Northeast Region IPM Grants
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Project Title:
| States: | New York |
| Project Directors: | Daniel Peck |
| Institutions: | Cornell University |
| Project Type: | Research - Critical Step |
| Award*: | $ 15,000 |
| Term: | 12 months |
| Setting: |
Turf |
*Award shown is total amount to be used over the course of the project term.
White grubs are the most widespread and damaging pests in turfgrass habitats of the Northeast. In this extensive and rapidly expanding component of our urban and rural landscapes, management is highly dependent on chemical pesticides. Ten insecticides once offered a variety of control options, but only two preventive (counter to sound IPM) and one curative option (under FQPA review) still exist. Insecticide applications for grubs can be avoided 80% of the time by using sampling as a decision-making tool. Alternative biological control options are limited and largely non-efficacious. Advancing biologically-based pest management in this system may depend on the tactical combination of biological and chemical controls. This opportunity is based on recent investigations showing increased efficacy of biocontrols when insects are challenged by other stressors, such as reduced rates of preventive insecticides. The driving need is based on providing new curative options to replace preventive applications and thereby improve IPM. To seriously evaluate this approach, we will test a range of biologicals - singly and in combination with insecticide synergists - to control white grubs. These detailed laboratory studies will identify the most promising products and synergistic combinations for continued studies, and measure how efficacy varies across different white grub species. In this “critical step” research, we anticipate finding one or more truly synergistic combinations that will open the door for biologically-based curative control options. Documenting this new approach will help guide the development of biologically-based pest management options for soil insect pests in other turfgrass and horticultural systems.
Project PurposeThe purpose of this project is to reduce the economic and environmental costs of insecticide dependence in turfgrass systems by evaluating and promoting new approaches to pest management.
Overall Objective
The main objective of this project is to evaluate and promote biologically-based management options for white grubs in turfgrass, with an emphasis on the synergistic interaction between combined biological and chemical control products.
Specific Objectives
· Screen the efficacy of 15 different registered and experimental bioproducts and curative chemical insecticides to larvae of European chafer in controlled laboratory bioassays.
· Quantify and compare the efficacy of the same products to four white grub species: European chafer, Japanese beetle, Oriental beetle and Asiatic garden beetle.
· Evaluate and compare the efficacy of different combinations of select bioproducts with three rates of curative chemical insecticides to larvae of European chafer in controlled laboratory bioassays.
· Quantify and compare the efficacy of select chemical/biological combinations to four white grub species: European chafer, Japanese beetle, Oriental beetle and Asiatic garden beetle.
· Identify the most promising combinations for future greenhouse and field trials by characterizing the interactions as synergistic, additive or antagonistic, and ranking their efficacy and compatibility.
Introduction
Current white grub control scenarios in turfgrass of the Northeast have essentially closed the door to successful IPM. Not only is there widespread reliance on early season preventive applications of imidacloprid, there is a lack of biologically-based control alternatives. In practical terms this means that turfgrass managers have no quantitative way to decide when not to spray, other than making localized applications that target areas highly susceptible or traditionally affected by these pest. And those seeking non-chemical options are stymied by biological alternatives that are relatively difficult or expensive to apply, or yield such inconsistent results that they are impracticable. Part of the solution are curative alternatives that would permit sampling and better decision-making, and biological alternatives that could supplant reliance on chemical insecticides.
Among white grubs and other soil-borne insect pests, there is broadening evidence that synergistic interactions between chemical and biological insecticides hold promise for new management opportunities. For instance, separate laboratory studies have shown that the susceptibility of white grubs to entomopathogenic nematodes can be enhanced by other stressors, including endophyte infection of the host plant, Bt (Bacillus thuringiensis) and milky spore disease (Paenibacillus popilliae) application, and the insecticide imidacloprid. This suggests that there is promise in carefully evaluating and exploiting the susceptibility of insects to control tactics while they are being challenged under other conditions.
To date, however, this approach has not been undertaken in a comprehensive fashion for any turfgrass pest, nor has it been adapted to or evaluated under field conditions. The “critical step” we propose to take in this proposal, is to conduct a series of laboratory bioassays that will launch a systematic and cohesive approach to advance biologically-based management in turfgrass systems. Results from these detailed laboratory studies will guide greenhouse and field studies, and in turn integration of new approaches into existing management scenarios. In essence, we seek to understand under what circumstances biologically-based pest management can be effective, whether those conditions are widespread or reproducible, and how to overcome the limits to adoption of these technologies. We will end up with the best recommendations for how synergisms between combined chemical and biological control products can be exploited and best incorporated into IPM programs for white grubs and other troublesome soil insect pests.
