AAAS 1997 Annual Meeting
Seattle, Washington
February 16, 1996

Indicators of the Sustainability
and Impacts of Pest Management Systems

By:
Dr. Charles M. Benbrook
Dr. Edward Groth III

A necessary first step in changing the economic or environmental performance of complex systems is defining system attributes that are measurable and which can be monitored over time. In working toward sustainable patterns of agricultural resource use and food production, three major sustainability challenges have been on the global agenda for decades -- enhancing soil productivity in step with demand, efficient use of available water supplies in ways that do not cause problems down-stream, and preserving the genetic and biological diversity and integrity of farming systems.

For centuries the consequences of high rates of soil erosion and excessive use of water in agriculture have been obvious. In most countries, a variety of steps have been taken to combat these problems, at times with some success. Still, on sloping farmland, where drought is a recurrent threat, in some flood plains and wetland areas, and other fragile ecosystems, slippage in the underlying productivity of soil and water resources continues and pressure on the land is growing. In many places the sustainability of production is being undermined incrementally, despite technological advances which help maintain yields.

Our focus is on a different sort of threat to the sustainability of food and fiber production -- pests and the impacts of pest management systems. In many major farming regions, the costs, effectiveness and consequences of pest management are widely acknowledged as major worries on the farm, often second only to market volatility. Most people are not aware of the escalating annual battle most farmers are waging with weeds, bugs and plant diseases. (For a contemporary review focusing on the U.S., see Pest Management at the Crossroads, published by Consumers Union, Benbrook et al., 1996).

Rising Stakes

There is clear evidence that despite high and rising levels of reliance on pesticides in most countries and rapid innovation in the relevant sciences, pest management systems are barely keeping pace with the capacity of pests to adapt to their environment. Resistance to pesticides is a ubiquitous concern and managing resistance is a constant challenge.

Weed resistance to herbicides has taken off around the world. In several countries some weed species are resistance to herbicides in three, four or more chemical families. A rye grass species in Australia is resistant to 25 different active ingredients (Hager, 1996; Burnet et al., 1994). The first cases of resistance to the world's most widely used herbicide glyphosate (trade name, Roundup) have now been reported and many more are expected (Gressel, 1997). The proliferation of genetically engineered herbicide tolerant plants is bound to accelerate the emergence and deepen the severity of resistance to otherwise relatively low-risk herbicides like Roundup (Gressel, 1997) and the sulfonylureas (Hager, 1996; Fahnestock, 1996; Benbrook et al., 1996).

Secondary pests have now become well-established primary pests in many regions. At the same time, the pressure for tighter regulation on pesticide use is growing worldwide as progress is made in cleaning up other forms of toxic pollution, and as scientists unravel the many ways very low dose exposures may be adversely impacting human health, reproduction and development.

Three trends are converging --

In the U.S., the convergence of these trends is heightening interest in IPM in the agricultural community and food industry, among researchers, and in government. A broad-based agenda is unfolding in the public and private sectors to accelerate the transition, now well underway, from chemical-based pest management systems to those largely reliant on multitactic, biologically based interventions.

Need for New Rulers

Both marketplace and policy initiatives are struggling to overcome a common problem -- the need for better methods to measure the impacts of pesticide use, to gauge progress toward biointensive IPM, and to link IPM adoption to reductions in pesticide use and risk.

Such measures are functionally equivalent to those needed to monitor the sustainability of pest management systems, a major component of agricultural production systems. The methods we discuss herein will also find application in general studies of agricultural sustainability and farming's environmental impacts.

A. The Policy Context

Two major factors are driving recent efforts to develop a methodology to measure IPM adoption. First, the need to monitor progress in response to the Clinton Administration's 1993 IPM adoption goal -- getting 75 percent of cultivated acreage in U.S. agriculture under IPM by the year 2000; and second, the search for credible methods to support "green labeling" efforts.

In Pest Management at the Crossroads (PMAC), we discuss these and other reasons to monitor IPM adoption --

Different measurement methods will be needed to answer different questions about the performance and consequences of pest management systems. Growers are most directly in need of information on resistance, secondary pests, impacts on beneficial organisms, system cost and performance, and crop yield and quality outcomes. Consumers are more interested in the possible presence of pesticide residues in food and their drinking water, and a majority express the view in consumer surveys that they would prefer fruit and vegetables grown under systems that lessen pesticide use. Government agencies tracking and working to protect water quality in a river system would need yet another set of information and measures.

