Pesticides for Turfgrass Pest Management: Uses and Environmental

Chapter 3

Pesticides for Turfgrass Pest Management: Uses and Environmental Issues Kenneth D. Racke

Downloaded by CORNELL UNIV on August 16, 2016 | http://pubs.acs.org Publication Date: December 29, 1999 | doi: 10.1021/bk-2000-0743.ch003

Global Health, Environmental Science and Regulatory, Building 308/2B, Dow AgroSciences, Indianapolis, I N 46268

Given the pest complex which may damage turfgrass, a variety of pesticides may be used to promote turf health. Insecticides such as acephate, chlorpyrifos, fipronil, halofenozide, imidacloprid, and spinosad may be applied to control soil inhabiting or surface feeding insects. Broadleaf and annual grass weeds may be controlled with such herbicides as 2,4-D, pendimethalin, triclopyr, and oxadiazon. Fungicides such as azoxystrobin, chlorothalonil, fenarimol, or triadimefon may be employed for fungal pests. Aspects of the chemical control paradigm for turf pest management will be examined. Pesticides for turfgrass pest management are selectively applied to achieve turf protection yet minimize potential environmental impacts. Environmental assessments of existing and new products for use on turf require generation of data related to persistence, mobility (leaching, surface runoff, volatility), bioavailability, and ecological impact. Research programs and approaches for environmental assessment of turfgrass pesticides will be reviewed. Finally, case study examples regarding research that may be associated with an existing turf pesticide product as well as research required for development of a new pesticide for the turf market will be examined.

Although much focus has been placed on the use of pesticides in agriculture, the urban environment also represents an important arena for the use of pest control chemicals (2). This chapter will examine aspects of the chemical control paradigm for turfgrass pest management, with particular emphasis on golf course uses.

© 2000 American Chemical Society

Clark and Kenna; Fate and Management of Turfgrass Chemicals ACS Symposium Series; American Chemical Society: Washington, DC, 1999.

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Turfgrass Pesticide Market Pesticide sales in the urban consumer and professional markets for 1991 were estimated at approximately 2.2 billion dollars (2). EPA estimates for 1993 place the volume of pesticides for agriculture, industrial/commercial/government (including golf courses), and home and garden use at 839,193, and 73 million pounds of active ingredient, respectively (3). In the urban environment, turfgrass pest control scenarios represent significant avenues of pesticide application and use. These include home lawns, golf courses, parks, athletic fields, commercial properties, and sod farms. A survey of home and garden pesticide use in the United States reported that 22% of home lawns were treated with pesticides by homeowners, and of those with private lawns, 12% utilized the services of a commercial lawn-care company (4). For golf courses, a recent survey reported only 20% utilized contract pesticide application services, with most opting for application by trained, in-house staff (5). Professional lawncare and golf course uses represent the major non-retail markets for turf pesticide products (Figure 1). Pesticides are heavily relied upon for pest management programs at the nation's 14,000+ golf courses, which represented upwards of 1.6 million acres in 1996 (Kline and Company, unpublished data). Approximately 300,000 acres of golf courses received at least one insecticide treatment during 1996. Insecticide products are most likely to be applied to fairways, tees, and greens, with proportionately less applied to roughs. Pre- and postemergence herbicide application represents the largest use on an acreage basis as compared with all pesticide products. Between 1.4 and 3.2 million herbicide acre-treatments per year were made between 1992 and 1996 (Kline and Company, unpublished data). The greatest quantities of herbicide use by volume during this period were applied to fairways and roughs. Compared to other turf markets, fungicides are more heavily relied upon in the golf course segment than for other segments. Approximately 160,000 and 189,000 acres of turf were treated with fungicides during 1994 and 1996, respectively, with greens being treated at a relatively higher percentage (73-93%) than other golf course areas (Kline and Company, unpublished data). It should be pointed at that as far as quantity of active ingredients applied, herbicides still predominate due to the large overall acreage and also use of older products with relatively higher application rates. For example, a survey of Hawaiian golf courses found a statewide average of 94,025 pounds of herbicide applied yearly, versus 19,051 pounds fungicide and 4,463 pounds of insecticide (6). Individual golf course data provided by the Golf Course Superintendents Association of America substantiate the importance of fungicides in golf course pest control programs, with comparable reliance upon herbicides and insecticides from an expense standpoint (Figure 2). An interesting observation from this survey is that spending on chemical fertilizers was roughly equivalent to that for all pesticide products combined for the average golf course (5). Pests and Products A plethora of pest insects, weeds, and diseases attack turfgrass areas of golf courses and lead to the need for management programs. Expectations of golfers are high with respect to the quality of turf on tees, fairways, and greens. At present, use of



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Figure 1. Turfgrass pesticide market for 1995/1996 with sales shown in millions of dollars (Kline and Company, unpublished data).

Figure 2. Average annual expenditures (dollars) on turfgrass chemicals for individual golf courses during 1997 (5).