Scope of the Problem
Turfgrass is a valuable and rapidly expanding component of our urban and rural landscape. In 1990, it was estimated that turfgrass covered 12 million hectares in the U.S. (Potter & Braman 1991) and today that includes 60 million lawns and 16,000 golf courses (Emmons 2000). In NY, the estimated expenditure of the turfgrass industry two decades ago was $1 billion (Gruttadaurio et al. 1982). The NY Agricultural Statistics Survey has just published results compiled from a 2003 statewide survey revealing that this industry has ballooned to $5.1 billion annually for the maintenance of 3.43 million acres (NASS 2004). In addition to its significant economic contribution, turfgrass provides important recreational, ecological and visual functions in our society. Recreational uses include lawns around homes, businesses and institutions, athletic fields, golf courses and parks. Ecological roles include soil stabilization, erosion control, reduction and filtering of runoff, and cooling of the local atmosphere - especially in urban areas. Turfgrass is visually pleasing as an alternative to concrete or pavement in urban and suburban areas, and provides textural contrast in rural and otherwise vegetated areas.
As managed ecosystems, these extensive and diverse turfgrass habitats require decision-making strategies to maintain them for their intended uses. To IPM practitioners, better management of pests and diseases across this area and over this sector means opportunities for great gains in the improvement of human and environmental health and welfare.
White grub species are the most injurious and widespread pest complex in turfgrass of the U.S. (Vittum et al. 1999). In the Northeast, four of the eight species are introduced exotics, including the Asiatic garden beetle, European chafer, Japanese beetle and Oriental beetle. Since its introduction in 1917 (NJ) the Japanese beetle has expanded its range to the Mississippi and beyond (Alsopp 1996); it is currently one of the most ubiquitous and injurious pests of turfgrass and ornamentals in the eastern U.S., resulting in economic losses of >$460 million/year (USDA-Aphis 1998). California deploys some 10,000 traps annually in their Japanese beetle monitoring and detection program as part of efforts to prevent Japanese beetle establishment on the West Coast; this complements the U.S. Domestic Japanese Beetle Harmonization Plan that regulates the movement of nursery plants from infested to non-infested states (Klein et al. 2002).
Our focus on white grub control in turfgrass thereby represents the major pest complex in one of the most extensive and rapidly expanding components of our urban and rural landscape. Better managing this vast area will have huge positive impacts especially considering that this habitat is intimately associated with human populations and that home owners can spray lawn chemicals with little regulation. Under this scenario, our modern challenge is not to promote more conversion of wild and agricultural lands to turfgrass, but to better protect and steward the land already dedicated to that use.
At least in the Northeast, current white grub management scenarios have essentially closed the door to successful IPM because of dependence on early season preventive applications of imidacloprid (Merit). This neonicotinoid pesticide has largely replaced several other insecticides that were less effective, had higher mammalian toxicity, were withdrawn from registration, or are currently under FQPA review. Imidacloprid is not effective against late instar grubs yet early instars are too difficult to target in sampling programs. As a result, imidacloprid is applied early in the season before sampling can assess thresholds. On Long Island, NY, where local legislation has severely curtailed the use of certain insecticides, imidacloprid has now been detected in groundwater, sparking discussion about best management practices for its continued use (Gilrein & Yeh 2004). Best management practices should discourage wall-to-wall applications and promote localized treatments that target areas highly susceptible or traditionally affected by this pest (Rossi 2003).
In addition to dwindling chemical control options, the practice of IPM is also compromised by lack of biologically-based control alternatives. Many natural enemies have been studied, and a few have been commercialized, but no real non-pesticide options are available with proven effectiveness and practicality for white grubs in turfgrass. The major commercial products, based on entomopathogenic nematodes and Paenibacillus popilliae (the causal agent of milky disease), are generally regarded as ineffective or too costly for any real role in white grub management. Overall, IPM of white grubs in turfgrass would benefit immensely from (i) curative alternatives that would permit sampling and better decision-making, and (ii) biological alternatives that could supplant reliance on chemical insecticides.
Background
White grub biology and ecology
White grubs are the immature stages of scarab beetles (Coleoptera: Scarabaeidae) and are among the most important soil insect pests found in U.S. and international agriculture (Jackson & Glare 1992, Vittum et al. 1999, Bellotti & Peck 2000). In the northeastern U.S., turfgrass is subject to intense feeding pressure from a complex of at least eight scarab species. These include four native and four introduced species (Table 1). This pest complex is very widespread throughout the region although the distribution of each particular species is limited by geography and local site conditions.