Measuring IPM adoption poses complex analytical challenges. Even relatively simple methodologies will require lots of field-specific data, some of which may be costly to obtain. Crop-pest-beneficial organism interactions are very dynamic and directly shape the nature of IPM systems and control practices needed in a given year. Hence, measurement methodologies must somehow distinguish short-term changes from longer-range shifts in pest pressure and IPM system effectiveness.

The Shortcomings of Regulation

In PMAC we concluded that regulation has done relatively little in the last 20 years to foster progress along the IPM continuum, which is not surprising given its focus on balancing pesticide risks and benefits (Benbrook et al., 1996).

The standard approach to regulation in most countries -- one product-at-a-time regulation -- periodically forces some active ingredients off the market but others have always been available to pick up the slack. The pesticides in use in the 1990s differ from those in the 1970s and 1980s. Some risks have fallen, others have risen, and some new types of risks -- like the impacts of the new, low-dose herbicides on soil microbial communities and root health -- have emerged. But all in all, little has changed in terms of overall levels of risk. As a result of most regulatory actions, the nature of risks stemming from pesticide use tends to change. As farmers shift reliance from one family of chemistry to another, it typically takes a few to several years for problems to emerge widely enough to catch the attention of regulators, and then several more for them to build a case that risks exceed benefits. In the U.S., many high-risk pesticides are commercially obsolete well before the regulatory process reaches closure.

There is now in the United States a reasonably durable baseline of pesticide risk sanctioned by current law and past regulatory actions. Implicit acceptable levels of risk can be inferred from EPA decisions, both from the perspective of single products and uses and across types of pesticides, and all pesticides collectively. There is no reason to expect this baseline to change much, although full and timely implementation of the Food Quality Protection Act of 1996 could reduce risks markedly from some classes of old pesticides. (For more information on this legislation and implementation efforts and impacts, see the Food Quality Protection Act section of the PMAC web-site, ).

For these reasons, we concluded that regulation should not be counted on to markedly reduce pesticide use and risks, and so we assessed other ways to reduce pesticide reliance and risks. We found much encouraging evidence of progress toward biointensive IPM in many major agricultural crops. Many IPM practitioners have cut their pesticide use by half or more since the late 1980s, and many have nearly or fully eliminated the need to apply broad-spectrum, ecologically disruptive pesticides. Moreover, we expect progress to accelerate as recent scientific advances are embodied in new practices, technologies and biopesticides.

The issue is no longer whether there are effective alternatives to pesticides. Today's challenge is how to lower the cost of the inputs, information and services required to make biointensive IPM cost-competitive. This challenge is particularly acute during periods of transition away from chemical-intensive systems that have greatly lowered biodiversity and the populations of key beneficials.

Economic forces also work to discourage growers from making the transition. Produce quality grading standards and associated pricing schedules are notoriously strict, often compelling farmers to make two or three late-season applications of insecticides and/or fungicides to avoid minor, cosmetic damage on peels or parts of fruit and vegetables never consumed or easily discarded. The intense competition in the pesticide industry today is placing downward pressure on the prices of older products, making it tempting for many growers to continue using them despite the availability of safer options. By lowering the cost of older products, manufacturers also raise the threshold for EPA regulatory action, since lower product costs translate directly into higher relative benefits per acre treated.

The IPM Continuum and Biointensive IPM

IPM systems exist in almost limitless variety along what can be thought of as an IPM continuum (see Chapter 7 of PMAC). Biointensive IPM systems -- the kind most people are willing to support with their food or tax dollars -- strive to lessen pest pressure through management of ecological and biological processes and interactions. When pests do emerge as a threat to crop production and quality, such systems rely principally on biological and ecological means to bring pest populations down below economic thresholds.

A strong case can be made for an increase in public and private sector investments and policy support for biointensive IPM systems because of their intrinsic public health and environmental benefits. The same case cannot be made at the chemical-intensive end of the IPM continuum. Pesticide manufacturers and others who profit from pesticide sales should bear product stewardship costs, including those needed to keep products working as well as possible. To work toward this policy principle, many countries and some states in the U.S. have taken, or are considering steps to require manufacturers and farmers to cover more of the social and regulatory costs stemming from pesticide-based systems through fees, taxes and other financial instruments.

Raising the cost of high-risk chemical based systems to more closely reflect their true social costs will help accelerate change but is just a first step. An important finding in PMAC is that the transition to biointensive IPM is likely to proceed slowly because of the lack of infrastructure needed to lower the cost and increase the reliability of biointensive IPM.

