An Appraisal of EPA s Assessment of the Benefits of Bt Crops

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1 An Appraisal of EPA s Assessment of the Benefits of Bt Crops A. Benefits of Bt-Field Corn By: Dr. Charles M. Benbrook Benbrook Consulting Services Prepared For: The Union of Concerned Scientists October 17, 2000 SUMMARY On the basis of its benefits assessment, EPA concludes that adoption of Bt corn has increased yields and reduced insecticide applications targeting the European corn borer (ECB). Furthermore, the agency estimates net benefits to farmers in 1999 of $65.4 million, based on average net benefits of $3.31 per acre across the 19.8 million acres planted. Yields Actual data on the performance of Bt corn lends partial support to the first conclusion regarding increased yields. In certain circumstances, Bt corn does appear to increase yields, at least in most fields. But even in such fields, there are alternative technologies that can deliver comparable control at the same or less cost. In addition, there are proven methods to prevent ECB populations from reaching damaging levels in the first place. Insecticide Use Data are presented which clearly refute the EPA s conclusion that Bt corn has reduced insecticide use. The percent of acres treated for management of the ECB has increased since the introduction of Bt corn despite very low ECB population levels in 1998 and The EPA depends on a serious error and a questionable set of assumptions in reaching the opposite conclusion. At a minimum, EPA must correct its mistakes and issue a revised set of estimates of the impact of Bt corn on ECB insecticide use. Economic Impacts Data on the performance of Bt corn, and several independent economic assessments, provides strong support for four conclusions 1

2 Under the most optimistic assumptions, increased yields from Bt corn in 1997, a year of high ECB pressure, may have covered near across-the-board losses in 1998 and The benefits of Bt corn are likely in decline as a result of the emergence of resistance and adverse impacts on nontarget beneficial insects. Bt corn technology has been the most expensive ever introduced in major corn hybrids and has delivered limited benefits; it will almost certainly not sustain the long-term upward trend in corn yields achieved since the 1940s The added costs of compliance with refugia requirements and resistance management plans, field monitoring and regulatory reviews, market segregation, and impacts on export demand exceed the onfarm benefits associated with the technology. EPA s Benefit Assessment The EPA states that the principle expected benefit from Bt corn was increased yields. The agency asserts that this benefit has been realized, and further states that the percent of acres treated with insecticides for control of the European corn borer have fallen from 8 percent of national corn acres planted prior to the introduction of Bt corn hybrids to 5 percent in EPA assesses trends in insecticide use for ECB management in four states with, on average, 33 percent of corn acres planted to Bt corn in 1999 (Iowa, Illinois, Nebraska, Missouri), compared to two states with just 10 percent of corn acres planted to Bt-hybrids (Indiana and Wisconsin). EPA then tests the hypothesis that corn insecticide use targeting the ECB declined more significantly in the four high-adoption states compared to the two low-adoption states. In the high adoption states, EPA concludes that the percent of acres treated for ECB control fell by about one-third, from 6 million acres treated to 4 million. Furthermore, as expected for low percent adopter states, neither the ECB pesticides or total insecticides show a reduction in acre treatments. (EPA benefits assessment, page IIE5). EPA notes that 1998 and 1999 were years marked by low ECB pressure, perhaps explaining part of the decline in national acres treated. EPA s Assumptions While few details are offered on how the agency reached these conclusions, it is clear that in some key respects, flawed assumptions and incorrect information were utilized. EPA states that just four insecticides are recommended for use in ECB control chlorpyrifos, permethrin, methyl parathion, and lamba-cyhalotrin (see page IIE5) and appears to base its assessment of ECB insecticide use solely on trends in the percent of acres treated with these insecticides. This is incorrect; several other insecticides are registered and recommended for use in managing the ECB. The acreage treated with 2

