in 2004 for a California tomato production system (Ferris et al., 2001). Because nematodes colonize all trophic levels (Yeates et al., 1993), nematode community structure has become a widely recognized key indicator of soil and water quality and nematodes are used in assessment of atmospheric quality (Bongers, 1990; Bongers and Bongers, 1999; Bird et al., 2004; Ferris et al., 2004; Nehr, 2001). Bell et al., 2005 published a summary of the methodologies used for assessment of nematode community structure.
Recent studies suggest that cover-crop mixtures of legumes and grasses and soil water relationship enhancement technologies provide some of the most promising soil health enhancing technologies (Ferris et al., 2004; Nyiranza, 2003; Sanchez et al., 2001; Snapp and Borden, 2005; Smith, 2004). Impacts of these technologies have been shown to overwinter and improve the level of active, long-term soil organic matter pools and crop yields.
There are at least five trophic groups of nematodes in soils (Yeates et al., 1993). The change in nematode numbers, and nematode community analysis, has been successfully used as an indicator of soil health (Neher, 2001). Most soil nematodes are beneficial, having direct and indirect effects on soil nitrogen (Neher, 2001). The dynamics of nonparasitic nematode communities may be better predictors of soil health and crop sustainability than plant-parasitic nematodes. Cultural nematode management tactics such as rotation have been demonstrated to influence soil organic matter (Abawi and Widmer, 2000) and other physical, chemical and biological properties of soil. The number and diversity of free-living nematodes in soil reflect the availability of nutrients, water-holding capacity, soil structure, density, pH, buffering capacity and biological components (Widmer et al., 2002). Biological control tactics also may influence ecological characteristics of soils. Nematode community structure is likely influenced by a combination of previous soil use, soil factors, and initial species composition (Griffiths et al., 2002).
Develop effective and economically viable cultural management tactics for plant-parasitic nematodes based on host resistance, nematode antagonistic rotation or cover crops, soil amendments and biological agents.
Evaluate cultural management procedures for plant-parasitic nematodes in relation to their impacts on the sustainability of soil health: With special reference to the utility of nematode community structure as an indicator of overall soil quality and their roles in plant nutrient cycling.
Provide educational materials and programs on cultural management of plant-parasitic nematodes and sustainable soil health systems as a component of ongoing extension and outreach efforts.
MethodsObjective 1. Develop effective and economically viable cultural management tactics for plant-parasitic nematodes based on host resistance, nematode antagonistic rotation or cover crops, soil amendments and biological agents.
Scientists will search for resistance to Meloidogyne hapla in vegetable crops (onion and carrot, NY; and pepper, ARS-USDA - SC) and also to root-lesion nematode in vegetable (onion and beans, NY), small fruit (strawberries, CT), and rotational grain crops (rye, wheat, soybean, vetch; CT, PA, and NY). We (ARS-USDA - SC) have already evaluated more than 400 accessions of pepper (Capsicum spp.) from the U.S. Capsicum collection (USDA, ARS) and have identified a number of Plant Introductions (PI) with moderate resistance to M. hapla. Seed of this resistant PI is being increased for further testing against local isolates of M. hapla by collaborators in CT, MA, and NY. Work on the management of soybean cyst nematode on soybeans, sugar beet cyst nematode on sugar beets and stubby-root nematode on potato will be undertaken in MI. Resistant cultivars will be utilized to develop alternative nematode management strategies for managing root-knot nematodes in vegetable crops (ARS USDA - SC). The potential of using a resistant bell pepper and tomato cultivars as a rotation crop for managing M. incognita in subsequent, susceptible double-cropped cucurbits will be evaluated (FL). New rotational combinations of vegetable crops will be developed and tested for effectiveness in managing Meloidogyne spp. including double-cropping systems (susceptible vegetable crops after resistant cultivars). Appropriate herbicides will be applied in order to reduce weeds problems in all plots. Although the principles and concepts for managing plant-parasitic nematodes using resistant cultivars in rotation with susceptible cultivars are well established and proven, the usefulness of M. incognita resistant bell peppers and tomato as a rotation crop for managing this nematode in double-cropped cucumber and squash and eventually M. hapla-resistant crops in vegetable and small fruit systems has not been demonstrated. Furthermore, the effectiveness of resistant-susceptible vegetable cropping schemes for managing Meloidogyne spp. must be evaluated on a crop by crop basis because differences in levels of resistance and susceptibility of various crops (and cultivars) to various Meloidogyne species and races will affect their use. It is important to point out that other soilborne disease pathogens come in to play with such rotation schemes and must be considered.