In the past, government could be counted on to supply a large portion of the investment capital needed to broaden the infrastructure supportive of a socially and economically desirable technology like biointensive IPM -- trained people, new diagnostic tools, increased emphasis on resistance to pests in plant breeding programs, weather systems and forecasting models, new ways to rear and release beneficials, and new biopesticides.

But today the drive to balance state and federal budgets, and in the U.S., general distrust of government, has diminished the public sector's role in shaping promising new areas of technology. Hence in PMAC, we offer dozens of recommendations intended to create ways for consumers to reward IPM in the marketplace, in this way incrementally expanding the demand for biointensive IPM products and services, and in this way building the infrastructure needed to support a national shift in the underpinnings of pest management systems.

Consumer surveys confirm a segment of the population is ready to respond to new products and services. A survey carried out by the Hartman Group in 1996 showed that about half the U.S. population is either currently purchasing or looking for more opportunities to purchase "earth friendly" products (Hartman, 1996). A series of questions on pesticide use and residues in food, and consumer preferences, led the Hartman Group to conclude there is a large segment of the consuming public -- as much as 30 percent of shoppers -- likely to respond favorably to the introduction of new "green labeled" food products.

While many consumers, environmentalists and taxpayers express willingness to support farmers who are making progress along the IPM continuum, the Hartman survey, among others, shows clearly that people need a personal reason to switch buying habits. Many are unaware what the term IPM stands for, and even after it is defined, only 15 percent to 25 percent of those surveyed state that they would seek out food grown using IPM. Supporting a production system is just not connected directly enough to things consumers care about to motivate changes in purchasing patterns.

But when the Hartman Group asked consumers about a food label that says "grown using IPM practices that reduce pesticide use...," the positive response rose dramatically to over 50 percent. Such results have led experts in consumer market behavior to conclude that the 30 percent to 50 percent of consumers possibly open to the purchase of "IPM-Grown" food need to be convinced that they are getting what they are willing to pay for -- reduced use and residues of risky pesticides. For this reason the ability to distinguish between pest management systems along the IPM continuum, and to link IPM adoption to pesticide reliance and risks, will be key in establishing IPM adoption baselines, in measuring progress, and distinguishing IPM-grown foods in the marketplace.

Considerable effort is underway worldwide to develop new tools to distinguish between various levels of IPM adoption, and to track pesticide reliance and risks. Much more work is needed, both in refining such methods and in compiling the data needed to credibly apply them. A major consumer education challenge lies ahead which must strive to teach the next generation of consumers what IPM is all about and why it is essential, just as today's consumer learned about recycling in the 1970s and 1980s.

We turn now to indicators of pesticide use, reliance and risk, and of IPM adoption and the methodologies required to establish baselines and monitor change. Our discussion progresses from the simplest to more complex measures. The first and always an essential task is measuring pesticide use and reliance. The data needed to do so is the foundation for also measuring changes in average pesticide risk levels. The next challenge is to characterize IPM systems along the continuum and measure where a group of growers -- sweet corn farmers in New York, apple producers in Washington -- are along it. A last, key step is to quantify the linkages between progress along the continuum and pesticide use and risks.

B. Measuring Pesticide Use and Risks

Data and indicators necessary to establish pesticide use and risk baselines, set goals and determine the effectiveness of IPM systems include –

In measuring reliance on pesticides, pounds applied is a misleading and inadequate indicator because of the profound changes in the specificity and toxicity of pesticides per pound -- or fraction of an ounce -- applied. Data on pesticide use, adjusted for toxicity, should ideally be available on a per acre basis, preferably coupled with IPM practices data on the same acre.

In general, reasonably accurate pesticide use measures are easier to develop in farming regions with a relatively high degree of homogeneity across farms and fields, since aggregate data can simply be divided by total acres planted to produce approximate estimates of per acre applications.

Use Data       A first approximation of pounds of active ingredient(s) applied per acre can be made by dividing the total pounds used in a region or country by the total acres of crops on which the pesticide is registered for use. Such information is generally accessible in all countries. Detailed and generally accurate data are available from the U.S. Department of Agriculture's "Cropping Practices Survey" databases. Recent survey data are accessible via the USDA web page (; under programs, select NASS, and go to the section on pesticide use).

