Duration: 10/01/1999 to 09/30/2004

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Alfalfa is the principal forage component of a wide variety of agricultural production and conservation systems throughout the U.S. In 1997, 25 million acres of alfalfa were harvested with a conservative estimate of cash value of 10 billion dollars. This estimate does not include the value-added contribution of alfalfa to the ruminant livestock sector of the agricultural economy, for which 80% of nutrition resources come from forage like alfalfa, and with a value in 1997 of approximately 70 billion dollars. In addition, alfalfa contributes to the sustainability of rotational crop production systems because of its perennial nature and its ability to fix nitrogen. Alfalfa is grown m a variety of cropping systems, including both hay and grazing systems and as a monoculture or as an alfalfa/grass diculture. The varied cropping systems represent the reality of the diverse economic and ecological conditions that affect agronomic and pest management decisions.

The overall goal of the proposed regional research project is to address a critical concern of farmers: the significant reduction in alfalfa stand life caused by pests. Although alfalfa can persist in stands for many years, ecological and physiological factors act in concert with the pest community (e.g., weeds, pathogens, arthropods, nematodes) to shorten the life of stands The resulting lack of persistence significantly reduces profit and, in locations and periods of severe stress, effectively prevents profitable cultivation of alfalfa. The mission of the project is to improve persistence of forage alfalfa stands through the implementation of ecologically-based pest management.

Stresses imposed by such factors as unfavorable growing conditions, interference by weeds, and injury by pathogens, nematodes, and arthropod pests significantly shorten stand life. At times single factors such as a key pest species may threaten productive stand life but more typically loss of stands results from stresses imposed by several factors. Similarly, specific crop management practices affect not only the crop directly, but the interaction between pest populations and crop. Also, the nature of these effects must be studied from a regional or even national, perspective for a clear understanding. Thus, the complex issue of alfalfa persistence requires the input of a multidisciplinary and multistate team. As a result, this project will focus on an integrated and interdisciplinary approach to crop and pest management for improving stand longevity.

JUSTIFICATION: We have assembled a multidisciplinary research team with representation from 16 states to address key areas that will lead to improved alfalfa stand persistence. By focusing on the crop from physiological, organismal, and population perspectives, we plan to study complex interactions involving both biotic and abiotic factors, as well as crop management practices that impact alfalfa growth, survivorship, and demography. Clearly, a comprehensive, multistate effort is needed to address such broad areas of research. A Regional Project will provide base funding and an administrative structure to bring together a national team of researches to develop a framework for such studies, including the development of methods and the design of necessary experiments. With assurance of a five-year Project, we can leverage our activities with other short-term funding opportunities, such as the Regional IPM Grants Program National Research Initiative, or industry partnerships.

Although the emphasis of the Regional Research Project is on specific research objectives the scope includes the synthesis and implementation of crop and pest management strategies for diverse production systems. As a result, the project will be designed for participation by not only research scientists, but also extension specialists, crop consultants representatives from agribusiness, and farmers. The goal is to attain comprehensive input for planning, implementation, and evaluation. These groups will also be involved, as appropriate with planning and conducting of the research. This design assures effective implementation of the projects and the best possible acceptance of the outcomes by end-users.

A key feature of the project is enhanced communication of information across professional groups: e.g., research and extension specialists, crop and IPM consultants, agribusiness representatives, and farmers/decision-makers. A wide range of scientific disciplines will be represented: crop protection disciplines such as plant pathology, weed science and entomology; crop management disciplines such as agronomy, agricultural economics, soil science and meteorology. Mark McCaslin, President, Forage Genetics, has indicated a strong commitment to attend Project meetings and to maintain communication between public research and the private seed industry. Needs assessment, the implementation of programs, the delivery of existing information, and the generation of new information are all elements that will be integrated through communication.

The procedures for our objective-oriented research reflect three key elements of regional projects. First, we will conduct cooperative multistate research that involves shared protocols to achieve specific objectives. Second, discipline-oriented research will be conducted at individual states in a manner that provides knowledge adaptable to alfalfa production and pest management systems throughout the U.S. Third, to enhance effectiveness, we will use the project for a synthesis of data and ideas across disciplines and the public/private interface. We believe that all three elements are critical for improving the persistence of forage alfalfa stands.