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pesticides represents a major means of control of turfgrass pests of golf courses, and the chemical control paradigm has been widely adopted. Insects and Insecticides. Insect pests of turf include surface feeders which actively damage foliage through chewing or sucking, and also subsurface feeding insects which may devour roots and leave plants vulnerable to drought and desiccation. In addition, the burrowing habit of the mole cricket results in unsightly disruption of the turf/ thatch/soil surface. There are significant regional differences between the types of insect pests encountered on golf courses. For example, mole crickets and fire ants are typical pests of Southeast U.S. turf whereas Hyperodes weevils are common pests of the Northeast U.S. Examples of surface and subsurface feeding insect pests are listed in Table I. For surface feeding insects, well-established products such as chlorpyrifos, carbaryl, and acephate are the major compounds of use (Kline and Company, unpublished data; 5). Newly introduced insecticides for surface feeder control include bifenthrin and spinosad. For subsurface grub control, although established products such as chlorpyrifos and trichlorfon continue to be widely used, there have been recent and highly successful introductions of the new products imidacloprid and halofenozide (7). For mole crickets, established products such as acephate and isazophos have been joined by the recent introduction of fipronil. Weeds and Herbicides. Weeds infesting turf include both grasses and broadleaves. Examples of common grass and broadleaf weed pests of turf are listed in Table I. In addition to terrestrial weeds, pond areas of golf courses are also subject to problems with nuisance aquatic weeds and algae. Grass weed control largely involves preemergent applications of such products as pendimethalin, trifluralin, benefin, dithiopyr, prodiamine, and oxadiazon. Broadleaf weed control predominantly relies upon postemergent applications of such products as 2,4-D, MCPA, and dicamba. Combination products containing one or more of these active ingredients are commonly employed to achieve an acceptable spectrum of activity across weed pest varieties. Several of the active ingredients employed for weed control on golf courses have been employed for many years. An example would be 2,4-D, which has seen over 50 years of use. Diseases and Fungicides. A large variety of plant pathogens may infect and damage turfgrass. Examples of common turf diseases are listed in Table I. Products for turf disease control include those which have contact or systemic activity such as chlorothalonil and flutolanil, respectively. In addition, products demonstrating broad-spectrum disease control both systemically and by contact have been highly successful, as exemplified by the recent introduction of azoxystrobin. Turf Pest Management Trends Although the chemical control paradigm is still largely employed in turf pest management systems, there have been significant changes during the past several years. These changes include the increasing importance of integrated pest


49 Table I. Common Turfgrass Pests and Pesticides.

Insect/Nematode Control Insects


Insecticides

Surface Feeders Chinch bugs Sod webworms Cutworms Armyworms Chlorpyrifos (Dursban*) Carbaryl (Sevin) Acephate (Orthene) Bifenthrin (Talstar) Spinosad (Conserve*)

Subsurface Feeders Grubs Mole crickets Nematodes Imidacloprid (Merit) Chlorpyrifos (Dursban) Trichlorfon (Dylox) Halofenozide (Mach II) Fipronil (Chipco Choice) Acephate (Orthene) Isazophos (Triumph)

Weed Control Weeds

Herbicides

Grasses Crabgrass Goosegrass Annual bluegrass Dithiopyr (Dimension) Prodiamine (Barricade) Oxadiazon (Ronstar) Pendimethalin Simazine Benefin + Trifluralin (Team*)

Broadleaf White clover Dandelion Plantain 2,4-D MCPA,MCPP Dicamba Dichlorprop 2,4-D + MCPP + Dicamba (Trimec) Triclopyr + Clopyralid (Confront*)

Disease Control Diseases

Fungicides

Brown patch Pink snow mold Dollar spot Contact or Systemic Mancozeb (C) Chlorothalonil (C) Flutolanil (Prostar) (S) Metalaxyl (Subdue)(S) Fosetyl al (Aliette) (S)

Pythium blight Gray snow mold Anthracnose Contact/Systemic Azoxystrobin (Heritage) Iprodione Propiconazole (Banner) Triadimefon (Bayleton) Fenarimol (Rubigan*)

*Trademark of Dow AgroSciences


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management and the continued introduction of both conventional and biological pesticides into the turfgrass manager's chemical toolbox. In the future, the role of biotechnology may also play a larger role with respect to the incorporation of favorable traits (e.g., insect resistance) into turf varieties. Integrated Pest Management. The concept of Integrated Pest Management (IPM) arose originally within the agricultural pest control arena. The philosophy of IPM places less emphasis on chemical control measures and more emphasis on the use of all available control measures (e.g., chemical, cultural, biological) in an integrated fashion for effective management of insect, weed, and disease pests. Use of chemicals has a clear place in the IPM approach, but rather than rely on prophylactic or calendarbased spray application schedules, the use of chemicals at specific times and sites identified by scouting, monitoring, or modeling, and justified economically, is encouraged. There has been a significant degree of recent research on IPM for turfgrass pest management, and comprehensive summaries are available (8,9). Despite the volume of research methodologies and academic approaches, IPM has been only slowly adopted in the turfgrass pest management arena. With respect to the largest turf market segments (home lawncare, professional lawncare, and golf course), the golf course environment has offered the greatest potential for adoption of IPM approaches because golf course superintendents already monitor their landscapes and use cultural tactics to minimize disease and insect problems. A survey of golf course superintendents revealed that an average of 86% reported at least some involvement with an IPM program, which resulted in a reported average reduction in pesticide use of 21% (5). Few comprehensive IPM programs have been developed for turfgrass, however, and Potter (70) summarized major impediments to broader adoption of IPM in the golf course environment. These included high expectations of golfers for nearperfect turf quality, cost-ineffectiveness of available pest monitoring and sampling methods, lack of reliable and cost effective alternatives to pesticides, and a relatively weak research and extension base. It is anticipated that continued efforts will be devoted to meeting these challenges given the cost of chemical control measures and issues associated with their use. Continued Introduction of Conventional Products. Use of some turf pesticide products has endured for many years. Such herbicide products as 2,4-D and atrazine, and insecticide products as chlorpyrifos and carbaryl have been employed for 25-plus years for turf pest control. There have continued to be new product introductions for all classes of pesticide products for turf use through the years. The past several seasons have seen the introduction of several innovative and noteworthy products, especially those targeted at insect control. These include imidacloprid (1995) and halofenozide (1997) for grub control, fipronil (1996) for mole cricket control, and spinosad (1997) for surface feeder control. The recent introduction to the turfgrass market of azoxystrobin (1997), a broad-spectrum fungicide, has greatly impacted professional turf disease management. Although several of these products have been approved by E P A as "reduced risk" alternatives to existing chemical products, it is noteworthy that characteristics of some new products may actually discourage IPM approaches. For example, due to residuality of control and desirability of targeting


