NE1025: Biology, Ecology and Management of Emerging Pests of Annual Bluegrass on Golf Courses
Statement of Issues and JustificationTurfgrass is a valuable and rapidly expanding component of our urban and rural landscape. Turfgrass covers 12 million ha in the U.S. (Potter & Braman 1991) and includes over 60 million lawns and more than 16,000 golf courses (Emmons 2000). Golf courses are an important component of the turfgrass industry. They are a source of green space in the urban environment and offer recreation and enjoyment for approximately 36 million Americans. Golf courses also generate jobs, commerce, economic development, and tax revenues for communities throughout the U.S. A recent report by the World Golf Foundation stated that golf contributes $62.2 billion worth of goods and services each year to the national economy (www.golf2020.com).
Few turfgrass species can tolerate the intensive management regimes (e.g., low mowing heights, low fertility, frequent cultivation, etc.) implemented on putting greens, tees, and fairways. Annual bluegrass (Poa annua) and bentgrass (Agrostis spp.) are well suited to these locations but are prone to many diseases and insect pests. Although most pest problems can be controlled with chemical pesticides, the general public is becoming increasingly concerned about the potential for pesticide exposure and long-term effects to humans and pets, as well as the possibility of ground and surface water contamination. The extensive use of chemical pesticides to control turfgrass pests also can reduce profitability of golf course operations. An integrated approach to disease and insect management (integrated pest management or IPM) can help alleviate some of the public concern about pesticide use and benefit the golf industry by increasing the efficiency of pest control efforts.
In January 2001, a broad-based group of stakeholders interested in golf course IPM in the Northeast met at Rutgers University (NJ). This focus group, part of a project funded by the NSF Center for IPM, included superintendents, university personnel, environmental and public health advocates, and representatives from the US Golf Association and the US EPA. The group discussed and prioritized key issues in IPM many of which are addressed in the current multistate turfgrass regional research proposal. Research and extension priorities cited by this group include (1) alternatives to current chemical pesticides, (2) forecast and sampling protocols for important pests of golf turf, and (3) a comprehensive Web-based treatment of golf turf IPM. For a complete summary of the focus groups' priorities refer to: http://northeastipm.org/ partners/priorities/turf2001.html. Our proposed research project will directly address these priorities as well as other gaps in knowledge and management practices associated with the annual bluegrass weevil (ABW) and anthracnose disease, two of the most important pest problems of annual bluegrass in the Northeast and Mid-Atlantic regions.
The importance of the work and the consequences if it is not done. Annual bluegrass is a common invasive species present on golf courses throughout the world. Biotypes of this species exhibit growth habits ranging from true winter annuals to long-lived perennials (Huff 2004). Annual bluegrass is often considered a weed by golf course superintendents, especially when it begins to encroach into newly seeded stands of creeping bentgrass (Agrostis stolonifera). Although some superintendents attempt to control annual bluegrass with herbicides, fumigants, or chemical growth regulators, these attempts often fail due to the competitive ability and prolific reproductive capacity of this grass species. In many cases, annual bluegrass becomes the dominant species in fairways and putting greens, and superintendents resort to managing it instead of the more pest-tolerant bentgrass species (Miltner et al. 2004). Annual bluegrass can provide an acceptable playing surface for putting greens and fairways when properly maintained, but this often requires extensive chemical inputs (Grant & Rossi 2005). Attributes of this species include its high tiller density, and tolerance of low cutting heights, shade and traffic. However, it is often maligned for its lack of stress tolerance, yellow-green color, prolific flowering habit, and its susceptibility to many diseases and insect pests (Beard 1973).