Toxicity-Adjusted Measures of Use

Measures and indicators are needed to identify trends in pesticide toxicity levels within a given region and/or crop. One useful method is to rank all applied pesticides by class (herbicide, insecticide, fungicide, others), according to a given indicator of toxicity, from most toxic to least toxic. Then, average use-weighted toxicity levels can be calculated at the top end of the toxicity scale – for example, those insecticides accounting for 10 percent of total pounds applied (or 20 percent, or one-third). The same is done at the bottom end of the toxicity scale, representing the use-weighted toxicity of the least risky of the pesticides applied (as measured by a given index). These values, in turn, provide valuable insight into the distribution of risks, by assessing what we call "toxic differentials" (see Tables 3.3 and 3.4 in PMAC). The toxic differential is the difference in use-weighted toxicity levels between the least toxic and the most toxic group of pesticides accounting for some equal share of total pounds applied. In 1992, the acute toxicity differential between the top 10 percent and bottom 10 percent insecticide use groups was nearly 2,829 whereas the differential was only 27.7 in the case of herbicides and 9.3 among fungicides (Benbrook et al., 1996).

Monitoring use-weighted toxicity levels and toxic differentials over time is the simplest way we know to determine whether farmers are growing more or less reliant on high risk pesticides. At a minimum, four indicators of pesticide toxicity require attention to monitor risk levels and trends by active ingredient and type of pesticide –

Simple measures or indices of acute toxicity-adjusted pesticide use can be calculated by multiplying pounds applied per acre of individual active ingredients by LD50 values (to create an index whose value rises with increasing toxicity, we use the inverse of LD50s).

A core set of toxicological studies have been undertaken on most widely used pesticides, although many years will be required to fully evaluate existing data, and to fill data gaps. Schmidt-Bleek and Marchal carried out a review of the regulatory regimes in 22 countries, including 16 developed western countries and 6 countries in Eastern Europe at differing stages of development. They concluded that virtually all countries required comparable core acute and chronic mammalian toxicity data (Schmidt-Bleek and Marchal, 1993).

While Reference Doses and Q-Stars are useful indicators of chronic pesticide toxicity, most toxicologists believe that further data are needed to fully assess potential adverse effects arising from disruption of the endocrine system prior to and during fetal development, and during childhood (for example, see the Erice Statement). About 40 major pesticide active ingredients are known to disrupt some aspect of normal endocrine system functions (Colborn et al., 1994 and 1996; Benbrook, 1996b).

Many years will be required before improved endocrine disruptor assays and accompanying risk assessment methods are developed. Such methods must take into account multiple exposures at different stages of development, a task far more complex that the methods now used to set "safe" levels of pesticide exposure. The recently passed Food Quality Protection Act directs the U.S. EPA to develop a new battery of assays to assess a pesticide's capacity to disrupt the endocrine system, focusing both on active ingredients and so-called inert, but sometimes also toxic ingredients. This process will take several years. Positive results in such assays will probably heighten the urgency and strictness of regulatory actions, but are not expected to produce quantitative estimates of risks for many years to come.

Trends in Mammalian Toxicity Levels

Use-weighted average toxicity levels of pesticides applied is a good first-order approximation of overall levels and trends in pesticide risk. We calculated such use-weighted average acute and chronic mammalian toxicity levels by type of pesticide using data on pounds applied in the U.S. in 1971, 1982 and 1992 (see page 79 of PMAC for methodological details). Acute risk was measured by LD50s derived from the World Health Organization, and chronic toxicity was measured by a composite variable using EPA reference doses, and cancer potency factors and classifications. Values were modestly adjusted upward in our chronic toxicity algorithm in the case of pesticide active ingredients identified as endocrine disruptors (Colborn et al., 1993 and 1996).

Among the most toxic 10 percent of insecticides applied in each decade, we found that acute risks rose about four-fold between 1971 and 1992, while chronic toxicity decreased by about half. Both herbicide and fungicide chronic risk levels rose more than two-fold, while their acute risks fell marginally (Figure 3.3, Benbrook et. al., 1996).

Ecotoxicity       Work is progressing toward the development and refinement of first-order ecotoxicity risk indices. Major help in this effort has come from a recently compiled EPA ecotoxicity database (Montague, 1995). The database contains nearly 9,200 records on over 400 active ingredients, and will reach 15,000 records within a few years when all the studies required under the U.S. EPA reregistration program are entered into the database. Each record covers a single study on a test organism, and includes level of toxicity, percent of active ingredient in the test formulation, and a variety of identification codes. The availability of this database makes it possible to construct indices of ecological risks for major pesticide active ingredients. An initial set of three indices are under development

Results from applicable studies need to be synthesized into a composite measure of relative ecotoxicity per pound applied. Based on our experience and review of the EPA dataset, several different methods and composite measures will produce roughly comparable results; the same highly toxic materials stand out distinctly using many different measures or indicators. When composite variables are used, individual pesticide values will differ according to the weights assigned to different categories of studies or properties, as well as according to the way data gaps and outlier values are handled.