Table 1. White grub pests of turfgrass in the northeastern U.S.
Common Name Scientific Name Origin Asiatic garden beetle Maladera castanea Exotic Black turfgrass ataenius Ataenius spretulus Native European chafer Rhizotrogus majalis Exotic Green June beetle Cotinis nitida Native Japanese beetle Popillia japonica Exotic May and June beetles Phyllophaga spp Native Northern masked chafers Cyclocephala borealis Native Oriental beetle Exomala orientalis Exotic With two exceptions, these white grubs have a one-year life cycle in the Northeast. The black turfgrass ataenius completes one to two generations per year, while May or June beetles require one to three years to complete a generation. The life cycle varies slightly depending on species, geographic location, and seasonal weather. Typically, eggs are laid in late June or early July, and grubs hatch in late July or early August. Larvae feed on grass roots, weakening individual plants. As grubs persist and grow larger in the late summer and fall, more roots are consumed and individual grass plants die. Low to moderate levels of grub infestation can thin turf stands, whereas high populations (>100 grubs/m2) usually result in large patches of dead turf. Severe damage is common, and entire lawns, athletic fields and golf course fairways can be rendered unusable. Damaged turf peels back easily from the soil (often when raking) because the root systems have been disrupted or devoured. The soil surface will feel spongy, not firm. Unlike other species, larvae of the green June beetle cause damage by their active tunneling through the root zone, not by direct feeding on roots.
Because the Japanese beetle is a high-profile and abundant pest throughout the Northeast, many products and practices for white grub management have only targeted this species. However, the Japanese beetle has been displaced as the most damaging scarab pest in turf in many areas on a local or regional basis. For example, the European chafer is the predominant insect pest of lawns across much of upstate NY and is expanding its impact into MA and NH. The European chafer is considered the most difficult of all grubs to control using traditional insecticides and biological control agents, and is more damaging to turf than the Japanese beetle. Oriental beetles have become the predominant pest in some areas, and have spread throughout the Northeast (Alm et al. 1999). Other species such as the Asiatic garden beetle, northern masked chafer, green June beetle and Phyllophaga beetles are increasing in importance as well.
Insecticide history and management
Traditionally, turf care specialists manage scarab grubs with one or two annual insecticide applications. They seldom assess grub population levels and species composition before making treatment decisions, and usually apply insecticides preventively or in direct response to turf damage. Prophylactic treatments have increased tremendously since the introduction of imidacloprid (which is applied before beetles oviposit and grub populations can be assessed), and the loss of several curative compounds.
As recently as five years ago, at least ten insecticides were labeled for use against white grubs. Those included bendiocarb, carbaryl, chlorpyrifos, diazinon, ethoprop, fonofos, halofenozide, imidacloprid, isofenphos and trichlorfon. The wide array of products varied in their speed of efficacy, persistence, species-specific efficacy, ability to penetrate the thatch layer, and a variety of environmental impact factors. Choice is important in grub control products because of the long duration of the damaging stage of the insect (>3 months), the variety of grub species that may be encountered, and the diversity of sites and settings where grubs are pests. However, options are now limited because many of the previously available insecticides have been eliminated or severely restricted from the turf market, as a direct result of FQPA.
Several materials were voluntarily removed from the turf market (e.g., bendiocarb, ethoprop, fonofos and isofenphos) within the last four years. These materials became effective within three to six days after application and provided residual activity for three to six weeks. Comparable curative compounds of intermediate speed of efficacy and persistence are no longer available.
Additional restrictions have resulted from label changes that significantly reduced application rates to ineffective levels for grub control, thereby functionally removing more insecticides from the turf market (e.g. diazinon and chlorpyrifos). Of the remaining compounds, carbaryl and trichlorfon are in the group of cholinesterase inhibitors that is still undergoing review, and they may eventually be removed from the turf market as well. Carbaryl has been inconsistent at best when used against white grubs (Shetlar 1995), but trichlorfon is a critical part of any integrated pest management system, because it is the only fast-acting material remaining that can be used to reduce grub populations after damage becomes apparent (Heller & Walker 2000, Vittum et al. 2000a).