Related, Current and Previous Work

Alfalfa pests and stand persistence. Agricultural scientists and producers alike recognize that forage alfalfa is affected by a wide variety of pests, including pathogens insects and weeds (Hanson et al. 1988). Pest management practices have focused on both single and multiple pest-crop interactions, however the time frame is generally limited to within a cutting cycle or production year. Yet, pests clearly impact the persistence2 of the stand as well, and alfalfa persistence is a major problem in managing pastures and hay fields (Marten et al. 1989; Chakraborty et al. 1996). Because of costs associated with planting, economic returns for forage crops are greatly enhanced by prolonging stand life (Moore and Nelson 1994). In addition, alfalfa persistence aids in sustainability and conservation of agroecosystems by reducing disruption of the soil environment, enhancing soil nitrogen levels, and providing refuge areas for natural enemies that can disperse into other crops. A number of pests have been associated with reduced forage legume persistence (Table 1). however other factors, such as mineral nutrition, harvest or grazing management, climatic factors, cultivars, and associated grasses, also influence stand decline.

Table 1. Pest complexes believed to contribute to the lack of forage alfalfa stand persistence in the central and eastern United States as identified by research and extension personnel within the project.

Pest complex	Specific casual groups	Examples
Competitive weeds	Warm and cool season Annual and perennial Grass and broadleaf	Bromus tectorum, Digitaria spp., Capsella bursa- pastoris, Lamium amplexicaule, Stellaria media, Cerastium spp., Setaria spp., Agropyron repens, Taraxacum officinale, Rumex spp.
Herbivorous insects	Root feeders Foliar and vascular feeders	Sitona hispidulus, Otiorhynchus ligustici. Hypera postica, Acyrthosiphon kondoi, Empoasca fabae
Root/crown diseases	Fungal pathogens Parasitic nematodes	Phytophthora medicaginis, Fusarium oxysporum, Aphanomycetes eutiches, Ditylenchus dipsaci, Meloidogyne hapla
Foliar/wilt diseases	Fungal pathogens Viral pathogens Bacterial pathogens	Verticillium albo-atrum, Psuedopeziza medicaginis, Phoma medicaginis, alfalfa mosaic virus, Clavibacter michiganense
Seedling diseases	Fungal pathogens Parasitic nematodes	Sclerotinia trifoliorum, Pythium spp., Aphanomycetes eutiches, Phytophthora megasperma, Meloidogyne hapla

Clearly, alfalfa persistence is a complex problem. The conclusion of an interdisciplinary symposium (Beuselinck et al. 1994) on the subject states the solution best: "We must strive to understand legume persistence at all levels; genetic, biochemical, physiological, ecological, and economic. Cause-effect relationships must be determined, and information obtained must be incorporated into legume improvement programs." Thus, a major challenge facing the sustainability of alfalfa production systems is the long-term impact of pests on stand persistence, the focus of the proposed regional project.

That unacceptable rates of stand decline exist is well-documented, yet the mechanisms and interactions of pest and crop management factors are not fully understood. As listed in Table 1, various pest complexes attack crops and result in reduced plant density and vigor with time. Detailed specific examples are beyond the scope of this proposal, and have been the subject of considerable emphasis in the past (see Marten et al. 1989 for examples). However, detailed studies that integrate factors of stand persistence are few. For example, Berberet et al. (1987) found that alfalfa persistence was especially reduced under the combined pressure of alfalfa weevil defoliation and interference from cool-season grasses. In part, the combined effect resulted from foliar feeding by alfalfa weevil that increased light penetration into the alfalfa canopy, allowing increased weed growth and interference. Contributors to reduced persistence, then, includes both types of pests working in concert. In a similar example, a study of fungal crown and root rots concluded that the reduction of pest-induced losses will rely on concomitant control of clover root curculio and fungi that cause crown and root rot (Kalb et al. 1994). Forage researchers expect that even more complex interactions contribute to the lack of alfalfa persistence.

Alfalfa physiology and the impact of pests on stand persistence. Uninjured alfalfa plants undergo profound physiological changes through the cycle of shoot initiation, vegetative growth, and reproductive development between defoliations. Photosynthesis and dinitrogen fixation are processes which supply carbohydrate and nitrogen compounds required by alfalfa. However, phloem tissue provides the transport mechanism for constituents necessary for each step of the cycle. In addition, root and crown tissues play critical roles as storage organs for organic reserves. These storage tissues enable alfalfa to survive complete defoliation, and allow the plant to survive during winter weather. Thus, since pests can interfere with a wide range of physiological functions, the injuries they cause may result in stresses that reduce stand persistence.