3 other products is currently not significant, but it has been in the past and may become so again in the future. The agency s reported decrease in ECB insecticide use is based on decreased use of these four active ingredients. According to EPA, Most of the reduction is with Chlorpyrifos and Methyl parathion. Prior to introduction of Bt corn, these two insecticides accounted for 10 percent of acres treated. Use fell to 6 percent of acres treated in 1999 a drop of 4 percentage points. EPA s conclusion that ECB insecticide use has fallen about one-third rests heavily on how the agency divides the acreage treated with chlorpyrifos and methyl parathion between treatments for corn rootworms versus treatments for ECBs. The agency s assessment does not directly discuss this critical assumption, but the split used in the agency s projections can be inferred from the data presented. In the table on page IIE5 of EPA s benefits assessment, the agency presents data on the percent acres treated over time with the four active ingredients recommended for ECB control. Nowhere does the agency acknowledge that two of these four insecticides are also recommended, and typically applied to control soil borne insects, principally the corn rootworm. Prior to the introduction of Bt corn (average for 1992 to 1995), the agency reports that 13 percent of national corn acres were treated with the four ECB-recommended insecticides Chlorpyrifos, 8 percent of national acres treated. Methyl parathion, 2 percent. Permethrin, 3 percent. Lambda-cyhalothrin, 0 percent. These data and the 13 percent total acres treated -- cover both ECB and rootworm applications. The insecticide-specific figures match those reported by the USDA s National Agricultural Statistics Service from its annual field crop chemical use surveys. It is appropriate that these surveys are the primary source of corn insecticide use data in the EPA s assessment. Elsewhere, the agency states that prior to the introduction of Bt corn, 8 percent of national corn acres were treated with the four recommended insecticides for ECB control. There is widespread agreement that the 3 percent of acres treated with permethrin targeted the ECB. Accordingly, the agency must have attributed one-half of the 10 percent of acres treated with chlorpyrifos and methyl parathion to ECB control and the other half to corn rootworm treatments. The sum of 3 percent acres treated with permethrin plus one-half the acres treated with chlorpyrifos and methyl parathion yields EPA s estimate of 8 percent national corn acres treated for the ECB prior to the introduction of Bt corn. 3

4 In addition, the reported 3 percent decline in acres treated from the pre-bt corn era to 1999 equals the sum of the 1 percent decline in permethrin acres treated plus one-half the decline in chlorpyrifos plus methyl parathion acres treated. EPA Errs in Major Assumption EPA s assumed split in chlorpyrifos plus methyl parathion acres treated for ECB and corn rootworm is incorrect, however, and a major flaw in EPA s analysis. Chlorpryifos accounts for over half the acres treated with four Rootworm + ECB products. In its recently completed Registration Eligibility Document (RED) for chlorpyrifos, EPA reports the results of detailed assessments of chlorpyrifos use and dietary, ecological, and worker-safety risks. In the Use Characterization section of the June 2000 revision of the Fate and Environmental Risk Assessment Chapter of the chlorpyrifos RED, the EPA states that The largest crop use of chlorpyrifos is a pre-plant or at-plant soil application with soil incorporation (page 4). In the section discussing corn uses of chlorpyrifos, the EPA states that Chlorpyrifos is primarily applied to corn as a granular formulation (i.e Lorsban 15G) and liquid formulation (i.e., Lorsban 4EC). (page 113). These pre-plant or at-plant applications are all for control of soil borne insects, as any farmer and entomologist active in the Midwest knows. According to the USDAsponsored Crop Profile for Corn (Field) in Iowa, corn rootworms are the most significant insect pest problem in the U.S. Midwest from the standpoint of insecticide use. Soil-applied insecticide treatment is generally a standard practice in corn acreage following corn The National Center for Food and Agricultural Policy (NCFAP) released a September 1997 paper entitled The Use of Organophosphate (OP) and Carbamate Insecticides in U.S. Crop Production. The author, Leonard Gianessi, reports that Corn rootworm larvae are the primary and most damaging insects in corn production. Chlorpyrifos is used most frequently in the Corn Belt because of its efficacy against both cutworms and rootworms. In 1998, the NCFAP released an extensive database on OP insecticide use and alternatives developed under a contract with the EPA. In characterizing chlorpyrifos use 4