Throughout the 1990s, turf managers had many options when facing the need to manage a white grub infestation. They had access to materials that would take a couple weeks to become active but remained effective for three to five months (e.g. imidacloprid), intermediate materials as described above, or fast-acting compounds that would degrade within a few weeks after application. But since FQPA was promulgated, the list has dwindled to one curative fast-acting material and two products that are most effective when applied preventively (imidacloprid and halofenozide). The application of preventive materials before sampling to assess damage potential is counter to good IPM practices, but is chosen by many managers now because of the lack of options.
To further complicate matters, the eight important pest species of grubs occurring in the Northeast vary widely in their susceptibility to insecticides (Alm et al. 1999). For example, halofenozide (an insect growth regulator) is effective against Japanese beetles, but not against Oriental beetles and European chafers (Cowles & Villani 1996) that predominate in many parts of southern New England and NY. Therefore, many turf managers hesitate to use halofenozide, even though it is much less toxic to vertebrates and poses fewer problems in the environment than the curative option (trichlorfon) (Cowles & Villani 1996, Vittum et al. 2000b).
Coupling the direct loss of insecticides (as a result of FQPA decisions) with the complications of multiple grub species, the investigation of non-chemical alternatives for grub management is critical.
Biological and cultural management
Among professional turf managers, prophylactic treatments predominate despite extensive multiyear research showing that insecticide treatment is only warranted 20% of the time on both lawns and golf courses in NY (Grant 1995, Nyrop et al. 1995, Grant et al. 1996). Therefore, insecticide applications directed at scarab grubs in turfgrass could be greatly reduced if turfgrass managers learned and implemented sampling plans. Scarab grub sampling has been shown to be an economical and efficient decision tool for determining the need for treatment of scarab grubs in turf.
Biological control options are highly sought by homeowners as well as professionals who manage lawns, school grounds, parks, athletic fields and golf courses. However, currently available biological controls for scarab grubs are extremely inconsistent in their results and vary greatly by target species. The two major biological control agents commercially available for management of white grubs in turf are entomopathogenic nematodes and the bacteria that cause milky spore disease.
Entomopathogenic nematodes have proven to be one of the most successful biological strategies, often providing control comparable to insecticide treatments when environmental conditions were ideal (Shetlar et al. 1988, Klein 1990, Shanks & Agudelo-Silva 1990, Georgis & Gaugler 1991, Kaya et al. 1993, Gaugler 1999). However, there has been great variability in efficacy based on biotic factors such as matching nematode strains with the appropriate target species (Gaugler 1999) and abiotic factors such as soil moisture and temperature (Koppenhöfer et al. 1995, Fujiie et al. 1996, Grant 2001).
Milky spore disease powder is produced by grinding up living, diseased Japanese beetle grubs infected with the bacterial complex Paenibacillus popilliae and P. lentimorbus (formerly known as Bacillus). The bacterial population can build up over several years to become suppressive to Japanese beetle grubs but only if very high populations of the grubs are tolerated. Commercial preparations of milky spore powder have performed poorly in recent tests, leading to questions about the usefulness of this biological control agent for white grub management (Redmond & Potter 1995, Koppenhöfer et al. 2000a, DCP unpublished data). Many formulations applied according to conventional procedures are not efficacious in the field. Another limitation is that the bacteria is most infective to Japanese beetle grubs and of no value against other common grub species infesting turfgrass in the Northeast. Finally, because milky disease bacteria only multiplies within living bodies of grubs, one must be willing to tolerate a period of relatively high grub populations to obtain disease levels sufficient to control grubs.
New Opportunities for Biologicals
We feel that new opportunities for biologically-based management of white grubs in turfgrass are on the horizon. First, new products are still being actively developed by the commercial sector, and these require rigorous laboratory and field testing to gauge their potential. Measuring that potential should not overlook how effective the product is across different turfgrass management systems and across the variety of white grub species that pose problems.
Second, there is new broad evidence from the scientific literature that synergisms between chemical and biological agents is a promising approach for management of soil insects and turfgrass pests. For example, third instar white grubs are more susceptible to nematodes when challenged by reduced rates of imidacloprid or by endophytic host plants (Grewal et al. 1995, Koppenhöfer & Kaya 1998, Koppenhöfer et al. 2000b, Koppenhöfer & Fuzy 2003a). Neither imidacloprid, endophytes nor nematodes alone are efficaceous against this robust life stage. In addition, other studies have confirmed that reduced rates of imidacloprid can enhance pathogenicity of fungal entomopathogens in other beetle larvae such as root weevils and Colorado potato beetle (Quintela & McCoy 1998, Furlong & Groden 2001). This justifies the need to evaluate how combined approaches could open curative options for white grub management.