The role of nonstructural carbohydrates in regrowth and persistence has been studied extensively. In a classic study, Graber et al. (1927) reported that nonstructural carbohydrate concentrations in alfalfa roots declined in spring as plants resumed growth and also after defoliation. The concept of reserve carbohydrates, more than any other single concept, has driven alfalfa management decisions. Briefly, concentrations of carbohydrates decline rapidly in alfalfa roots during the 10-d immediately after defoliation as new shoots begin development (Smith 1962). A portion of the carbon made available by degradation of root starch is used for shoot growth, while part is used to maintain roots and crowns (Rapoport and Travis 1984, Pearce et al. 1969; Smith and Silva 1969). Carbohydrate concentrations remain low between Days 10 and 20 post-defoliation, after which root carbohydrates reaccumulate as photo assimilate production exceeds that required for shoot growth. Plants whose reaccumulation of root carbohydrates is limited by pest-induced stress may have reduced growth rates following the next defoliation, or worse, may fail to survive.

However, recent evidence suggests that proteins, not carbohydrates, are especially important for legume survival and regrowth subsequent to defoliation (Volenec et al. 1996). A growing number of studies have critically evaluated the role of taproot proteins in regrowth stress tolerance of alfalfa. For example, Vance et al. (1979) reported that dinitrogen fixation of alfalfa declined 88% within 24 h following defoliation and remained low for 13 days. Early regrowth, comprised largely of N-rich leaves (Etzel et al. 1988), precedes recovery of dinitrogen fixation (Vance et al. 1979; Cralle and Heichel 1981). Addition of Nas nitrate immediately after defoliation has no effect on herbage regrowth rate (Vance and Heichel 1981). These authors suggested that N remobilization from nodules and from storage pools in roots must be sufficient to meet the N needs of regrowing shoots until nodule function is restored. Alfalfa roots accumulate substantial quantities of N as protein and amino acids. Relative abundance of these N pools declines when shoot growth is initiated in spring and when herbage regrowth occurs after defoliation (Volenec et al. 1991; Hendershot and Volenec 1993a, b). Because they comprise up to one-third of the buffer-soluble protein pool and appear to be preferentially mobilized from roots to regrowing shoots, they have been characterized as vegetative storage proteins (VSP) (Cunningham and Volenec 1996).

With this new information on the physiology of alfalfa and its biochemical mechanisms to survive the stresses of defoliation and winter conditions, there is a need to study the impact of pests on VSP accumulation and subsequent use in shoot regrowth. For example, because of its potential to disrupt vascular tissues (Nielsen et al. 1990), potato leafhopper injury may significantly influence synthesis, accumulation of VSPs in alfalfa roots, and subsequent VSP use in shoot regrowth after defoliation. While previous hypotheses dealing with the impact of sap- feeding insects on alfalfa physiology have included concepts involving root carbohydrates, recent evidence (Avice et al. 1996, Barber et al. 1996, Volenec et al. 1996) suggests that root VSPs may be crucial for shoot regrowth and persistence of alfalfa. Therefore, it is imperative that we revisit the Smith regrowth process and ascertain the impact of pest injury on both C and N reserve levels.

Alfalfa yield components and the impact of pest stress on stand persistence. Our understanding of the physiological responses of plants (including alfalfa) to pest injury remains rudimentary (Pedigo et al. 1986, Higley and Pedigo 1997). Insofar as plant-insect interactions are concerned, we understand how plants influence insects - ecologically, behaviorally, and physiologically - but lack knowledge of comparable effects of insects on plants. Although basic information on physiological effects of common injuries, such as defoliation, has improved in recent years, substantial gaps exist in our understanding of how insects, pathogens, and weeds affect plant productivity and fitness, including persistence of perennial plants like alfalfa.