The use of summer cover crops of RKN-resistant cowpea and sunn hemp for managing RKN in vegetable crops and the effects of these practices on soil microbial and nematode communities will be investigated by scientists in FL and SC (FL, ARS-USDA- SC, and ARS-USDA- FL). Field experiments will be conducted on sandy soils infested with M. incognita, a common nematode pathogen of many vegetable crops (McSorley, 1995). The leguminous cover crops 'Iron Clay' cowpea and sunn hemp, both which are suppressive to M. incognita (McSorley, 1999), will be evaluated in a split-plot design with three summer cover crops (sunn hemp, 'Iron Clay' cowpea, or none) as main plots and three amendment treatments (sunn hemp hay, cowpea hay, or none) as sub-plots replicated five times. The cover crops will be grown during the early summer on plots receiving cover crop treatments. The cover crop will be harvested before pod development to make maximum use of its value as a green manure. Cut residues of the cover crops will be removed from some plots or added to others depending on the treatment involved. Nematode-susceptible eggplant will be planted in the plots mid-August. Data will be collected on nematode population density, nematode community structure, disease incidence and severity, root damage (nematode galling and disease rating), crop yield, weed density, nutrient levels in crops and soil, soil organic matter, and soil water-holding capacity. The same cultivar will be evaluated and compared to resistant pepper for their ability to manage the northern root-knot nematode, M. hapla, in CT.
Scientists will assess the impact of nematode-antagonistic rotational or cover crops on populations of lesion and root-knot nematodes, and the impact of such antagonistic crops on nematode damage to vegetable crops in CT, PA, and NY. In NY, the mechanisms involved in such suppression will also be investigated. In the current project we have identified several nematode-antagonistic rotation and cover crops including rapeseed, marigold, forage and grain pearl millet, Rudbeckia hirta, sudangrass and sorgho-sudangrass. These crops will be further evaluated for nematode suppressiveness against RKN, cyst, lesion or dagger nematodes in parallel or complementary studies. No one plant was effective against all plant-parasitic nematodes in the Northeast. Some plants were more practical as rotation or cover crops due to agronomic traits, ability to compete with weeds (often hosts of the target nematodes) and ability to fit into cropping systems.
Native prairie plants with resistance to M. hapla (LaMondia, 1996) will be evaluated for host status to lesion and dagger nematodes. We have determined that different plant species may have differential effects on populations of lesion and dagger nematodes. Aster and Rudbeckia are resistant to M. hapla (LaMondia, 1997), and Rudbeckia and marigold reduced lesion nematode densities and potato early dying. The incorporation of plant shoots as green manures also may impact the nematode-antagonistic effects of these plants (Halbrendt, 1996; LaMondia and Halbrendt, 2003). CT and PA will evaluate seven grass species, four Aster species, purple and yellow coneflower, and small black-eyed Susan for their host status and effects as green manures on lesion and dagger nematodes, and for their potential as antagonistic cover and rotation crops. The antagonistic mechanisms of these plants, which reduce densities of plant-parasitic nematodes during plant growth or as a green manure, will be determined in the greenhouse, microplot, and field tests in CT, NY, and PA. The effect of several of these antagonistic crops on activity and population dynamics of soilborne biocontrol agents will be evaluated in WV.
The toxicity of root exudates or plant breakdown products such as glucosinolates released from Brassica residues (Sang et al., 1984) or the nematicidal residues from oats, sudangrass or sorgho-sudangrass will be evaluated in vitro or directly on nematodes in soil to determine the most efficacious use against particular nematode species. Brassica spp. are being grown or considered for production as oilseed feedstocks for biodiesel in the Northeast Region. Biofumigation with Brassica plant breakdown products has been successfully used as a green manure tactic against dagger nematodes in PA (unpubl.) but we have shown that lesion and root-knot nematodes can reproduce on plant roots over the season, even though they may be killed by the incorporation of plant residues. Brassica seed meals remaining after oil extraction may have high levels of glucosinolates and be portable, allowing application to target fields with nematode problems. Nematologists in CT, PA, NY, and SC will evaluate different Brassica spp. with different glucosinolate profiles and amounts against lesion, root-knot and dagger nematodes. Data and techniques developed in complementary systems have been shared to allow us to evaluate, compare, and increase efficacy of antagonistic plants on different nematodes. For example, the release of cyanogenic compounds and suppression of root-knot nematodes by sudangrass was increased when plants were incorporated prior to the first frost in NY. A low volume soil bioassay technique developed in PA is being used to further evaluate the toxicity of green or freeze-dried plant extracts on a variety of plant-parasitic nematodes using soils and nematodes supplied by cooperators in CT, MA, NY, and WV.