The maintenance of annual bluegrass on golf courses in the Northeast and Mid-Atlantic has become increasingly complicated by two emerging pests: the annual bluegrass weevil (Listronotus maculicollis) and anthracnose diseases caused by the fungus Colletotrichum cereale. The turfgrass anthracnose pathogen is commonly referred to as C. graminicola, a well-known pathogen of maize, but recent studies confirm that pooid-infecting isolates differ substantially from the maize pathogen, prompting the resurrection of the original name, C. cereale. Both pests can cause severe damage on annual bluegrass turf and can result in increased pesticide use and reduced golf-generated revenues. In severe cases, control of these pests depends almost entirely on synthetic pesticides. Reliance on multiple pesticide applications increases possibility of insects and pathogens developing resistance to these pesticides, as well as the cost of control. There is an urgent need to refine our understanding of the biology and ecology of these pests, to develop better IPM tools to assess and monitor their impact, and to discover and deploy alternative pest management practices whenever possible. By integrating these approaches, we seek to develop best management practices for the control of ABW and anthracnose on annual bluegrass, while promoting a model for environmental stewardship and cost effectiveness in other turfgrass habitats and highly managed ecosystems.
The annual bluegrass weevil is an insect of increasing concern in the northeastern U.S. where it is a notorious and damaging pest of close-cut annual bluegrass on golf courses and tennis courts. ABW injury to turfgrass was first reported in CT in 1931 (Britton 1932) and until the last 15 years has been concentrated in the metropolitan area of NY. Severe infestations are now being reported from all other states of the Northeast (DE, MA, ME, NH, NJ, NY, PA, RI, VT), west into Ontario and north into Quebec. It was problematic for the first time in MD last year, representing the southern front of its expanding range of impact in the Mid-Atlantic. Although not always present in turfgrass settings, the species has been reported from more than 40 states - therefore, the potential exists for significant spread of impact across a wide geographic range of the U.S. and Canada.
Every spring, superintendents contend with the movement of ABW adults from off-course overwintering sites to greens, tees, and fairways. As the insect completes two to three generations, the heavy damage inflicted by the stem-boring and crown-feeding larvae severely impacts the visual and functional quality of the turf. The problem is exacerbated because annual bluegrass is least vigorous and at a competitive disadvantage during the summer months, which coincides with the peak period of ABW feeding activity. Currently, there are no effective control options other than pyrethroid insecticides that target adults. In the best-case scenario, control is achieved with one well-timed perimeter spray, but it is not uncommon for superintendents to make 2-5 applications per season. Because ABW control depends almost exclusively on pyrethroids, this species may be under strong selective pressure for developing resistance to this chemical class.
Anthracnose is the name given to leaf diseases that occur throughout the world on almost all turfgrass species. They are particularly severe on annual bluegrass and to a lesser extent on creeping bentgrass. The anthracnose pathogen may cause a foliar blight or basal rot of leaf and sheath tissue (Smiley et al. 2005). Superintendents have been challenged in recent years by the increased incidence and severity of anthracnose diseases on golf courses throughout the U.S. (Dernoeden 2000, Landschoot & Hoyland 1995, Vermeulen 2003, Wong & Midland 2004) and Canada (Hsiang & Goodwin 1999). It is probable that the increased frequency of anthracnose on putting greens is associated with the intensive management practices (e.g., low cutting heights, increased mowing frequency, reduced nitrogen fertility, verticutting, and the use of plant growth regulators) currently employed by superintendents to meet the ever-increasing expectations of the golfing public.
Superintendents struggling to control anthracnose diseases often rely heavily on fungicides for disease suppression. However, relying solely on fungicides to control anthracnose is costly and has met with variable results, particularly when plants are under stress. Products are most effective when applied preventatively, but due to our incomplete knowledge of pathogen biology and fungicide timing, treatments are often applied too late to be effective. Because of the increasing use of fungicides to control anthracnose, resistance to the benzimidazole and strobilurin fungicides has recently occurred on many golf courses in the U.S. (Avila-Adame et al. 2003). It is likely that fungicide resistance will become more widespread if current chemical and cultural control practices are not altered.