Considerable research has focused on reduction of crop productivity because of damage by pests without considering the mechanisms involved in these reductions (Poston et al. 1983). The absence of broad explanations, or even hypotheses, regarding effects of specific types of insect injury on alfalfa physiology requires that effects on production be tested separately for every injurious species. Many authors have advocated more studies addressing the effects of arthropod injury on such physiological parameters as photosynthesis, transpiration, phenology, growth form, and reproductive potential (Bardner and Fletcher 1974, Boote 1981, Higgins et al.1984, Ordish and Dufour 1969, Pedigo et al. 1981, Higley and Pedigo 1997). Work in these areas would represent the foundation for broader considerations of biotic stressors on alfalfa and for developing general hypotheses that predict specific physiological responses of other plants to various types of injury. More specifically, such studies would provide the basis for developing decision indices for multiple pests (Poston et al. 1983, Pedigo et al. 1986). Additionally, delineating injury-induced changes in host physiology is fundamental to explaining interactions between stressors, and the lack of such an understanding has been an impediment to the development of realistic simulation models for interactions between alfalfa and biotic stressors. Ultimately, our ability to efficiently reduce losses in alfalfa from biological stressors will be constrained as long as we cannot characterize the physiological mechanisms behind these stresses.

Through previous research, progress has been made in quantifying the combined effects of several pest species, but this work demonstrates the need to quantify more than the reduction in biomass of the crop. To fully understand the impact of biotic stressors on alfalfa persistence, the crop must be viewed as the integrative entity and the effect of pests on the physiology of the crop must be quantified. Therefore, physiological effects on biotic stress to alfalfa are emphasized in this proposal as a common language to understand the impact of individual and multiple stressors.

We have chosen to conceptualize alfalfa persistence by focusing on yield component analysis (Volenec et al. 1987). Herbage yield per unit area is equal to 1) the density of plants per unit area times 2) the number of shoots per plant times 3) the mass per shoot. As an alfalfa stand ages under minimal stress, there is a natural sequence in the three yield component parameters. The density of plants, dependent on seeding rate, is high and falls rapidly during the first (establishment) year. Subsequently, the density falls at a constant percentage rate. In contrast, the number of shoots per plant increases each year, compensating for plant death. The shoot mass generally remains constant with age. Using this approach, we can identify key characteristics to maximize yield and persistence of a stand (Volenec in press).

Pest complexes vary in their impacts on yield components, and thus have different effects on the persistence problem. For example, potato leafhopper injury to shoot tissue reduces translocation of photoassimilates toward crown and root storage tissues (Lamp unpub. data), thus potentially limiting the maximum numbers of shoots produced by plants during the next growth cycle. Pathogens, nematodes, and insects that injure crowns and roots may impact plant survivorship in severe cases, or impact shoot production or shoot mass in other cases (Beuselinck et al. 1994, Boelter et al. 1985). Weeds likely reduce light or water interception by alfalfa, thus reducing shoot mass, or subsequently, shoot density. By measuring the impact of individual and combined stresses on alfalfa yield components through time, we intend to determine key management points to improve persistence.

Pest management and stand persistence. Integrated pest management (IPM) is a system of pest control that seeks to manage pests using economically efficient and environmentally sound approaches (Cate and Hinckle 1994; Bottrell 1979). It relies primarily on preventive approaches, such as host plant resistance, biological control, and cultural practices, to maintain pest populations and their injury below damaging levels. If preventive approaches fail, then responsive practices, such as the application of pesticides, are used on the basis of pest densities or disease incidence and the comparison to established economic thresholds. In recent years, new terms that are essentially the same as IPM have developed, e.g. biologically intensive integrated pest management (Frisbee and Smith 1989), biologically-based pest management (U.S. Congress 1995), ecologically-based pest management (National Research Council 1996), and total system approach to sustainable pest management (Lewis et al. 1997). The new terms place even more emphasis on sustainable approaches for pest control, with the goal "to restore and preserve balance to the managed ecosystem by duplicating natural processes to the maximum extent possible" (National Research Council 1996, p. 115). By focusing on host plant resistance, biological control, and cultural control, the regional research proposed herein embraces those philosophies and extends them to the problem of alfalfa persistence.

Development of host resistance to potato leafhopper has been a difficult process and illustrates the need for public-private cooperation and regional research. Public researchers first spent considerable effort attempting to identify insect resistance within domestic alfalfa germplasm. In the mid 1970's, researchers turned their attention to wild relatives of alfalfa gathered from several areas of the world and present in the plant introduction collection. Several Medicago species having erect glandular hairs on the stems and leaves were identified which exhibited improved resistance to several insect pests of alfalfa, including potato leafhopper (Horber et al. 1981, Shade et al. 1979). This germplasm was developed by scientists at several institutions, most notably Purdue University, Kansas State University, and USDA.