Impacts on Beneficial Organisms       There is limited data on impacts of pesticides on beneficial organisms. The most extensive contemporary effort to develop such indices in the U.S. was carried out by a team at Cornell University (Kovach et al., 1992). In the early 1980s, two entomologists at Oregon State University compiled a large and useful database on pesticide impacts on beneficial arthropods t hat was used, among other things, to calculate "selectivity ratios" for a range of pesticide active ingredients (see Figure 3.1 in PMAC and Theiling and Croft, 1988). Such ratios reflect the relative toxicity of a pesticide to the target pest in contrast to beneficials.

Insecticides cause by far the most serious adverse effects on most classes of beneficial organisms, both above and below the ground. There is adequate data available on most insecticides to develop an index of impacts on beneficials, which could be used as an indicator of potential to trigger secondary pests, impair pollination, or disrupt earthworms and other soil organisms that play key roles in nutrient cycling and in building soil quality.

Other concerns warrant further attention. The adverse impacts of new sulfonylurea herbicides on soil microorganisms is under active investigation. It is known that these products can reduce the effectiveness of mycorrhizzae fungi in making soil-borne phosphorous available to plant roots, and make plant roots more susceptible to a range of pathogens. Some fungicides are known to adversely impact soil microbial communities. Other potential impacts may include weakening plant immune systems through adverse impacts on systemic acquired resistance.

Adjustments for Environmental Fate and Application Methods       Physical and chemical pesticide properties and application methods clearly affect exposure -- and hence risk -- levels. The environmental fate of a pesticide determines whether potential toxicity translates into actual harm suffered. A number of basic pesticide properties play roles in environmental fate – persistence, stability, mobility in the soil, soil and water half-lives among them. As more data become available, use-weighted toxicity measures should be further adjusted for changes in environmental fate.

For the same reason, formulations, packaging, and application methods also need to be taken into account, particularly when assessing worker exposures and risk. From the beginning of the pesticide era in the 1940s through the 1960s, there was not much emphasis placed on the safe handling and application of pesticides. During the 1970s and into the 1980s, major strides were made in reducing applicator exposure through a variety of changes in pesticide products and application methods. Since the mid-1980s such changes have contributed to incremental, but relatively modest reductions in exposure.

Dealing with Limited Data

Given that data on practices and pesticide use and risks will always be incomplete, a number of short-cuts, proxy variables, and analytical techniques must be developed in estimating indicators of pesticide risk trends and IPM adoption. The greater the variability within a region in cropping patterns and technology, pest pressure and IPM systems, the more difficult it will be to develop an accurate assessment of the IPM system adoption along the continuum.

One necessary step is defining the scope of study sharply and in response to the major concerns with pest management systems and/or pesticide use. Wherever major changes are occurring in land use patterns, farming systems, or pesticide use, it is important to pay attention to what is happening with IPM systems. Indicators that should be monitored include --

C. Measuring IPM Adoption

Integrated pest management systems exist along a continuum and range from "no" or "low" levels of adoption to "medium" and "high," or biointensive IPM. Biointensive IPM systems are characterized by a preponderance of biologically based preventive practices and strategies that limit the need for pesticide applications.

Data on field level pest management practices, coupled with pesticide use data are required to apply the IPM measurement methodology set forth in PMAC (see also an empirical application done for World Wildlife Fund, Benbrook, 1996a). Three variables are calculated –

Data on individual fields encompassing both pesticide use and IPM practices are required to apply this methodology. Once acreage producing a given crop is divided into the four zones along the IPM continuum, it is relatively simple to compare costs and yields, pesticide reliance, use and risks across representative pest management systems in each of the zones. It is also often simple to recognize the practices and tactics adopted by farmers as they move from one zone to the next -- a key in setting R+D and education priorities.

Our methodology for measuring IPM adoption requires extensive data, particularly in complex pest management systems involving dozens of preventive practices and highly variable levels of pest pressure. In general, the pesticide use data needed to calculate DAATs is always available from one or more sources -- one-half the analytical challenge. Since 1994, farmers have been required to keep such records to comply with new worker-protection standards. Some states require full use-reporting, and others are moving steadily in this direction.