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early life stages of grub pests, both imidacloprid and halofenozide may be applied weeks or months prior to pest egg hatch. This practice might tend to discourage soil sampling and use of selective, curative control measures (7,11). Availability of Biologicals. Biological products, especially those targeted at insect control, are also available to the turfgrass pest manager. These include the recently approved Beauvaria bassiana (Naturalis-T), a fungi which affects grasshoppers, mole crickets, and sod webworms. Other options available include various Bacillus thuringiensis (Bt) products (XenTari, Condor, Dipel) which produce bacterial toxins active against sod webworms, and Heterorhabditis bacteriophora (Cruiser) a nematode that attacks white grub larvae. Nearly all of the biological products, with the exception of B. bassiana, are narrow in terms of spectrum of activity, often targeting just one specific pest or at most a specific taxonomic group. The extent to which these biologicals are being employed within the golf course environment is somewhat unclear, but limited adoption may be due to perceived lower consistency, reliability, and versatility and higher cost than conventional pesticides (9,10). A recent survey of golf course superintendents did not identify any of the biological products as primary treatments, although a marketing assessment revealed that during its first year of introduction B. bassiana accounted for approximately 1% of total insecticide active ingredient use by golf courses (Kline and Company, unpublished data; 5). Increased Regulatory Scrutiny. The turfgrass care industry in general is accustomed to a significant degree of regulation, as exemplified by a recent series of articles in Grounds Maintenance magazine titled "Are regulations killing our industry?" (12,13). Pesticides represent one of the most highly regulated product groups, and an incredible set of requirements must be met in order to introduce and market a product for use in the agricultural or urban environment. The costs of required pesticide registration studies have been steadilyrising,and one important factor behind the increasing costs is increasing regulatory scrutiny. For example, the Food Quality Protection Act of 1996 amended basic U.S. pesticide regulation to require assessment of potential human exposure to a given pesticide from all potential sources (dietary, occupational, drinking water, residential reentry,...), simultaneous consideration of pesticides with common mechanisms of toxicity, and additional testing of potential endocrine effects of pesticides. One outcome of the high cost of product development is that it is difficult for basic manufacturers to economically justify pursuit of new products exclusively for the turfgrass market. Instead, new active ingredients are often simultaneously developed for introduction both for urban and agricultural uses. Increased regulatory scrutiny also favors the development of new pesticide products with improved safety profiles. For example, the U.S. EPA has established a "reduced risk" pesticide program whereby new active ingredients with lower toxicity or less potential for environmental impact are given preferential treatment and accelerated registration review and approval. Such was the case with the recently introduced fungicide azoxystrobin and insecticide spinosad, both of which were approved as reducedriskproducts by the EPA during early 1997 (U.S. EPA Press Release, February 28,1997).


52 Environmental Considerations


There are a number of environmental considerations that arise from the use of pesticides in the turfgrass environment. These include potential impacts on surface and groundwater quality, persistence in soil, effects on nontarget terrestrial and aquatic organisms, and human exposure. These topics have been summarized in recent volumes by Racke and Leslie (1) and Balogh and Walker (14). A brief discussion of environmental considerations related to turf pesticide use and some relevant examples are described in the following section. Surface Water Quality. Pesticides present in surface water may be of concern from the standpoint of potential impacts on nontarget aquatic organisms (fish, invertebrates, plants) as well as with respect to potential drinking water exposure of humans. Pesticides and fertilizers applied to turfgrass areas may reach water via spray drift or surface runoff. Research on potential surface runoff of pesticides has resulted in the general finding that limited transport occurs from treated turfgrass areas under most conditions (15-18). For example, Harrison et al. (15) reported no detectable concentrations of the highly sorbed pesticides chlorpyrifos and pendimethalin and small quantities (0.8-1.6% of applied) of several soluble herbicides (2,4-D, dicamba) in runoff water from treated turf plots subject to a > 100-year return frequency simulated rainstorm. The magnitude of pesticide transport observed in turfgrass environments is much lower as compared with transport observed from bare soil or row crop situations under similar treatment for several reasons. These include the lack of significant sediment erosion that might carry sorbed pesticides from turf areas, increased sorption by the thatch as compared with soil, and increased infiltration of water and decreased runoff water volumes in turfgrass. The increased retention of pesticides in turfgrass areas is exemplified by the employment of untreated grassed buffer/filter strips as a mitigation measure for reducing edge-of-field losses of pesticides from both agricultural fields and turfgrass areas (18-20). Surface water monitoring of golf course and other urban watersheds reveals detectable but trace quantities of turfgrass pesticides. Cohen et al. (21; Cohen personal communication) summarized the results of a number of North American golf course surface water monitoring studies, and overall results indicated that widespread and/or repeated water quality impacts by golf courses was not occurring at the study sites. None of the authors of the individual studies concluded that toxicologically significant impacts were observed, although scattered exceedences of some water quality criteria were observed. Similar results have been reported from golf course surface water monitoring studies conducted in Japan (22-24). Under certain conditions, such as when high rainfall occurs shortly after application to steep slopes, surface transport with water can move greater quantities of less highly sorbed pesticides. For example, Smith and Bridges (25) reported that between 10 and 14% of several soluble herbicides (dicamba, mecoprop, 2,4-D) were ^ transported with runoff water from simulated fairways subjected to 4 intense rainfall events within 192 hours after treatment. In rare instances, such large runoff events coming immediately after application may lead to some impacts on aquatic organisms, as exemplified by a reported fish kill in a New Jersey lake which followed a fenamiphos application to a nearby golf course (26). Clearly, specific local conditions