Researchers in TN will examine antagonism between plant species that produce aromatic compounds and plant-parasitic nematodes in the field, quantifying reduced nematode survival and reproduction. Experimental plants include monarda, epazote, and purple and yellow nutsedges. Extracts or whole plant amendments will be added to soil infested with M. incognita or M. hapla and planted with tomato or sunflower to determine the level of suppression. In other cases, test plants and susceptible hosts will be planted in pots to determine the antagonistic effect of the whole test plant on nematode survival and infection of the host plant.
Many beneficial microbes suppress plant-parasitic nematode populations. Research on these organisms is necessary to develop novel management agents. Microbes to be studied include species in the fungal genus Trichoderma and the bacterial genus Pseudomonas. Trichoderma isolates are available in commercial formulations for use against plant-pathogenic fungi and for enhancing plant growth. In addition, some Trichoderma isolates suppress populations of plant-parasitic nematodes in addition to other soilborne plant pathogens. For example, an isolate of Trichoderma virens was active against Pythium, Rhizoctonia, and Fusarium (Mao et al., 1997, 1998a, 1998b; Ristaino et al., 1994; Roberts et al., 2005), and produced culture filtrates that inhibited M. incognita egg hatch and J2 mobility (Meyer et al., 2000). When tested in the greenhouse for suppression of M. incognita on bell pepper, cucumber, and tomato, nematode populations on pepper were significantly reduced compared to controls (Meyer et al., 2000, 2001; Roberts et al., 2005). Continued research utilizing Trichoderma spp. will determine efficacy of selected isolates against plant-parasitic nematodes. Like Trichoderma, certain Pseudomonas spp. are active against soilborne pathogens, and commercial products are sold for suppressing pathogenic bacteria and fungi. Consequently, Pseudomonas isolates will also be tested against soilborne pathogens, including root-knot nematode, to determine efficacy as biobased management agents.
Pasteuria spp. will be selected for optimal virulence toward lesion and root-knot nematodes. Lines (biotypes) of Pasteuria penetrans have been isolated with preference for different races of M. arenaria, M. incognita, and M. javanica (Ostendorp et al., 1991; Chen and Dickson, 1998). The adaptive potential for improving the virulence of these lines toward different hosts will be determined. This will allow development of populations of endospores for suppression and biocontrol of these hosts. Significant progress made for the biocontrol of RKN will be extended to the biocontrol of species of lesion nematodes.
Objective 2. Evaluate cultural management procedures for plant-parasitic nematodes in relation to their impacts on the sustainability of soil health: with special reference to the utility of nematode community structure as an indicator of overall soil quality and their roles in plant nutrient cycling.
The soil health assessment methodologies will consist of comparative analyses of alternative management systems using methods that have consistently been shown to reflect nematode community structure, management activity, productivity potential, and the ability to hold nutrients and resist degradation. In addition to assessment of nematode community structure, using one or more or the seven procedures (Shannon-Weiner Diversity, Simpson Dominance, Species Richness, Nematode Channel Ratio, Maturity Index, Enrichment Index, Structure Index) described by Bell et al.,2005, other parameters such as monitoring water stable soil aggregates (Cambardella and Elliott, 1994), soil carbon-nitrogen (Bremner, 1965; Nyiraneza, 2003); and particulate organic matter (Cambardella and Elliott, 1992) will be included as appropriate for specific projects, especially those undertaken in WV, NY and MI.
Soil health change among alternative management systems will be measured at key long-term research sites such as the Cornell University Soil Health Initiative Research Site and the Michigan State University, Long-Term Ecological Research site at the Kellogg Biological Station. A soil health database will be established for the soil health assessment parameters and crop quality-productivity. Researchers in VT will undertake the first survey of nematode pathogens on vegetable crops and examine the free-living nematode communities in infested soils, estimate organic carbon, aggregate stability, and record management information in order to examine the relationships among these trophic groups.
The state of Tennessee has embarked on an ambitious biofuels program centered on switchgrass production. Nematode communities in switchgrass fields will be characterized for diversity and community composition. Several small research fields around the state will be sampled as well as new commercial fields. These communities will be compared to long-term natural stands in order to develop an understanding of the interactions of commercial switchgrass cultivation and nematode communities.
Objective 3. Provide educational materials and programs on cultural management of plant-parasitic nematodes and sustainable soil health systems as a component of ongoing extension and outreach efforts.