5 on corn, the NCFAP assessment draws upon information provided by the major manufacturer of chlorpyrifos, Dow AgroSciences. In the section on Application Methods/Timing, the report states Majority of use (7,100,000 lbs ai) is at plant T-banded applications of Lorsban 15G to continuous corn in the Midwest for control of corn rootworm larvae. Use of this product also provides benefit of protection from cutworms. Foliar applications of Lorsban 15G (aerial and ground) targeted against the European corn borer represent approximately 2% of the total volume or 150,000 lbs ai. The State of Iowa carried out a survey of pesticide use in Iowa crop production in 1995 (results are accessible on the Internet at Just over 31 percent of the state s corn acres were treated with an insecticide in Over 60 percent of corn following corn was treated for corn rootworms and an additional 14.5 percent for black cutworms, another soil borne insect. Just 5.6 percent of corn rotated with soybeans was treated with an insecticide 5.3 percent for rootworms and another 2.3 percent for cutworms. Of the 31.3 percent of Iowa corn acres treated in 1995, the corn rootworm was the principle target pest of 22 percent and cutworms triggered another 6.1 percent of acres treated. ECB control lead to only 2.6 percent of acres treated (data from Table 7). Two products accounted for these 2.6 percent of acres treated permethrin (2.3 percent) and foliar Bt sprays (0.4 percent). University of Illinois corn IPM specialist Dr. Mike Gray projects that the great majority of corn acres treated with chlorpyrifos are targeted at corn rootworms (personal communication with Charles Benbrook, October 12, 2000). The Iowa survey, basic corn pest management texts and reference books, and university experts agree that the same conclusion applies to acres treated with methyl parathion the majority target soil borne insects, not the ECB. Hence, the EPA clearly erred in assuming that half the acreage treated with chlorpyrifos and methyl parathion has targeted the ECB. Alternative Assumptions and Projections The agency s approach to assessing the impacts of Bt corn on insecticide use is sound but its assumptions must be revisited. Obviously, the key step is determining why farmers have applied different products that are registered for use on a range of insects, including the ECB. In estimating total ECB insecticide use, Table 1 assumes that one-quarter of the acres treated with Rootworm + ECB products targeted the ECB, the other threequarters were applied largely to control corn rootworms and other soil-borne insects. The assumption of a 25%-75% split probably overstates the portion of chlorpyrifos and 5

6 methyl parathion acre treatments targeting the ECB, but also likely understates the portion of bifenthrin acres treated targeting the ECB. Across this category of products though, a 25%-75% split is surely closer to the truth than EPA s 50%-50% split. In Table 1 (all tables appears at end of the paper), the national percent of corn acres treated are presented for insecticides grouped into three categories. These include products used primarily for: ECB control, Control of soil borne insects, especially the corn rootworm complex, or Products applied to manage both pests (labeled Rootworm + ECB products in the tables that follow. As shown in the Table 1, there were four insecticides used primarily for ECB control in 1999, six predominantly for rootworm control 1, and four active ingredients that are applied to manage one or the other, or both pests. Most farmers apply these products at planting for rootworm and soil borne insect control; relatively few apply them later in the season for ECB control. A very few farmers apply them twice in managing both soilborne insects and ECBs. Data in Table 1 provide an historical perspective back to 1971 on national corn insecticide use targeted to the management of the ECB and corn rootworm complex. Data are from USDA surveys. The total percent of acres treated with ECB-only, rootworm-only and Rootworm + ECB products are presented in the table for 1971, 1982, 1995, 1996, 1997, 1998, and Total national corn acres treated with insecticides to manage the ECB by year in Table 1 are the sum of acres treated with ECB-only insecticides and one-quarter of the total percent of acres treated with Rootworm + ECB products. Nationwide, based on the more realistic 25%-75% split, the percent of corn acres treated for ECB rose from 6.75 percent in 1995 prior to the introduction of Bt corn to 8.5 percent in 1999, an increase of 26 percent. This finding contrasts sharply with EPA s conclusion that the percent of acres treated for ECB control fell from 8 percent of acres treated in 1995 to 5 percent in 1999 about a 37 percent drop. Recall as well that both 1998 and 1999 were very low ECB pressure years. Following the high-levels of ECBs in 1997, it is understandable that many growers 1 The corn insecticide Aztec contains two active ingredients tebupirimiphos and cyfluthrin. The USDA s National Agricultural Statistics Service reports the percent of acres treated with this insecticide according to its two active ingredients. For example, in 1999, two percent of national corn acres were treated with Aztec, which were reported as two percent acres treated with tebupirimiphos and two percent acres treated with cyfluthrin. According to University of Illinois corn IPM specialist Dr. Michael Gray, Aztec is used predominantly for rootworm control (personal communication with Charles Benbrook, October 12, 2000). 6