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conducive to surface runoff impacts may justify both prudent application procedures and water management practices (18). Groundwater Quality. Pesticides and nutrients (e.g., nitrate) present in groundwater are primarily of concern from a human drinking water exposure standpoint. Pesticides and fertilizers applied to turfgrass areas may leach to subsurface water via chromatographic movement through the network of soil micropores and/or via macropore flow. Research on potential leaching mobility of pesticides has resulted in the general finding that limited transport occurs from treated turfgrass areas under most conditions (15-18, 27-29). For example, Smith and Bridges (25) reported only trace quantities (0.1-0.9% of applied) of several water-soluble herbicides (2,4-D, dicamba, mecoprop) leached from simulated bentgrass and bermudagrass greens during a 70 day period. The organic thatch layer, which has a significant ability to sorb and retain pesticide residues, has been credited with much of the "filter" effect which turfgrass confers with respect to soil leaching potential (27, 30-32). Groundwater monitoring of golf course areas reveals detectable but trace quantities of turfgrass pesticides and fertilizer components may reach groundwater under some conditions, but the frequency of detection and magnitude of residues are generally lower than observed during similar surface water monitoring surveys. For example, Cohen et al. (21; Cohen personal communication) summarized the results of a number of North American golf course groundwater monitoring studies, and overall results indicated that widespread and/or repeated water quality impacts by golf courses was not occurring at the study sites. The frequency of exceedence of Health Advisory Limits (HALs) by individual pesticides in the groundwater samples analyzed in the studies was approximately 0.07%. Specific instances in which pesticide residues are detected in groundwater beneath turfgrass areas at concentrations of concern are limited, but may be associated with unusual conditions or management practices. For example, a survey of groundwater under Cape Cod golf courses resulted in detection of chlordane and heptachlor residues above HAL limits, and the presence of these discontinued pesticides may have been attributable to repeated, heavy applications coupled with preferential flow of bound particulate phase (33). Similarly, an EPA study reported that the presence of trace residues of DCPA (chlorthal-dimethyl) in water samples taken from individual wells was directly correlated with its heavy use on golf courses and commercially maintained landscaping in urban areas (34). Nontarget Wildlife Impacts. Considerations regarding turf pesticides and nontarget wildlife include potential impacts on birds, wild mammals and amphibians, and soil invertebrates. Golf courses appear to represent significant wildlife habitat in the urban environment, as documented by the numbers and variety of bird species that have been observed during surveys (14, 35). It is also worth noting that wildlife habitat areas on and surrounding golf courses may not be routinely treated with pesticides; the most heavily treated areas tend to be those of limited value for wildlife (e.g., tees, greens), Research on earthworm and soil arthropod populations in turfgrass has demonstrated that pesticides differ greatly in their potential for causing adverse effects. For example, use of most herbicides and some insecticides (e.g., 2,4-D, dicamba, isofenphos) had little or no impact on earthworm populations, whereas some insecticides and fungicides (e.g., carbaryl, bendiocarb, benomyl) caused severe or very



54 severe toxicity (51-99% population reduction) under some conditions examined (5638). With respect to turf pesticides and avian species, detailed accounts of bird impacts are not abundant in the open literature, and available data generally indicates that bird populations in golf course areas are not adversely affected by the use of pesticides. In the specific case of granular diazinon, incident reports of bird mortalities following use of this product on turfgrass led the U.S. E P A in 1990 to prohibit use of the product on golf courses and sod farms (59). The move to ban versus tighten labeling restrictions was a controversial one in that several field monitoring studies were completed which demonstrated a lack of bird impacts with a proposed label limit of 2 applications of 2 lb a.i./acre per year (59). E P A later completed a comparative analysis of acute avian risk resulting from use of granular insecticides and nematicides on turfgrass (40). Although the screening level approach employed in the risk analysis in reality represented a hazard ranking (i.e., avian LD50/square foot of applied granules), a number of manufacturers responded to the analysis with voluntary labeling modifications that reduced potential avian exposure (e.g., application rate reductions, post-application irrigation requirements) (41). Despite theoretical concerns that may be raised based on such calculations, evidence from large-scale monitoring studies of bird populations on treated and untreated golf courses has demonstrated a lack of significant impacts for currently used products under most conditions (55, 42, 43). Persistence and Degradation. Pesticides present in the turfgrass ecosystem are degraded through a variety of mechanisms, both abiotic (e.g., photolysis, hydrolysis, volatilization) and biological (e.g., plant metabolism, microbial degradation). A full discussion of the variety of factors that may affect pesticide persistence in turf can be found in available review articles (1,14). It should be recognized that observed pesticide dissipation within an environmental compartment (e.g., soil, plan) can be the result of both degradation and transport processes (e.g., volatilization). Some of the earliest synthetic turf pest products were chlorinated hydrocarbon insecticides (e.g., chlordane, dieldrin, aldrin, heptachlor) which were eventually removed from the marketplace due to undesirably long persistence and potential bioaccumulation within ecosystems. These products were replaced by much less residual products, often with degradation half-lives of a few weeks or months. For at least some insecticide products, biodegradability can lead to the problem of enhanced rates of microbial degradation. Enhanced degradation is the accelerated rate of pesticide degradation, by adapted soil microorganisms, observed in soil following previous application of the pesticide (44). Isofenphos is one chemical that is susceptible to this phenomenon, and although a first soil application of the product results in effective residuality, subsequent applications are rapidly degraded by adapted microorganisms. The decreased persistence and associated soil insect pest control failures led to the withdrawal of this product from the corn rootworm market during the early-1980's (45), and enhanced degradation was subsequently observed in turfgrass thatch and soil with a prior history of isofenphos use (46). Not all pesticides are able to induce enhanced rates of microbial degradation, and the phenomenon is fairly specific with respect to chemical structure. The inherent biodegradability of a pesticide, its degree of bioavailability in soil and thatch, and nutritive value of one or