It is a much more challenging task to identify preventive practices, assign points to them, and collect the needed data on practice adoption on sample farms. Several researcher groups and programs have taken on this task and are working on ways to facilitate the process of data collection and management. In order to develop estimates of IPM adoption in the absence of complete data, several analytical short-cuts can be used to develop approximate values and estimates.

Practice- and Point-Based Systems

The USDA's first attempt to measure IPM adoption was based on use of practices deemed "indicative of an IPM approach" (Vandeman et al., 1994). With a few exceptions, any acre on which pests were scouted and pesticides applied in accord with thresholds was deemed under at least "low level" IPM. As more practices were adopted -- like cultivation for weed control, assaying the soil for pathogens, rotations, and releases of beneficial organisms -- fields were judged to be under "medium" level (one or two additional practices) or "high" level IPM (three or more additional practices). Using its methods and data from the early 1990s, the USDA concluded that about half of the nation's cropland acreage was managed using some level of IPM.

We critique USDA's pioneering effort in PMAC and recommend a number of refinements, some of which USDA is now working to incorporate in future estimates of IPM adoption. Other groups have used a comparable "count the practices" approach in measuring IPM adoption.

Such methods have significant shortcomings. They fail to take into account variable levels of pest pressure, and provide little help in quantifying the linkages between IPM systems and pesticide use. Several groups since have built on the USDA's first effort by creating point-based systems, including the Massachusetts Department of Agriculture's "Partners with Nature" program, the Cornell-Wegman's New York IPM-grown labeling program, the "Eco-O.K." program run by the Rainforest Alliance, and a system developed by the National Potato Council.

In general, point-based systems identify a taxonomy of practices believed to represent state-of-the-art IPM and assign points to each practice reflecting its relative value in reducing pest pressure and losses. To some extent, the difficulty and cost of various practices are generally taken into account in assigning point values. Growers are considered using IPM if they use some threshold percentage of the total points possible across all identified practices. In the case of Massachusetts "Partners with Nature" program, potato growers must have 70 percent of possible points. Under the Cornell-New York sweet corn IPM program, growers must attain 120 of 150 possible points, or 80 percent.

While a major improvement over systems that just count practices, systems based just on points-attained do not take into account actual levels of pesticide use, nor do they capture whether using IPM practices leads to significantly less pesticide than not using the practices. Another problem with such systems is that they are biased against farmers who use organic systems, complex rotations or other unusual methods to keep pests at very low levels. Because such farmers are not likely to need, and hence do not use many of the practices surveyed in a "count the practices" or point-based system, they might be deemed as not practicing IPM, when in fact they are well into the biointensive IPM zone along the continuum where they no longer have nearly as much pest pressure to contend with on an annual basis.

In addition, these systems do not capture to any significant degree the necessary adaptations farmers must make from year to year when pest populations unexpectedly explode -- or never build. These system shortcomings are recognized by the sponsoring organizations and efforts are underway to supplement the systems with additional records and measures that capture the linkages between IPM and pesticide use, and the need for IPM systems to change as a function of abrupt changes in pest pressure, often a weather-driven phenomenon.

"Leading Indicator" Practices

Another strategy is being investigated by some organizations -- focusing on a single or few "leading indicators" of biointensive IPM systems. For example, the codling moth is the dominant insect pest plaguing apple and pear growers worldwide, and insect pest management systems for these orchard crops are largely dictated by and built around the management of this pest. Monitoring change in codling moth management strategies that provides valuable insight into pear/apple insect pest management systems.

Sometimes there is both a leading pest like codling moth, and a "leading indicator" biointensive IPM practice. Pheromone-based codling moth mating disruption (CMMD) is clearly now a "leading indicator" of biointensive IPM systems in apple and pear production both in the U.S. and abroad. While used on just a few percent of Washington state apples three years ago, experts anticipate that up to 15 percent of the state's apple acreage will be under CMMD this summer.

Other potential "leading indicators" of biointensive IPM include --

Use of these practices would typically result in high PPP values and would also tend to be found on farms where use of toxic, broad-spectrum materials is avoided under most circumstances. Hence, there is often a correlation between high PPP values and relatively low DAAT values, producing the high IPM System Ratio values found on farms in the biointensive zone along the continuum.