Beginning in 1985, glandular-haired germplasm was released to the private breeding industry, but the material lacked adaptation and resistance to many common alfalfa pathogens. Furthermore, it was characterized by slow recovery after cutting and the percentage of leafhopper-resistant plants in the released populations was relatively low (McCaslin 1994, Shade 1996). Several industry breeding programs began the challenging process of incorporating the glandular-haired trait into agronomically acceptable varieties while striving to increase the level of resistance. Commercial seed of several glandular-haired alfalfa varieties became available for the first time in 1996-97. To date, the glandular-haired alfalfa germplasm has exhibited the greatest gains in leafhopper resistance; however, other germplasm sources may be useful in providing leafhopper resistance genes in the future.

Similar preventive approaches are being developed for many insect, pathogen, nematode and weed pests of alfalfa. Our goal is to optimize the development of various pest management tactics through a regional, multistate effort, and in particular to develop a general, multidisciplinary strategy for managing all alfalfa pests with the goal of improving stand persistence.

Objectives

1. To elucidate mechanisms by which biotic agents interact with abiotic factors to limit stand persistence of forage alfalfa.
   
2. To enhance alfalfa persistence through improved plant resistance to key pests by conventional breeding and genetic engineering approaches.
   
3. To identify and enhance biologica1 and cultura1 control measures that reduce pest populations and improve forage alfalfa persistence.
   
4. To integrate control measures with decision-making guidelines for adoption by specific states/regions.
   
5. 
   

Methods

A common procedure through all our objectives is the measurement of alfalfa stand persistence as impacted by various abiotic and biotic factors, as well as by crop and pest management practices. The common procedure will be critical to compare and contrast the role of factors and practices within our understanding of the life of an alfalfa stand. Therefore, a major goal during our first project year is the development of a standardized protocol for measuring stand persistence. This protocol will include the separate measurement of each of the alfalfa yield components: number of plants per unit area, number of shoots per plant and the herbage yield of shoots. Based on discussions, two such standardized samples are planned to be collected within field plots each year. In this way, various stresses can be compared to each other in common terms, specific mechanisms for the loss of persistence can be identified and management practices can be modified to improve persistence.

1. To elucidate mechanisms by which biotic agents interact with abiotic factors to limit stand persistence of forage alfalfa.

Research planned under this objective is grouped into three subobjectives:

A. Multivariate analysis of abiotic conditions, pest densities and alfalfa stand conditions. Individual states will collaborate to assess broad patterns relating pest and disease organism populations abiotic environmental factors, management practices, and alfalfa stand persistence under actual production conditions. States contributing to this data set include Illinois, Kentucky, Maryland, Michigan, Missouri, Nebraska, Ohio, Oklahoma. South Dakota, Wisconsin, and Wyoming.

Participants will collect data to include in a multivariate data set in which each observation consists of variables characterizing a single alfalfa field. Number of fields sampled within states will vary between 5 and 15 during each year. Observations will include variables falling into four broad subsets: abiotic environmental factors (e.g. soil texture bulk density, organic matter content), biotic factors (e.g. weeds, insect pests, disease severity) management factors (e.g. variety, rotation, tillage, fertility, cutting frequency and timing, grazing, and variables relating to stand persistence (e.g. crown density, shoot density). Characterizing the persistence of alfalfa stands will require repeated measurements through time, beginning with establishment and continuing for several years. Specific variables to be measured and methods to be used will be developed jointly by consensus of the participants so that observations between all participating states are standardized and comparable. Where appropriate, samples collected by participants will be forwarded to a single lab for analysis to ensure consistency.

Multivariate statistical techniques will be used with subsets of the data to investigate specific a priori questions. For example, biotic and abiotic environmental variables will be analyzed using canonical correlation analysis or canonical correspondence analysis to determine whether populations of pest organisms occur independently or are intercorrelated, and whether such pest complexes are related to underlying abiotic environmental conditions. The revelation of such patterns would be helpful in identifying risk factors for the occurrence of pests thought to affect stand persistence, and may suggest cause and effect relationships. Other methods that may be used include principle components analysis, multiple regression, multidimensional scaling analysis of similarities and cluster analysis.

B. Identify and characterize changes in physiology, biochemistry, and gene expression associated with pest injury. Indiana will characterize changes in the physiology, biochemistry and gene expression of alfalfa that occurs as a result of biotic stresses. Starches, sugars, nitrogen pools (amino acids, protein concentration and composition) will be measured in roots and crown buds exposed to stress. The goal is to elucidate how successful plants survive the stress. Furthermore, they will isolate genes expressed in surviving germplasms and characterize their function.