Results of research obtained under objectives 1 and 2 of this proposal will be shared and disseminated by the team members of this multi-state regional project to extension educators, IPM practitioners, private consultants, growers, and other agricultural service providers. There is a great need and interest in the implementation of sustainable management practices against plant-parasitic nematodes based on knowledge of host resistance, rotation and cover crops, and low-risk management products (Barker and Koenning, 1998). The recent interest and adoption of long-term and holistic soil health management program (Doran and Jones, 1996; Magdoff and van Es, 2000; Idowu et al., 2008) dictate that any developed nematode management options have to be compatible and a component of overall soil health management programs. The latter is indeed an appropriate strategy as all soil management practices (various modifications of tillage systems, rotation, cover cropping, and soil amendments) are known to drastically impact nematode population dynamics and their damage, especially on annual cropping systems. In addition, soil nematodes are also known to significantly contribute to several soil processes (decomposition of organic matter, nutrient cycling, biological control of other soil pests, etc.) as well as being used as indicators of soil function and health (Neher, 2001; Francis et al., 2006; Abawi and Widmer, 2000).
Members of this project and especially those with extension responsibilities (NY, MI, RI, MA, CT, PA, FL, VT) will provide a coordinated outreach in the region to promote a deeper understanding of the need to diagnose symptoms and sign of plant-parasitic nematode damage and the development and validation of nematode management practices. To facilitate integrating nematode management practices with overall soil health management, the planned outreach efforts will also provide detailed information on the emerging concept of soil health and appropriate long-term management practices. The project team members in MI and NY are already involved in presenting such activities ( http://soilhealth.cals.cornell.edu). In addition, all generated research and outreach information will be posted on the regional project web page with links to other nematode and soil health management web sites. Most importantly, several extension educators and growers will be collaborating with the regional project team members in conducting the proposed field trials, thus the direct outreach efforts. Furthermore, participating state members will be holding field days and hands-on training for diagnosing nematode damage, on-farm assessment of nematode soil infestations using simple and visual soil bioassays (Gugino, et al., 2008, Gugino et al., 2006), and discussion of available nematode management options. Finally, the results obtained will also be presented at commodity group meetings, field days, and annual extension meetings in each participating state as well as preparing extension bulletins, fact sheets, news paper articles, and scientific journal publications.
The impact of the delivered outreach efforts will be assessed through pre- and post-activity surveys (written, phone and/or face-to-face interviews), reduced nematode damage, reduced use of nematicides, management of nematodes on as needed basis (use of IPM strategies) and ultimately improved yield and profitability.
Measurement of Progress and Results
- Research on cultural management for plant-parasitic nematodes using resistant, non-host, or nematode-antagonistic rotation crops and green manures will increase our knowledge on nematode dynamics and damage, and will result in the publication of peer-reviewed journal articles and technical articles.
- Information will be developed about the efficacy of candidate biocontrol products.
- Development of Pasteuria spp. with enhanced virulence toward specific plant-parasitic nematodes will increase their efficacies for the biocontrol of their respective nematode hosts.
- Publication and distribution of extension publications on the host status of different cover and rotational crops to major nematodes and effects of soil management practices on nematodes and their damage.
- Nematode Community Composition patterns with different management and control efficacies.
- Identification of nematode-resistant cultivars of major crops or nematode-antagonistic cover crops for management of plant pathogenic nematodes.
Outcomes or Projected Impacts
- Knowledge generated during this project will lead to new components for integration into more effective nematode management systems and will help reduce losses in crop quality and yields. Growers will use new and improved methods for managing plant-pathogenic nematodes developed under this project that will reduce or eliminate the need for broad spectrum fumigants and other labeled nematicides lessening any potential harmful effects on the environment.
- Formalization of advisory programs for nematode management.
- Nematologists will be in a better position to advise agricultural stakeholders regarding the development and importance of plant-parasitic nematodes. This information can reduce the application of organophosphate and fumigant nematicides and lead to long-term health, environmental and food safety benefits due to reduced pesticide exposure.
- Training of onion, carrot, and other vegetable growers to conduct their own bioassays for root-knot nematodes will allow targeted nematode management only in fields with damaging nematode populations, thus reducing human health risk, environmental exposure, pesticide residues in food, and reduced production costs.
- Cover and rotational crops and green manures appropriate for each state's research efforts will be identified and screened against target nematodes.