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more metabolites to support microbial metabolism and growth influence whether microbes can proliferate and cause rapid rates of pesticide degradation for subsequent applications. At least several additional turfgrass pesticides, including 2,4-D, carbaryl, and fenamiphos have been shown to undergo enhanced rates of degradation in soil or turfgrass thatch under some conditions (47, 48), whereas other products are apparently resistant to the phenomenon (49). Human Exposure Considerations. Although a detailed discussion is beyond the scope of this chapter, there are also human exposure considerations related to the use of pesticides on turfgrass. In addition to potential applicator exposure, there is the potential for exposure to those reentering treated turfgrass areas. The primary route of potential reentry exposure involves dermal uptake from dislodgeable residues on turfgrass foliage, although inhalation exposure from the presence of volatilized pesticide residues in air can also occur. Studies of the fate of total and dislodgeable (i.e., removed via contact and abrasion) residues of pesticides on turfgrass foliage have demonstrated that a very low percentage (5-10% at most) of the total residue present immediately after application is in dislodgeable form and concentrations decrease rapidly with time (50, 51). Some researchers have completed biomonitoring studies of the uptake and excretion of pesticide residues in individuals reentering treated turf areas, and results demonstrate adequate safety margins (52, 53). Additional research on both application and reentry exposure in turfgrass is being completed by the Occupational and Residential Exposure Task Force, an industry association currently working cooperatively to meet an EPA data call-in (54). Regarding potential inhalation exposure, monitoring of air during and following application to turfgrass confirms the very low levels that may be present, indicating that this is at most a secondary route of potential exposure (55). Turf Pesticide Research and Testing The safe and effective use of pesticides for turfgrass pest management requires the availability of a significant body of research information related to the behavior and potential effects of these chemicals. This information is employed by users, regulators, manufacturers, researchers, and consultants in making informed pest management recommendations andriskmanagement decisions. Research on turfgrass pesticides begins at the basic manufacturer level in association with new product development and testing to meet regulatory requirements. Industry research related to product stewardship as well as independent research to address new areas of science and emerging issues follow the introduction of a pesticide product into the turf pest management market. All of these research avenues are important for increasing the knowledge base on turf pesticides and for providing information related to effective pest management as well as environmental and human health issues that may arise from turf pesticide use. The following paragraphs will briefly describe the nature of these complementary research areas in relation to turfgrass pesticides, and case study examples of an older, established product and a very recently introduced product will be examined.



56 Development and Registration. Research and development related to discovery of new pest control products is an integral part of a number of major agrochemical manufacturers and suppliers including Novartis, Monsanto, Zeneca, Bayer, DuPont, Dow AgroSciences, and AgrEvo. Screening biology and chemistry programs to identify promising new chemistries for further testing are important components of this effort and, as noted earlier, pursuit of turfgrass pest products is usually incorporated into broader discovery targets related to major pest groups (e.g., broadleaf weeds, Lepidoptera). Significant efforts are undertaken to characterize biological efficacy under real-world field conditions, and importance is placed on understanding factors potentially affecting or enhancing performance. Generation of human safety and environmental impact data for regulatory review and approval is another major undertaking of the new product development process (see Table Π). Over 120 studies for an individual pesticide candidate may be completed during a development period of some 7 to 9 years to generate the necessary data submission package for agencies such as the Office of Pesticide Programs at U.S. EPA or the Department of Pesticide Regulation at California EPA. Although the majority of regulatory testing is generic in nature and related to the molecule rather than specific environments or use patterns, there are studies directly related to use on turfgrass that are either routinely required or triggered by results of preliminary assessments. Examples of these would include generation of turf foliar dislodgeable residue data (for assessment of potential human exposure) and monitoring of avian impacts under field use conditions.

Table II. Major Categories and Selected Examples of New Product Registration Testing Requirements. Product Chemistry Description of manufacturing process Technical impurity identification Analytical methods

Physical/Chemical Characteristics Solubility Vapor pressure Octanol water partition coefficient

Mammalian Toxicology Acute oral toxicity 90-day feeding study Chronic feeding study Teratogenicity study 2-Generation reproduction study

Ecotoxicology Acute avian toxicity Avian dietary toxicity Acute fish toxicity Fish life cycle study Acute freshwater invertebrate toxicity

Residue Chemistry Nature of residues in plants & animals Analytical methods for residue analysis Magnitude of residues in field crops

Environmental Fate Hydrolysis Photodegradation in water Aerobic soil metabolism Leaching and adsorption/desorption Soil field dissipation Accumulation in fish Groundwater monitoring