Individual states will collaborate with Indiana to examine the impact of specific stresses. For example Maryland will investigate the impact of the phloem-disrupting potato leafhopper on the storage physiology of alfalfa. In addition, they will perform experiments to determine the impact of leafhopper injury on phloem translocation and patterns of photosynthesis within injured plants. Furthermore, Nebraska and Maryland will collaborate on the interaction of leafhopper injury, water stress, and alfalfa physiology.

Establishment of a current national database on alfalfa persistence and factors affecting stand longevity. Kentucky will lead an effort (with all other states cooperating) to develop and conduct a survey. Each Forage Extension Specialist and other selected alfalfa leaders will be surveyed to ascertain average life stand of alfalfa, as well as their perception of biotic and abiotic factors affecting stand longevity. Every effort will be made to receive a response from each state. The survey will be used to identify research and education needs. In addition, the survey will be repeated at the end of the project to determine project effectiveness.

2. To enhance alfalfa persistence through improved plant resistance to key pests by conventional breeding and genetic engineering approaches. The key to the high productivity of alfalfa over a wide range of conditions has been the extensive breeding programs by private and public scientists. The continued cooperation of these entities is considered critical for optimum development of new cultivars through identification of mechanisms, evaluation under a wide range of conditions, and implementation in cooperation with extension programs. Of particular concern to this project is the persistence of alfalfa stands and each state participating intends to collect persistence data as part of standard evaluation trials. Through a regional effort, evaluations will be conducted in a wide range of climatic conditions, thus providing stronger evidence for the relationship between alfalfa genotype and persistence.

One of the critical stages for stand persistence is during stand establishment. Missouri and Pennsylvania will evaluate the effect of seeding rate on weed control and the plant thinning process. Selected varieties will be planted in spring at different seeding rates, with evaluations of seedling mortality during the first month, until the first harvest at about 80 days after planting, and again in the fall after the last harvest. Stand density and stems per plant will be followed through the seeding and subsequent years. Weed invasion will be monitored. These data will help understand the rationale for recommendations on seeding rate to enhance persistence.

Kentucky and Ohio will investigate the impact of Sclerotinia crown and stem rot on seedling establishment. To assess resistance, selected entries of alfalfa will be planted in early September in a replicated trial into sites where Sclerotinia trifoliorum was previously allowed to develop high levels of inoculum. Stand density and yield will be assessed during the following spring and summer. Plant size will be assessed at the end of each trial, and "plant digs" will be conducted to provide commercial breeders the opportunity to select plants that survive epidemics. Missouri will also monitor older stands for sclerotinia infection and plant death.

Similar evaluations will be conducted on infestations of seedlings by blue alfalfa aphid in Oklahoma, leading to improved resistance in semi-dormant alfalfa germplasm. All potential sources of resistance to the virulent strain of blue alfalfa aphid described in Oklahoma will be evaluated and resistance will be enhanced as much as possible by conventional breeding approaches. In addition, researchers in Oklahoma will cooperate with plant breeders in the private sector to evaluate products of their cultivar development efforts. These studies involve greenhouse evaluations of germplasm as well as field experiments to assess pest resistance and alfalfa productivity.

The availability of glyphosate resistant alfalfa seed, expected soon, will provide an opportunity to test for the effect of weeds on persistence. Wisconsin, Illinois, Missouri, and Michigan will perform field tests of this germplasm to measure weed population development and impact on each of the alfalfa yield components. Impact of winter annual, summer annual, and perennial weed species will be determined through factorial experiments. Other states will use glyphosate resistant alfalfa in field studies to measure the impact of weeds in combination with other pest factors.

The evaluation of glandular-haired cultivars with resistance to potato leafhopper will continue as began in the regional project NC-193. Ohio, Kentucky, Wisconsin, Missouri, Michigan, Minnesota, Pennsylvania, Virginia, Indiana, and Maryland will conduct studies on new alfalfa cultivars as they are released. The field studies will include replicated experiments of resistant and susceptible cultivars, with and without insecticides, to compare leafhopper densities and alfalfa yield, quality, and persistence. In a related study, South Dakota will evaluate the stem anatomy of glandular-haired and Medicago falcata alfalfas.