- Continue screening of vegetable germplasm (carrot, onion, pepper, tomato) for resistance to Meloidogyne spp., including M. hapla and lesion nematodes, principally P. penetrans.
- Adequate sites for field trials with appropriate nematode population densities will be identified.
- Identify and define host-specificities of lines of Pasteuria spp. toward RKN and lesion nematode hosts.
- Brassica species and cultivars that differ in glucosinolate content and type will be grown, harvested and pressed to produce seed meals.
- Initiate collection of populations of Meloidogyne graminis and Subanguina radicicola and development of greenhouse maintenance system.
- Vermont plant-parasitic nematodes on vegetable surveyed.
- Characterize microbial enzyme products and free-living nematode community associated with increased level of soil suppressiveness to Heterodera glycines (Neher and Chen, in Minnesota, year 1)
- Hold educational sessions for stakeholders on diagnosing nematode damage and management options.
- Meloidogyne hapla-resistant pepper will be supplied to cooperators and tested against nematode populations in CT, NY and PA.
- Evaluate the effects of identified nonhost or antagonistic rotation crops against nematodes under field conditions.
- Brassica seed meals will be evaluated against lesion, root-knot and dagger nematodes using bioassays developed in PA.
- Evaluation of bentgrass varietal resistance to plant-parasitic nematodes.
- Develop lines of Pasteuria spp. with enhanced virulence toward specific RKN and lesion nematodes.
- Characterize microbial enzyme products and free-living nematode community associated with increased level of soil suppressiveness to Heterodera glycines (Neher and Chen, in Minnesota, year 2)
- Field evaluation of identified nematode-resistant vegetable cultivars.
- Continuation of outreach activities on nematode damage and management needs.
- Evaluate the effects of nonhost or antagonistic rotation crops against nematodes under field conditions - second year.
- Evaluation of identified resistant vegetable germplasm sources against root-knot and lesion nematodes under microplot and production filed conditions.
- Determine field activity in spring microplot trials and establish treatments for fall field trials for RKN control on tomato.
- Evaluation of bentgrass varietal resistance to plant-parasitic nematodes.
- Brassica seed meals will be evaluated against lesion, root-knot and dagger nematodes in field plots in CT, NY, PA and SC.
- Approach soil scientists from collaborating institutions and engage them in participating in lines of research focusing on microbial communities in soil.
- Characterize microbial enzyme products and free-living nematode community associated with increased level of soil suppressiveness to Heterodera glycines (Neher and Chen, in Minnesota, year 3)
- Hold field days and training sessions on plant-parasitic nematodes, soil health issues, and integrated management practices.
- Develop and validate integrated nematode management options based on results obtained on effective cover and rotational crops, biocontrol agents and resistant crop germplasm. Establish demonstration trials in experimental and production fields.
- Repeat field trials of Brassica seed meals against target nematodes.
- Evaluate the effectiveness of the established trials of soil management practices on nematode damage and assess their cost-benefits.
- Identify whether Brassica seed meals differed in efficacy against target nematodes.
- Continuation of outreach activities on nematode damage and management needs.
- Soil health meeting held
Projected ParticipationView Appendix E: Participation
The Multi-State Committee on biologically based alternative management systems for plant-parasitic nematodes will present programming in the participating states to its stakeholders including growers, commodity groups, agricultural industry representatives, extension educators, and homeowners. The Technical Committee will continue to sponsor a web page with project reports and links to other nematode management web sites. Participants from MA and RI have extensive extension responsibilities and operate nematode diagnostic laboratories that service numerous grower groups. These labs will utilize data generated from this project to make more precise nematode management recommendations to growers. Results obtained in this project will be presented at commodity group meetings and annual extension meetings and will also be published in extension bulletins, fact sheets, newspaper articles, and posted on web pages. In addition, field days for growers and extension educators will be held at the field trials sites as appropriate. Finally, several extension educators and growers will be collaborating in the field trials, thus the direct outreach effort.
The technical committee will consist of at least one voting member from each of the participating states (Attachment A), the administrative advisor, and the CSREES representative. Each year the technical committee will elect a chairperson, secretary, and at least one member-at-large to serve as an executive committee. The regional Technical committee will meet annually to report on the research results obtained, discuss and exchange information and ideas and to plan and coordinate next years work relating to the objectives of this proposal. A coordinator for each of the objectives may be designated to facilitate the coordination and reporting of the research being conducted by the collaborators. The technical committee may invite other scientists with experience in biological control, crop production systems, integrated pest management, sustainable agricultural practices, and others to participate in the annual meeting to provide specific information and strengthen the discussion.
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