Worker and Reentry Exposure Foliar residue dissipation Dermal and inhalation dosimetry



57 In addition to external review and approval, R&D companies involved in new product development utilize a series of decision-making or advancement gates at various points in the process so that assessments based on results of safety testing, efficacy trials, and marketing evaluations can occur. These assessments can result in advancement or in delay or in project cancellation based on the accumulated information, and current indications are that no more than 1 or 2 products reach commercial status of more than 50,000-100,000 that may have been through the screening process. The new product development process is a costly one, and it may take from 10-15 years or more for the costs incurred during the development process (between 50 and 100 million dollars) to be recouped through commercial product sales (56). A final note is that through the reregistration and data call-in processes, basic manufacturers are obliged to maintain their databases of safety information on existing products so as to meet current study guidelines and new standards of performance. Product Stewardship. Once a turfgrass product has been introduced into the marketplace, there is a need for ongoing generation of new research information related to product performance and safety. This product stewardship-based research is not driven by regulatory requirements, but rather by the desire to uphold the highest standards of ethics and environmental responsibility by addressing new areas of science and emerging issues. Such research may be related to product quality, performance, and efficacy. It is difficult within new product development programs to evaluate every possible use scenario, and additional testing may be required. For example, the suitability of a tank mix partner and potential for turfgrass phytotoxicity may need to be evaluated when another new product enters the marketplace. Alternately, product stewardship research may address a specific question or technical issue related to environmental behavior, ecological impact, or human safety. For example, although EPA registration requirements for the field soil dissipation guideline may be met by completion of a bare-soil study at maximum application rate, a manufacturer with a turfgrass product may wish to examine the fate of a more typical application rate of the product in turf foliage, thatch, and underlying soil to provide data for more realistic assessments. Product stewardship research represents continuing investment in product support by the basic manufacturer to ensure that products are long-lived and continue to be used efficaciously and safely with appropriate management practices. Product stewardship research may be conducted in a proprietary nature by scientists on staff with the product manufacturer or funds may be provided to an outside contractor or university for investigation support. Independent Research. Independent research is another important avenue by which the knowledge base on turfgrass pesticides is expanded. Such turf pesticide research might be completed at a university, a federal or state research laboratory, or by a private research organization. Funding for such research may come from multiple sources including government agencies, foundations, user groups, or industry. Independently funded research often carries great credibility with the general public, user groups, and advocacy groups, and serves as an important complement to work that might be completed from a more proprietary standpoint. The recent environmental turfgrass research program sponsored by the U.S. Golf Association is an excellent example of this type of research. Results of this program, summarized in


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other chapters within this volume, have added considerably to the general knowledge base on turfgrass pesticide behavior, particularly with respect to the fate of pesticides in the golf course environment. Case Study: Chlorpyrifos (Dursban). Chlorpyrifos provides an example of turfgrass research efforts that may be associated with a well-established product. The original environmental safety and health data for this product, first discovered by the Agricultural Products Department of The Dow Chemical Company (now Dow AgroSciences) in the early 1960's, supported the registration of chlorpyrifos for turfgrass use as Dursban 2E in 1965. Since that time, from a registration research standpoint, additional data call-ins have occurred periodically to upgrade and modernize the database. For example, in 1991 the U.S. E P A requested generation of new data for chlorpyrifos fate on turfgrass under field conditions. As a result, studies to meet current guideline requirements were completed on Kentucky bluegrass in Indiana and St. Augustinegrass in Florida (57). Another example of regulatory research was occasioned by a data call-in issued by U.S. E P A in 1993 for foliar residue dissipation, applicator exposure, and reentry exposure (dermal and inhalation) for all turfgrass pesticide products. In support of chlorpyrifos, Dow AgroSciences and a number of other basic manufacturers of turf pesticide products formed an Occupation and Residential Task Force to jointly develop generic data (e.g., transfer factors, spray deposition on clothing) to meet the general aspects of the data call-in requirement (54). Each company is also generating foliar dislodgeable residue data on representative formulations for each active ingredient to provide chemical-specific data. Given the economic importance of urban uses of chlorpyrifos, Dow AgroSciences has supported a number of product stewardship-based research initiatives on the product. One example is related to a company research project which addressed the potential for migration of chlorpyrifos from treated turfgrass areas to sensitive surface water habitats with runoff water. To this end, steeply-sloped bluegrass and Bermudagrass plots on a golf course in Kentucky were marked off after application, subject to simulated rainfall, and runoff water analyzed for residues of transported chlorpyrifos (58). Another example is provided by company research efforts related to development of appropriate methodology for accurate estimation of potential reentry exposure to chlorpyrifos or other turfgrass pesticides. To this end, indirect methods for estimation of exposure (Dow "drag-sled" method to determine dislodgeable foliar residues and potential dermal exposure and air monitoring to determine potential inhalation exposure) were compared to a biomonitoring method (urine of test subjects reentering treated turfgrass area monitored for appearance and level of TCP, the major metabolite of chlorpyrifos). Results confirmed the usefulness of the more flexible and less costly indirect method developed by Dow AgroSciences (53). A final example may be provided by reference to research on potential avian effects of turfgrass pesticide use sponsored by Dovt AgroSciences with a Canadian research group. This group examined the potential impact resulting from the use of several turfgrass pesticides on population levels and nesting success of the American robin in suburban turfgrass environments (59). The widespread and historic use of chlorpyrifos in turfgrass markets (golf course, professional lawncare, home lawncare) has also made it a common subject of independent research efforts. Many of these efforts have involved highly focused and