Third, there is an increasing demand for more limited use of chemical pesticides in turfgrass systems. This means that we need to understand under what circumstances biologically-based pest management can be effective, whether those conditions are widespread or reproducible, and how to overcome the limits to adoption of these technologies. A major point of entry is to systematically investigate the additive and synergistic effects of combined control tactics, such as reduced rates of pesticides in tandem with biologicals. Limiting the economic and environmental costs of pesticides may depend on new management approaches such as this.
Although the barriers to biologically-based pest management in turfgrass may be formidable at present, there is most certainly a potential for future implementation. This potential is based on aggressive pesticide regulation in certain counties of NY, demand for reduced-pesticide control alternatives by stakeholders, and the high value and management intensity of the affected commodity. The white grub system thereby offers an opportunity for serious scrutiny and evaluation of alternative approaches, warranting a comprehensive analysis of how control tactics can be combined, and how synergisms could be exploited, to achieve more effective pest management while reducing our reliance on chemical insecticides.
Relationship to Stakeholder Priorities
In the Northeast, scarab grubs are the primary insect pests of turfgrass (Vittum et al. 1999) and are of particular concern in lawn, golf course and athletic field turf. As soil insect pests, white grubs are particularly troublesome because of how difficult it is to monitor, interpret and manipulate interactions that are being played out below the soil surface. Compared to above-ground foliar feeding insects, below-ground root feeding insects are harder to sample and the products used to control them are harder to accurately deliver. Another challenge is the number of exotic pests species. Unintentionally introduced to the Northeast, these species have arrived without the natural enemies, competitors or other factors that might have checked populations in their native regions. Therefore they have a great capacity to outbreak and cause highly damaging infestations. In addition to their species diversity, and widespread distribution, these reasons are why white grubs are overwhelmingly considered by stakeholders to be the most injurious pests in turfgrass of the Northeast.
The 2003 New York Turfgrass Survey is the most recent statewide survey in the Northeast to assess the value of this industry (NASS 2004). In this report, data are compiled that show total annual expenditures for insecticides exceeding $12.7 million, the majority of this attributed to the activities of lawn care professionals (Table 2). Across major turfgrass areas, 15-40% of respondents regarded insect pests as a leading problem in turf management.
Table 2. Importance of insect pests and their control in turfgrass of NY (NASS 2004).
Golf Courses Sod Lawn Care Schools Proportion of turf maintenance expenses for insecticides 5.8% 6.0% 11.6% 0.6% Total expense for insecticides $3,653,111 $143,640 $8,876,088 $51,719 Respondents reporting insects as leading problem in turf 15% 40% 24% 10% The Northeast Working Group on IPM for Golf listed seven research priorities that must be addressed in order to improve and expand implementation of IPM on golf courses in the Northeast region (http://northeastipm.org/priorities/Priorities-GolfIPMWG-2001.pdf). Of the four highest ranking, one was “Alternatives to current pesticides including new (non-pesticide) IPM techniques,” an area directly addressed by our proposed study. This group met in January 2001, and was a broad-based group of participants interested in golf course IPM, including superintendents, university personnel, environmental and public health advocates, and representatives from the US Golf Association and the US EPA.
In the National Roadmap for Integrated Pest Management (May 17, 2004) prepared by stakeholders across the nation (http://northeastipm.org/regu_regional.cfm), residential and public areas is listed as one of three IPM focus areas. Turfgrass systems are more intimately associated with where people “live, work, and play” than any agricultural commodity. Therefore expanding and improving IPM programs in these managed habitats will contribute to overall human and environmental health. Our studies also directly address one of the report’s three Future Directions, “Minimize adverse environmental effects from pest and related management strategies.” Among the eight research needs listed for the national IPM Program, our studies address “Develop new generation low-risk suppression tactics including biological control and products of traditional breeding and biotechnology.”
The “Survey of Current Pest Management Practices of New York State Schools” was developed as a collaborative effort among the NY State Department of Health, NY State Department of Education, and the NY State IPM Program (http://www.nysipm.cornell.edu/comm/school.pdf). From results published in 2004, statewide an average of 17% of the districts cited white grubs in school grounds and athletic fields as one of their most frequent pest problems, and 10% said grubs were among the most troublesome. The greatest concern about grubs was expressed on Long Island, where 31% of schools cited grubs as a frequent problem, and 16% as a very troublesome problem.
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