7 expected 1998 to be another year with relatively high ECB pressure. This did not prove the case. Throughout the summer and fall of 1998 reports circulated in the Midwest of low populations of ECBs and the need to scout fields to help estimate likely population levels in crop season 1999 key information growers need to determine whether the added investment in Bt corn varieties might payoff. Surely when farmers were buying seed for the 1999 season, many must have been more aware of ECB levels in their fields than in previous years. Many university-based corn IPM specialists issued statements to the grower community urging them to scout ECB levels in the fall. In late 1998 articles began circulating in the farm press describing either modest or no economic return to the added investment in Bt corn. Still, acreage planted rose sharply in 1999 to over 19 million acres. During the 1999 crop season, three factors working together should have markedly reduced ECD insecticide treatments. There was the widely discussed downward trend in ECB pressure, the big increase in acres planted to Bt corn in 1999 compared to 1998, and rock-bottom and declining corn prices. Still, insecticide use targeting the ECB went up in Why the Increase in ECB Insecticide Use? Based on discussions with several entomologists in the Midwest, grower surveys, and review of the literature, two factors stand out as most plausible in triggering the increase in ECB insecticide use. First, the emergence of Bt corn has undoubtedly heightened knowledge of and attention to ECB pressure and yield losses. Thousands of comparative field trials were conducted in the period that proved the efficacy of the technology in the presence of high ECB pressure. The untreated check plots were typically planted to otherwise identical conventional corn varieties and documented the degree of ECBrelated yield loss farmers were suffering in high-pressure years. Since these trials were intended to test the performance of Bt-hybrids in the presence of ECBs, trial locations and experimental designs sought to assure the new varieties were truly put to the test. Understandably, the trials did not address the frequency of high-ecb populations or the economic performance of Bt-hybrids over many years in the face of variable ECB pressure. For years most corn farmers have accepted periodic ECB yield losses as part of the ups and downs of farming. This attitude persisted in part because of the lack of a cost-effective chemical treatment in managing the ECB in typical farming systems across most of the Cornbelt. But as farmers read more about the hidden cost of living with the ECB, some no doubt decided to spray for the insect rather than plant Bt-transgenic hybrids. A second set of reasons why ECB insecticide use has risen may stem from shifts in the composition of nontarget and/or beneficial species in Bt cornfields as a result of exposure to the Bt-toxin in plant tissues. Since several key generalist predators depend 7

8 on ECBs as a primary food source during parts of the season, the relative absence of ECBs in Bt cornfields may be reducing predator populations, at least during certain parts of the year. It may also progressively depress beneficial insect population levels and shorten food chains from year to year. It remains unknown the extent and consequences of these shifts. Plus, such changes are only beginning to emerge, since this is such a new technology. Reduced populations of generalist predators, however, will tend to allow other insect pests to thrive, perhaps triggering the need for additional insecticide applications. Other longer-run onfarm ecological impacts of Bt corn use must be more carefully monitored and studied to sharpen future benefits assessments. Impacts of Bt-toxins on soil organisms might affect the rates of organic matter turnover, or favor damaging root pathogens or nematode species. Unintended adverse consequences could arise in a vast array of different ways as a function of combinations of soil type, farming systems, tillage, weather, chemical use, and pest levels. While hard to predict and often hard to detect, unintended consequences are likely. Technology-induced ecological changes can, in turn, trigger the need for other changes in pest management systems and sometimes actually lead to increases in pesticide use above the levels common prior to the technology s introduction. This near-universal law of pest management is playing itself out now with all first-generation GMO-plant varieties, including those engineered to express Bt toxins and herbicide tolerant varieties. In the absence of a shift toward more balanced, multitactic corn IPM systems, the emergence of partially resistant ECB populations and shifts in insect pest complexes will likely result in a gradual upward trend in insecticide use in corn production despite the planting of Bt-hybrids. Increased Yields in Perspective In its economic analysis, EPA reports that the added cost of Bt corn hybrids is likely to pay off only in years with moderate to high ECB infestation levels. Entomologists in several states reported that a lack of pressure in 1998 and 1999 resulted in virtually no difference in yields planted to Bt-hybrids in contrast to otherwise similar hybrids. For example, University of Missouri extension agronomists found no differences in yields across 15 sites in Missouri as a result of generally low infestations ( In artificially infested trials, they determined that the economic threshold was one ECB larvae per plant, causing at least a 4.2 bushel reduction in per acre yields. The simple version of a Purdue University economic assessment was based on historical data that show ECB infestation levels in Indiana will reach one ECB per plant one in every four years and reduce yields about 6.5 percent, assuming no other control 8