Other practices are equally reliable "leading indicators" of chemical-intensive systems and lack of progress along the IPM continuum. Pre-plant fumigation of annual crops with a broad-spectrum biocide like methyl bromide, or the soil fumigant metam-sodium, is an obvious example, as is several applications of broad-spectrum insecticides.

Identification of "leading indicators" of biointensive and/or chemical-intensive IPM systems can greatly simplify the data gathering and analytical methods required to monitor change in pest management systems. Caution must be exercised, however, to assure that such leading indicators reflect contemporary changes in pest pressure and pest management systems and technologies.

Knowledge and Information-Based Systems

In high-value fruit and vegetable cropping systems, there is often intense pest pressure and a high premium on avoiding risk of pest losses. In such places, IPM systems and pesticide use patterns can be extraordinarily complex and dynamic. Any measurement system based on practice adoption and pesticide use, and linkages between the two, will require a small mountain of information, and every year. Short-cuts will be required but will also limit the applicability and reliability of such systems. And so, alternative approaches may be needed and several are under exploration.

A common strategy is emerging that entails focus on the information and knowledge relied on in reaching a decision to use certain seminal practices, rather than the number of practices used. This approach is under development as a component within IPM-labeling efforts, including those sponsored by the World Wildlife Fund-Wisconsin Potato and Vegetable Growers Association partnership, the Food Alliance in the Northwest, and as part of the Mothers and Others "Core Values" apple program in New England. (For details on these programs, see the "Measuring IPM Adoption" portion of the PMAC web page, ).

This knowledge-based strategy is related to the "leading indicator" approach discussed above, but augments it through a set of questions linked to seminal pest management system choices. The questions are designed to identify the completeness of the information growers had when deciding what practices to adopt, as well as how they used the information in structuring and carrying out field interventions -- whether applying a pesticide, a cultural practice, releasing beneficials, or doing nothing.

As an example, consider a common dilemma -- whether to spray a broad-spectrum insecticide in the face of an early season leafminer, thrips or aphid infestation, knowing that the application will set off a number of other secondary pests because of impacts on their natural enemies. Sometimes such applications, or other costly interventions, simply cannot be avoided, but in other cases they can and should be.

In addition, such potentially costly interventions need to be implemented with great care to minimize secondary pest problems, emergence of resistance or other problems. In some situations, growers need to take into account spatial factors, like the location of beneficial organism habitat, or temporal factors like when beneficials are not moving about and therefor least likely to be impacted by a spray.

A grower's commitment to IPM, and the sophistication of his or her system, is going to be most readily apparent from a review of the decision-process and outcome in such high-risk, high-impact situations. Hence, an IPM measurement methodology could be based in large part on annual assessment of three to five such seminal components of a pest management system, comparing the information and knowledge each grower within an area relies on, and what conclusions they reach and actions they take in response to the information in hand.

In summary, for each such pest management challenge, growers or pest management specialists could be asked three sets of questions --

Dealing with Unusual Circumstances

In discussions with several growers and pest management experts applying the PMAC IPM measurement method, a common concern is how to account for unexpected, often sudden and unavoidable pest problems. Recent examples in the U.S. include newly established pests like Thrips palmi in Florida or white flies through the southwest, or the aggressive, hard-to-control strain of late blight in potato production. The relatively sudden proliferation of Bt-transgenic plant varieties, and the inevitability of resistance, is a technology-based example.

Facing such problems, growers often have no time to implement biologically based control alternatives, and have to increase the intensity of spraying in order to avoid major losses. An IPM measurement methodology should avoid allowing the increased pesticide use necessitated by such circumstances to drive a committed IPM producer back into the "no" or "low" zone along the IPM continuum.

Two strategies are being developed to preclude this from happening, while also not opening the door so wide that relatively heavy reliance on conventional pesticides becomes possible even in the biointensive zone of the IPM continuum. A key notion behind our measurement methodology is that any increase in pest pressure which necessitates a short-term increase in pesticide use should be countered by a roughly analogous increase in the scope, and hopefully effectiveness of preventive practices. Hence, in calculating IPM system ratio values, it may be appropriate to count both increased pesticide DAATs (dose adjusted acre-treatments) and associated increases in PPPs (preventive practice points) in the same year, even though some of the preventive practices may not be taken until the following season.

A second approach is being used in some measurement projects. In situations where pest pressure forces a significant increase in pesticide use, an additional set of questions can be asked assessing the information and knowledge base relied upon prior to taking control actions. Preventive practice points roughly comparable to the DAATs incurred could be assigned in instances where growers and pest managers do everything conceivably possible to avoid increased pesticide use, and also take all available precautions to avoid secondary pest problems, resistance and adverse environmental or worker-safety outcomes.