New York will focus on screening for improved resistance to diseases and snout beetle through existing collaboration with an existing breeding program. These pests are especially reducing alfalfa persistence in specific regions in New York. New selections will be farther tested against clover root curculio by Pennsylvania and other states. Wyoming will screen for resistance to brown root rot caused by Phoma sclerotioides through collaboration with an existing breeding program Experimental lines derived from field selections will be evaluated in the field where the fungus is known to occur.

3. To identify and enhance biological and cultural control measures that reduce pest populations and improve forage alfalfa persistence.

Certain pests are known to influence stand persistence and will be the focus of specific research toward the development of biological control. For example, Pennsylvania and New York will take the lead in developing biological control agents for clover root curculio Sitona hispidulus and alfalfa snout beetle, Otiorhynchus ligustici. An entomophagous nematode, Heteororhabditis bacteriophora (Oswego), persists well in alfalfa fields and shows potential for reducing clover root curculio injury. If current studies indicate further promise, other states, including Kentucky and Wisconsin, will test the effectiveness of the nematode. In addition, geographic populations of Microcotonus aethiopoides show different preferences for Sitona and Hypera weevils. Research is planned to investigate potential populations that would attack clover root curculio and alfalfa snout beetle.

Minnesota and Wisconsin will continue their effort to introduce and establish the parasitoid Dacnusa dryas, for biological control of alfalfa blotch leafminer, a recently introduced pest in the upper midwest (including North Dakota, Minnesota, Wisconsin and Illinois). Early studies indicate that most commercial alfalfa cultivars do not provide adequate resistance or tolerance to alfalfa blotch leafminer, and that most insecticides are also not that effective. Thus, the best long- and short-term management option appears to be biological control. D. dryas has been very effective in the northeastern U.S. and Ontario, Canada.

In general, natural enemies are expected to add to the persistence of alfalfa through the prevention of pest outbreaks. Yet, certain management practices may influence natural enemy densities. For example, several states are concerned about the impact of the new glandular haired alfalfa cultivars on natural enemies. Virginia will conduct a field study comparing the response of natural enemies of alfalfa weevil to a glandular-haired alfalfa cultivar and a leafhopper-susceptible cultivar. Weevil larvae and adults will be collected, and parasitization by natural enemies determined by dissection. In a similar design, Maryland will determine the effect of glandular-haired alfalfa on Anagrus nigriventris, the primary natural enemy of potato leafhopper. South Dakota will conduct a study comparing the densities of alfalfa weevil and its natural enemies among the use of several cultivars and management tools. Finally in Oklahoma, studies will be conducted on interactions of beneficial species (hymenopteran parasites and pathogenic fungi) which attack alfalfa weevil and aphid species. The relative efficacy of each species will be assessed under a variety of field conditions to include varied cutting and grazing schedules, pure alfalfa and alfalfa-grass mixtures, and irrigation on the prevalence of infections by entomopathogenic fungi.

Pest populations may be modified by manipulating cultural practices, and several states plan studies to observe pest responses to standard agronomic practices. For example, Nebraska, Illinois, Missouri, and Oklahoma will conduct a series of investigations on the effect of grazing/harvest management on alfalfa persistence. The influence of varying schedules on yield and stand longevity will be determined. Interactions with pests will be determined by monitoring insect, disease, nematode, and weed densities within each study, and by conducting specific experiments integrating pest management and grazing management of alfalfa crop systems.

Mixing forage crop species may provide protection of alfalfa from pests. Several states plan to investigate the impact of mixing crop species on individual pest species and on alfalfa growth and persistence. South Dakota will investigate the intercropping of cicer milkvetch and alfalfa. Maryland, Missouri and Pennsylvania will investigate the intercropping of orchardgrass and alfalfa, especially with regard to clover root curculio densities. Wyoming will evaluate intercropping forage grasses and alfalfa as a control for brown root rot. Field experiments will include monocultures of each crop species and at least one intercropping treatment. Insect, weed, and pathogen pests will be determined within replicated plots.

Soil fertility is another primary cultural practice that affects alfalfa stand production and stand persistence. Yet, fertility also impact various pests, either positively or negatively. Individual states will conduct experiments relating to the pest response to soil fertility and/or cutting management. In Kentucky, Missouri, and Oklahoma, soil fertility levels will be related to the extent of weed interference in alfalfa.