9 tactics are used. 2 Based on an expected yield of 150 bushels, a price of $2.50 per bushel, and the assumption Bt corn is 100 percent effective, the Purdue team projects that farmers should be willing to pay $6.10 extra per acre to plant Bt corn ($24.37 loss avoided, divided by four years). This is, of course, below the added cost of Bt seed, and helps explain why Indiana is among the low-adoption states. A more complicated analysis is also carried out taking into account many other variables impacts on planting dates, probabilities of economic infestations, yield losses, corn prices, adherence to resistance management plans, and efficacy. Taking all these factors into account, the Purdue researchers project benefits between $4.50 and $5.00 per acre for two common Bt corn varieties well less than the premium of $8.00 to $12.00 per acre for the seed. University of Illinois extension entomologists Dr. Kevin Steffey and Dr. Michael Gray wrote a November, 1999 article entitled To Bt or Not to Bt in 2000 ( It alerts growers that infestation levels have been low through most growing areas in 1998 and 1999, and that few growers planting Bt-hybrids in either year had received an economic return to their investment. The message was clear -- in the absence of some tangible evidence that ECB populations would increase on a given field in the year 2000 season, growers should think long and hard about spending the extra money for Bt-hybrids. IPM experts in most Midwestern states made the same point in a myriad of ways. The message obviously got through -- the percent acres treated in year 2000 declined about one-quarter relative to crop year EPA Projects Net Bt-Corn Benefits of $65.4 million Based on the widely accepted assumption that Bt corn costs $10.00 per acre more than conventional hybrids, the EPA presents a matrix with the return per acre at two corn prices ($2.50 and $3.50 per bushel), three yield levels, and five levels of ECB infestation. The $3.50 per bushel market price is $1.50 or more above cash prices throughout the period, and hence the returns at that price level have little bearing on adoption rates in recent years. The $2.50 per bushel price is close to the realized cash price farmers have received when all government payments are taken into account. In 1998 and 1999, Sparks Commodities projected the full realized corn price at $2.58 and $2.65 per bushel, and projected a price of $2.53 for 2000 (see page 8, Farm Journal, October 2000). These prices were close to the projections of many market analysts and widely reported in the farm press. At the lowest infestation level analyzed, 0.5 ECB per corn plant, the returns to Bt corn are negative on farms harvesting 125 and 150 bushels per acre. Only very high 2 The Economics of BT Corn: Adoption Implications, by Jeffrey Hyde, Marshall Martin, Paul Preckel, and Richard Edwards. Purdue University Cooperative Extension, Accessible at 9