No such extra points, or fewer points, would be assigned after more than two years, at which point growers would be expected to implement additional preventive practices to avoid slipping backwards along the IPM continuum. In reality, such slippage is going to occur, and where it is identified, it will send a clear signal to researchers and the private sector to accelerate the search for new biointensive IPM alternatives.

A last advantage of knowledge-based systems is worth noting. Measuring IPM adoption is going to take effort and cost money, particularly if verifiable systems are used to support IPM-labeling programs that become important, value-added factors in competitive markets. Those designing and implementing such systems should do everything possible to keep system costs down and to design approaches that serve as many useful ends as possible.

Knowledge-based systems can do just that by also serving as a key tool fostering grower-scientist-practitioner dialog on the cutting edge of IPM implementation in the field. The pest management issues to focus on each year in such systems, and the information and decision-support questions addressed, will all be identified collaboratively by growers, consultants and researchers. The questions asked each year of participating farmers will help direct attention to scouting techniques, ecological interactions, the nuances of emerging tools and biopesticides, and ways to make better use of decision-support tools and other sources of information.

At the end of each season during grower meetings, the results of the past season are routinely reviewed. Growers or others who feel they have found a better way to deal with a common pest problem will be free to make their case. The resulting exchanges among growers, consultants and researchers will quickly highlight where there is consensus, in contrast to where further research and experimentation are needed in the field. In this way, a knowledge-based system can serve both as an IPM measurement and verification tool, and as a key process fostering dialog and creative, collective problem solving.

Conclusions

The data and methods needed to track pesticide use and risks in the context of measuring IPM adoption are essentially the same as those needed to develop and track several key indicators of the sustainability of pest management systems. There are ample pesticide use data available for major crops, reliable to the state level. A number of useful indicators are relatively easy to calculate from available data.

Accessible use data can be translated into first-order approximations of trends in use-weighted pesticide toxicity and risks. Since the differences in relative risk levels are so enormous across registered pesticides, and the nature and levels of pesticide risks have changed so much over the years, even relatively crude methods produce a reasonably useful picture of pesticide risk levels and trends. Even simple methods will produce reasonably reliable identification of pesticides that pose risks an order of magnitude higher than average, as well as those posing risks an order of magnitude less than the norm. The policy relevance is obvious, since this ability allows us to monitor whether reliance is rising or falling on high risk/low risk pesticides.

Current methods cannot be trusted, however, in trying to distinguish between the specific or overall risks associated with closely related active ingredients in several chemical families, or near the mid-point in the distribution of risk levels. Even with much more data, state-of-the-art exposure and risk assessment tools, and years of effort, EPA can not make such determinations reliably between many of even the most widely used and studied pesticides.

The trickiest challenge in measuring IPM adoption is capturing the interplay between pest pressure, preventive practices, and pesticide use. Measurement methods must somehow take all three factors into account -- particularly how abrupt changes in pest pressure can change both pesticide use and the need for preventive practices. Methods to do so are reviewed.

Current USDA science and education programs and investments, as well as other government policies, are dedicated to supporting progress along the IPM continuum. There is an unmet need for credible methods to monitor progress so that the costs and benefits of different approaches and policies to support IPM can be evaluated. Likewise, a number of private organizations and companies are offering IPM-grown, "green-labeled" foods in the marketplace, or are moving toward this goal rapidly. Some skeptics and critics of this approach are already questioning what these labels really mean.

Consumer surveys show that a strong and positive response in the market will depend upon convincing consumers that there is a direct linkage between IPM adoption and pesticide use and risk reduction. Our research shows that the marketplace must shoulder the major burden in generating the income and investment capital needed to broaden the infrastructure supportive of economical, reliable biointensive IPM systems. Hence the emphasis consumer and environmental groups, the USDA and EPA, and others now place on moving forward in the measurement arena.

There is also high and rising interest in methods to measure IPM adoption and link it to changes in pesticide use and risks. The methods to do so are essentially the same any analyst will need in crafting indicators of the sustainability of the pest management component of agricultural systems. Much work is needed, as are ways for analysts and researchers to collaborate and share results. One method to do so is suggested in the PMAC web page in the "Measuring IPM Adoption" section, under "A Proposal." We look forward to your thoughts and suggestions, and appreciate the kind invitation to join this symposium panel.

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