If the proposed research on ABW and anthracnose is not conducted, the consequences will likely be (1) pest resistance development to pyrethroid insecticides and several of the anthracnose fungicide chemistries, (2) increased economic and environmental costs associated with the application of chemical pesticides used to control these pests, (3) decreased opportunities for the acceptance of new annual bluegrass varieties (should they be introduced into the marketplace), (4) reduced likelihood that anthracnose-resistant grass varieties will be developed and marketed, (5) loss of revenue in the golf course industry due to widespread turf failure, and (6) lack of an integrated chemical and biological management system for intensely managed turf.
Technical feasibility. All scientists involved with the ABW section of this project have experience with ABW and other turfgrass insects in studies that relate to morphology, reproductive biology, population ecology, phenology, degree-day modeling, dispersal, rearing, and various control alternatives (biological, cultural, chemical). The researchers involved with the anthracnose section of this proposal have been studying and publishing on anthracnose diseases and the population biology of C. cereale for several years. Many of the PIs have already shared isolates (NJ, PA, ON, CA) and data pertaining to the genetics (PA, NJ, ON) and pathogenicity of C. cereale (NJ, PA, ON). Management studies (cultural and chemical) have recently been initiated at several of the universities (PA, CA, NY, NJ, ON, CT) that are to participate in this project. Breeding programs in the region also have extensive collections of annual bluegrass (PA) and creeping bentgrass germplasm (NJ, RI) that will be shared and used in a coordinated fashion to determine the potential for genetic resistance to ABW and anthracnose. In addition, many of the PIs currently have Extension appointments and have extensive experience and successful track records in outreach and impact assessment.
Advantages of a multistate effort. Fungal and insect problems occur across state boundaries, so it is imperative that we develop control strategies that are appropriate for the broadest geographic region possible. In addition to enhancing protection of this extremely valuable commodity throughout the region, a multistate effort will increase the exchange of knowledge, experience, and techniques among many scientists who would not otherwise have a defined mechanism for cooperation. Individual efforts will be directed toward understanding the biology of these two pests. A major practical goal of the multistate project is to coordinate breeding goals and control regimes such that time and money are not wasted. Standardized surveys/ questionnaires conducted at the beginning and conclusion of this project will provide a comprehensive evaluation of pest importance, impact, and management practices across the region. Division of labor according to the primary expertise of the involved labs will improve the quality of the specific studies, and the outcomes from the various labs will help other labs advance more quickly with their studies. This regional approach will allow us to further examine multilocational studies across the Northeast and Mid-Atlantic for such areas as a degree-day model for ABW, pathogenicity of different fungal strains that cause anthracnose, efficacy of biological and biorational control agents for the two pests, and insect and disease resistance of annual bluegrass cultivars. Bringing entomologists, pathologists, management specialists, and plant breeders together will result in a better understanding of the biology and control of these two pests, and will allow for more efficient screening of annual bluegrass cultivars with optimal resistance to both ABW and anthracnose. Finally, a multistate effort will allow scientists to refine knowledge of these two pests and develop a set of "best management practices" (BMPs) that will help practitioners successfully control both pests while reducing pesticide use. Project participants will relay detailed, relevant findings to practitioners though regional and national seminars, symposia, electronic newsletters (NJ, NY), annual research field days (all states), and multi-authored publications in a coordinated fashion.
Anticipated impacts. Our interdependent research strategy will lead to the improved exchange of information among turfgrass entomologists, management specialists, breeders, and pathologists in the Northeast and Mid-Atlantic. A publication containing BMPs for annual bluegrass will be developed and disseminated to turfgrass managers in the region via this multistate effort. This and other applied publications developed from this project will be posted on our Website. This information will lead to improved management practices being adopted by golf course superintendents including the use of new biological, biorational, and chemical strategies, and new cultural and ecologically based control techniques. Adoption and implementation of this information by practitioners will result in improved management of ABW and anthracnose on annual bluegrass with reduced pesticide inputs, and ultimately economic and environmental health benefits across the region. Project impact will be measured with a survey conducted throughout the Northeast region in year 1 and 4 of this multistate project.
Back to Top