10 yield farms harvesting 175 bushels per acre would earn a modest return less than one dollar per acre above the added costs of Bt corn hybrids. At one ECB per plant, the EPA-projected return rises to $5.63 at 125 bushels close to national average yield, which was bushels in 1999, according to USDA/NASS data. Returns reach $11.88 at 175 bushels assuming corn sells for $2.50 per bushel. After accounting for the costs of resistance management plans, heightened focus on pest management, and other factors, the EPA projects an average net benefit per acre of $3.31 on the 19.8 million acres of corn planted to Bt-hybrids in 1999, resulting in a total net benefit estimate of $65.4 million. Other analysts have reached different conclusions regarding net benefits, as noted above. While the actual benefits have and will continue to vary from year to year, it is important to place them in perspective relative to the historic return farmers have received from an added $1.00 expenditure on advanced corn genetics. Lower Return on Expenditures Recall that corn producers spend about $10.00 per acre more to plant Bt-hybrids. Thus, across the nation, farmers spent some $198 million dollars more on seed that returned net benefits of just $65.4 million, based on EPA s analysis. So, farmers spent $198 million and got $263.4 million in return ($198 million extra spent on seed plus the estimated net benefits of $65.4 million), or a $1.33 return on expenditure of a $1.00. Traditionally, agricultural inputs have returned $2.00 and often $4.00 or more per $1.00 invested. This was certainly the case with hybrid seed corn from the 1970s through the mid-1990s when genetically engineered corn reached the market, as evident in the Table 2. From 1975 through 1997, farmers received about $2.30 per added dollar spent on corn seed. From the mid-1980s through 1994, the return averaged over $5.00 per $1.00 invested as a result of impressive yields gains -- over 1.5 bushels per year -- and slower increases in the price of seed. At Best, Very Modest Benefits The key point is that even under optimistic assumptions, Bt corn has delivered modest benefits to farmers and the nation. The estimated $1.33 return to expenditures on Bt corn is less than half the return earned by farmers investing in other corn genetic improvements over the last three decades. The relevance of this finding to EPA s regulatory decisions evolves from the basic riskbenefit balancing standard set forth in federal pesticide law. In the face of relatively modest benefits, relatively modest risks should tip the risk-benefit scales against Bt corn engineered to avoid ECB damage. Risk of Resistance and Nontarget Impacts Undermine Even Modest Benefits The scales are further tipped by the likelihood of the emergence of resistance in ECB populations and worsening problems with secondary insect pests as a result of the impact of Bt corn on generalist predators and biological control processes. Evidence is mounting 10

11 that Bt corn has, or probably will over time exacerbate other insect problems. For these reasons, EPA must discount over time the modest benefits associated with this technology. This finding of at best modest net benefits that are also likely to be short-lived is also relevant to the broader questions surrounding Bt-transgenics. Bringing Bt corn to market has been, without doubt, the most expensive genetic technology ever introduced into corn production. In light of these enormous costs, it is appropriate to question whether the efforts of breeders and molecular biologists, regulators, agronomists, entomologists and other specialists in both the public and private sectors might have accomplished more if targeted toward other more universal corn yield constraints. ECB Management Options are Available The ECB is an episodic pest. Damaging population levels are triggered by a combination of factors including the weather, cropping history, timing of planting and harvest, tillage and pest management systems, and past control tactics. Given that the pest reaches damaging levels in just a few years out of 10 in most regions, it is clear that most farmers are effectively managing it under most conditions. It is equally clear that further steps can be taken to suppress populations further and limit even more the area infested at levels triggering the need for control actions whether spraying an insecticide or planting Bt corn. Many farmers utilizing sustainable farming systems report little or no trouble with ECBs in any year. The basic components of such systems, and their success in suppressing the ECB and rootworms, are documented in one of the case studies in the 1989 National Academy of Sciences report Alternative Agriculture (see Case Study 1). The Spray Brothers farm is a diversified livestock-row crop farm in central Ohio. It has been producing high yields of corn and soybeans, forages and small grains without any pesticides for over 20 years. The farm has also cooperated with a number of researchers at Ohio State University interested in exploring the biological and ecological factors contributing to the farm s success. Research by Dr. Larry Phelan, an OSU agronomist, has focused in recent years on the role of corn plant nutrition in explaining the lack of ECB pressure and damage on the Spray farm, while fields just across fencerows have experienced periodic damage and yield losses much like other Midwestern corn farms. Phelan is convinced that the critical difference between the sustainable system on the Spray Brothers farm and otherwise similar conventional farms is related to nutrient and mineral fluxes and availability, and the role of nitrogen uptake in meeting secondary plant nutritional needs. On conventional farms where plants receive intensive flushes of readily available nitrogen, corn plant tissues grow rapidly but appear to not contain adequate levels or diversity in secondary nutrients and minerals to fully support defense mechanisms against the ECB. Nitrogen uptake on the Spray Brothers farm is more gradual. Root systems develop more fully and become more efficient in extracting available nitrogen from the soil profile. As a result, the plants also benefit from the extraction of higher levels of secondary nutrients and minerals, which enter the plant in a ratio relative to nitrogen that 11