59


unique approaches to determination of the potential environmental fate, ecological impact, and human safety assessment for chlorpyrifos in the turfgrass system. Independent research on chlorpyrifos has examined such diverse topics as dissipation under golf course fairway conditions (60), leaching mobility on golf course greens (61), sorption characteristics of turfgrass thatch (31), fate of residues during composting of grass clippings (62), and dissipation of foliar dislodgeable residues (50, 51). Case Study: Spinosad (Conserve). Spinosad provides an example of research efforts that may be associated with development of a new turfgrass pesticide product. Screening of fermentation broths by Dow AgroSciences during the mid-1980's demonstrated activity against several key target insect pest groups in a broth derived from a soil sample. This activity was attributed to metabolites produced by a specific soil bacterium during fermentation, and these were characterized as "spinosyns". The structures of spinosyn A and spinosyn D, the active ingredients in spinosad, were eventually determined (63). Key milestones in the characterization and development of spinosad as a new insecticide product are summarized in Table III. Regulatory testing in support of spinosad development was conducted during the early 1990's. Studies ranged from determining analytical methods for detection of spinosad in environmental samples to evaluating the rate and pathway of degradation in soil, water, plants, and animals (64, 65). In addition to the standard package of studies required for registration, special testing and research was also completed. For example, the fate of spinosad following application to turfgrass and ornamentals was assessed (Dow AgroSciences unpublished report). Research on the mode of action of spinosad, which turned out to involve effects at a novel target site in the nicotinic acetylcholine receptor of the insect nervous system, was also completed and published (66). To determine the fate of spinosad in water following an accidental overspray, a sediment/water pond microcosm study was conducted (65). Results of the testing program for spinosad yielded not only a complete regulatory database, but revealed a very positive safety and environmental profile. In fact, spinosad's properties were so favorable that EPA granted the product "reduced risk" status (as compared with existing insecticide products) and approved it under an expedited regulatory review (U.S. EPA Press Release, February 28,1997). The basis for EPA's decision was that spinosad possessed low mammalian toxicity, low nontarget organism toxicity, and excellent compatibility with IPM programs. In addition to regulatory testing, a significant field research program to characterize performance under field conditions was undertaken. To assist with characterization of the efficacy of spinosad against turf and ornamental insect pests, an Experimental Use Permit (EUP) program for 1996 and 1997 was conducted. This EUP included real-world testing at a number of g^lf courses. Dow AgroSciences worked with these golf courses to collect data on effectiveness of label use rates and use directions, including facilities in Florida, California, North Carolina, Indiana, and New Jersey. Results of the EUP program indicated excellent efficacy against key Lepidoptera target pests including sod webworms, black cutworms, and fall armyworms. Testing also indicated that the Conserve formulation of spinosad proved to be non-phytotoxic to turfgrasses, which was an important finding. In addition,


60


Table III. Major Milestones in the Development of Spinosad 1982

Soil sample collected from rum distillery in the Virgin Islands

1985

Screening of fermentation broth from soil sample demonstrates biological activity towards mosquito and southern armyworm larvae

1985

Newly discovered bacterium isolated from fermentation broth, Saccharopolyspora spinosa, found to produce active substances known as "spinosyns"

1989

Structure of spinosyn A determined

spinosyn A: spinosyn D:

R = H MW = 732 R = CHa MW = 746

1989

Field efficacy trials initiated

1991

Predevelopment regulatory research program initiated

1994

Submission of registration data package to U.S. E P A

1994

Product commercialization and development program initiated

1996

Initiation of Experimental Use Permit program for turfgrass pest control

1996, 1997

Patents issued for production of spinosyns

1997

Registrations approved for cotton (Tracer*) and turfgrass (Conserve)

1997

Commercial launch of Tracer and Conserve

*Trademark of Dow AgroSciences

helpful insight was gained into how best to make spinosad packaging, delivery and labeling as user-friendly as possible. In addition to the research programs related to safety and efficacy testing, additional efforts with respect to development of suitable formulations and packaging, construction of a manufacturing facility, design of a distribution network, and development of marketing and sales programs also required considerable effort. The end result of the 12 year research program, which involved an R & D investment in


61 excess of $60 million, was introduction of a new pesticide product for the turfgrass and agricultural insect pest management markets.