4.To integrate control measures with decision-making guidelines for adoption by specific states/regions.

This objective includes a multiple-stage process of 1) research studies designed to identify combinations of production practices and pest management strategies that are compatible and have merit in improving productivity of alfalfa stands, 2) on-farm demonstrations of integrated approaches managed as a combined effort of researchers, extension specialists, and producers, and 3) development of a conceptual model for alfalfa management and its modification to the needs of specific regions and/or states through collaboration. Oklahoma, Kentucky, South Dakota, Ohio, Missouri, Michigan, Maryland, Nebraska, Virginia, and Wyoming will participate in these studies.

The research studies for stage one will consist of field plots that compare alfalfa productivity and persistence using comprehensive management systems. Designs will vary by state and/or region, but will include manipulations of key management practices that impact pest densities, yield, quality, and persistence. The goal is to test specific combinations of management practices that are believed to optimize alfalfa production through carefully controlled experimentation before these are demonstrated on-farm. Pest densities will be monitored using standard scouting techniques. Yield and quality will be assessed by sampling a subplot within each plot with a forage harvester. Persistence will be measured using the standardized protocol described above.

In the second stage, demonstrations will be conducted in large plot, unreplicated areas on private farms. Specific practices will be evaluated that are of interest to the producers who host the studies. Producers will participate in data collection and dissemination of information through the demonstrations. The value of various management options will be determined with detailed analyses of inputs, yields, and stand ages to develop guidelines for the most profitable management decisions in alfalfa production.

In the third stage, information gained from extensive research and extension experience, including objective 1-3 and stages 1 and 2 above, will be conceptualized for discussions, identification of research needs, and applications for specific regions and/or states. A web site has already been established for this purpose (http://persist.umd.edu), and annual meetings will also address the progress of the conceptual model. The model will initially adopt the Alfalfa Calendar, developed at Oklahoma State University, for organization of both agronomic and pest management practices. The calendar will address both long-term concerns such as crop rotations to immediate advisories requiring rapid decision-making. As the conceptual model is developed individual states will modify it for their own conditions and place it on their web sites.

Measurement of Progress and Results

Outputs

• See attached "Expected Outcomes"
• empty

Outcomes or Projected Impacts

Milestones

(0):0

Projected Participation

View Appendix E: Participation

Outreach Plan

Organization/Governance

The organization and conduct of this project will be in accordance with procedures in the Manual of Procedures for Cooperative Regional Research, CSRS-00-1082, Revised 1980.

The regional technical committee will be responsible for the planning and research in the approved project and for coordinating research activities of the cooperating stations.

The officers elected will be a chair, vice-chair and secretary. The executive committee will consist of these officers. A coordinator actively involved in the research will be designated for each project objective (see below). The chair, with the assistance of these coordinators will be responsible for preparing annual and final reports. Each participating state will have a designated voting member who serves as the project leader for that state.

The chair, in consultation with the administrative advisor, will notify the technical committee of the time and place of the annual meeting, prepare the agenda, and preside over the meetings and the executive committee. The secretary will record and distribute the minutes. In the absence of the chair, the vice-chair will assume the chair's responsibilities. The executive committee will conduct any business of the committee between meetings. Subcommittees may be appointed by the chair for specific assignments.

Research within objectives will be integrated through objective coordinators to be identified at the first meeting. Each December, the objective coordinators will collect and collate research reports from each state for each objective, and develop a summary of progress within each objective. The summary and all reports will then be forwarded to the secretary who will post the reports on the web site and prepare hard copies for each committee participant in January. At the annual meeting, the objective coordinators will provide an oral summary of progress under each objective, and then allow a general discussion of the objective. Later in the meeting, the objective coordinators will lead small group discussions of plans for upcoming research. Any common protocols will be prepared or revised, and then posted on the web site.

Some research projects demand integration below the level of objective (e.g., subobjective 1A, p. 8). For such projects, a project leader will be identified to serve the duration of the project. The project leader will work with other project scientists to coordinate activities, similar to the role of objective coordinators within each objective. The annual meeting, the web site, and direct mailings will be used for planning and reporting research.

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Attachments

Land Grant Participating States/Institutions

IL, IN, KY, MD, MI, MN, MO, NE, NY, OH, OK, VA, VT, WI, WY

Non Land Grant Participating States/Institutions

National Program Leader, NIFA, Precision Planting