Summary and Conclusions Golf course turf pest control is strongly reliant on the use of pesticides, especially fungicides. Pesticide products continue to be developed for the turf pest market; several successful launches of outstanding new products have recently occurred. Environmental considerations related to turf pesticide use include surface and groundwater quality, wildlife impacts, and degradation processes. Development of a new turf pesticide involves a major commitment to generation of data related to both efficacy and health and environmental safety. Both product stewardship-based and independent research continue to expand the knowledge-base with regard to potential impacts and management practices for use of pesticides in the turfgrass environment. Literature Cited 1. Pesticides in Urban Environments: Fate and Significance; Racke, K. D.; Leslie, A. R., Eds.; ACS Symposium Series No. 522; American Chemical Society, Washington, DC, 1993. 2. Hodge, J. E. In: Pesticides in Urban Environments: Fate and Significance; Racke, K. D.; Leslie, A. R., Eds.; ACS Symposium Series No. 522; American Chemical Society, Washington, DC, 1993; pp 10-17. 3. Aspelin, A. L. Pesticide Industry Sales and Usage: 1992 and 1993 Market Estimates; U.S. Environmental Protection Agency, 733-K-94-001, June 1994, Washington, DC. 4. Whitmore, R. W.; Kelly, J. E.; Reading, P. L.; Brandt, E.; Harris, T. In: Pesticides in Urban Environments: Fate and Significance; Racke, K. D.; Leslie, A. R., Eds.; ACS Symposium Series No. 522; American Chemical Society, Washington, DC, 1993; pp 18-36. 5. 1998 Plant Protection and Fertilizer Usage Report; Golf Course Superintendents Association of America, Lawrence, KS, 1998. 6. Brennan, B. M.; Higashi, A. K.; Murdoch, C. L. Estimated Pesticide Use on Golf Courses in Hawaii; Research Extension Series 137, College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu, HI, 1992. 7. Potter, D. A. Prosource; 1998, May-June, 14-17. 8. Handbook of Integrated Pest Management for Turf and Ornamentals; Leslie, A. R., Ed.; Lewis Publishers, Boca Raton, FL, 1994. 9. IPM Handbook for Golf Courses; Schumann, G. L.; Vittum, P. J.; Elliott, M. L.; Cobb, P. P., Eds.; Ann Arbor Press, Chelsea, MI, 1997. 10. Potter, D. A. In: International Turfgrass Society Research Journal 7. Carrow, R. N.; Christians, Ν. E.; Shearman, R. C., Eds.; Intertec Publishing Corporation, Overland Park, KS, 1993. 11. Vittum, P. J. Grounds Maintenance; 1997, September, 6-8. 12. Hogan, G. K. Grounds Maintenance; 1998, March, 15-18, 103. 13. Liskey, E. Grounds Maintenance; 1998, March, 20, 24, 28, 32, 115.



62 14. Balogh, J. C.; Gibeault, V . Α.; Walker, W. J.; Kenna, M. P.; Snow, J. T. In: Golf Course Management and Construction: Environmental Issues; Balogh, J. C.; Walker, W. J., Eds.; Lewis Publishers, Boca Raton, Florida, 1992; pp 1-37. 15. Harrison, S. Α.; Watschke, T. L.; Mumma, R. O.; Jarrett, A . R.; Hamilton, G. W. In: Pesticides in Urban Environments: Fate and Significance; Racke, K . D.; Leslie, A . R., Eds.; ACS Symposium Series No. 522; American Chemical Society, Washington, DC, 1993; pp 191-207. 16. Shuman, L . M.; Smith, A . E.; Bridges, D. C. In: Clark, J. M.; Kenna, M . P., Eds.; Fate of Turfgrass Chemicals and Pest Management Approaches; ACS Symposium Series, American Chemical Society, Washington, D C , 1999. 17. Watschke, T. L.; Mumma, R. O.; Linde, D.; Borger, J.; Harrison, S. In: Clark, J. M . ; Kenna, M. P., Eds.; Fate of Turfgrass Chemicals and Pest Management Approaches; ACS Symposium Series, American Chemical Society, Washington, DC, 1999. 18. Baird, J. H.; Basta, N . T.; Huhnke, R. L.; Johnson, G. V.; Payton, M . E.; Storm, D. E.; Smolen, M . D . In: Clark, J. M.; Kenna, M . P., Eds.; Fate of Turfgrass Chemicals and Pest Management Approaches; ACS Symposium Series, American Chemical Society, Washington, DC, 1999. 19. Patty, L.; Real, B.; Grill, J. J. Pestic. Sci. 1997, 49, 243-251. 20. Reducing Dormant Spray Runoff from Orchards; Ross, L . J.; Bennett, K . P.; Kim, K. D.; Hefner, K.; Hernandez, J. State of California, Environmental Protection Agency, Department of Pesticide Regulation, Report E H 97-03, Sacramento, C A ; 1997. 21. Cohen, S. Z.; Svrjcek, Α.; Durborow, T. E.; Barnes, L . N . In: Conference Proceedings of the68 International Golf Course Conference. Golf Course Superintendents Association of America, Lawrence, K S , 1997; pp. 19-20. 22. Morioka, T.; Cho, H . S. Water Sci. Technol. 1992, 25, 77-84. 23. Hori, S.; Kato, M.; Tsukabayashi, H.; Hashiba, H . J. Environ. Chem. 1992, 2, 6570. 24. Tomimori, S.; Nagaya, Y.; Taniyama, T. Japan. J. Crop Sci. 1994, 63, 442-451. 25. Smith, A . E.; Bridges, D. C. Crop Sci. 1996, 36, 1439-1445. 26. Meyer, L . W.; Russell, D.; Louis, J. B.; Jowa, L.; Post, G.; Sanders, P. In: Pesticides in the Next Decade: The Challenges Ahead; Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, Blacksburg, V A , 1990. 27. Horst, G. L.; Shea, P. J.; Powers, W. L.; Christians, N . In: Clark, J. M.; Kenna, M. P., Eds.; Fate of Turfgrass Chemicals and Pest Management Approaches; A C S Symposium Series, American Chemical Society, Washington, D C , 1999. 28. Branham, Β. E.; Gardner, D. S.; Miltner, E. W.; Zabik, M. J. In: Clark, J. M.; Kenna, M. P., Eds.; Fate of Turfgrass Chemicals and Pest Management Approaches; ACS Symposium Series, American Chemical Society, Washington, DC, 1999. 29. Petrovic, A . M.; Lisk, D. J.; Larsson-Kovach, I. In: Clark, J. M.; Kenna, M. P., Eds.; Fate of Turfgrass Chemicals and Pest Management Approaches; A C S Symposium Series, American Chemical Society, Washington, DC, 1999. 30. Sears, M. K.; Chapman, R. A . J. Econ. Entomol. 1979, 72, 272-274. th



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Pesticides for Turfgrass Pest Management: Uses and Environmental

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