12 is closer to optimal in supporting the plant s full array of ECB defense mechanisms. Phelan has documented fields where there have been comparable numbers of adult beetles collected from corn plant tissues, but much more modest feeding damage. Through as yet undiscovered mechanisms, corn plants appear to be emitting some chemical signal that either repeals or discourages ECB feeding or attracts predators of the ECB. Nutrient management and general plant health is surely a key factor in managing ECB losses, since it is also widely acknowledged that ECB losses tend to be more serious in fields subject to drought stress. In addition, there are several other known management strategies to suppress the ECB. The planting of shorter season varieties as early as possible can often lead to harvest before damaging levels of second or third generation ECBs emerge. Much can be done post-harvest to reduce over wintering populations including the chopping of stalks, certain tillage practices, and the planting of cover crops to encourage diversification of insects feeding in corn stubble and trash. Crop rotation is a proven control measure. A number of research teams are pursuing promising area-wide management tactics designed to gradually suppress populations across a wide area, in this way limiting the chances that damaging levels will re-emerge, even under conditions favorable to the insect. Last, seed companies continue to make progress in the breeding of conventional hybrids with higher levels of resistance to the ECB. B. Bt-Sweet Corn Remains a Largely Untested Technology The EPA s benefit assessment of Bt sweet corn is based largely on field trial data submitted by the manufacturer, Novartis. Commercial plantings of Bt sweet corn, especially for the fresh market, have been very limited and hence there is inadequate data to fully evaluate benefits. EPA is correct in assessing separately the benefits of Bt sweet corn grown for the fresh market in contrast to sweet corn destined for food processing. Fresh market sweet corn is subject to more rigorous grading and cosmetic standards than processing sweet corn. A significant number of today s insecticide applications on fresh market sweet corn are required to avoid any visible worm damage, even on the very tips of sweet corn cobs. Corn destined for processing, however, can be sorted and trimmed, allowing somewhat higher levels of infestation. Even small differences in acceptable worm thresholds can translate into a major difference in insecticide sprays. Insecticide usage on processing sweet corn is far less intensive than on fresh market corn. Most acres destined for processing are treated no more than twice with insecticides. Synthetic pyrethroids account for the vast majority of acres treated. The major two active ingredients applied permethrin and lambda-cyhalothrin are applied at low rates and pose limited risks to farm-workers and virtually no risk to consumers, since residues rarely if ever appear in processed sweet corn products. Through its 12

13 Pesticide Data Program, the USDA tested processed sweet corn in 1994 and 1995 and found no residues of these insecticides. Indeed, processed sweet corn was virtually pesticide free. Fresh market corn, on the other hand, is intensively sprayed, as documented in the EPA s benefit assessment and USDA pesticide use data. The organophosphate methomyl is the most heavily used product and was applied in 1998 on 48 percent of the acres planted for the fresh market, and an average of 6.6 applications were made. In Florida, 79 percent of the acres were treated in 1998 with methomyl an average of 8.6 times. Most acres also received two to three applications of a synthetic pyrethroid. Need to Focus on Fresh Market Benefits Florida leads the nation in the production of fresh market sweet corn. To date, commercial plantings of Bt sweet corn have been very limited according to Madeline Mellinger, President of Glades Crop Care (GCC) in Jupiter, Florida. 3 According to Mellinger, a significant portion of Florida s sweet corn is exported to Great Britain and other European countries (personal communication with Charles Benbrook October 17, 2000). Last year, several grower-shippers were contacted by their European buyers and asked not to offer for sale any GMO sweet corn varieties. Glades Crop Care is aware of a few small field trials this season with Bt sweet corn, as well as very limited commercial plantings. In recent years the pest complex facing sweet corn growers has shifted from largely fall armyworms and other Lepidopteran species to a broader mix of insects. Silk flies have become a particular problem and trigger about half the insecticide applications now made in producing fresh market sweet corn in Florida, according to Mellinger. Bt sweet corn will have no impact on this significant and growing portion of today s sweet corn insecticide applications. Most Florida sweet corn fields are sprayed a dozen times per season and some require 20 or more sprays. In EPA s assessment, the agency reports that the average fresh market sweet corn field in Florida was sprayed 17 times with insecticides in In the case of Lepidopteran sweet corn control in Florida, the proliferation of new insecticides from the early 1980s through today has given growers the tools to keep this family of insects under damage thresholds in most years, albeit at considerable cost in insecticides. Bt sweet corn might prove effective in suppressing some Lepidopteran species, at least for a few years, but can be expected to also trigger significant shifts in populations of both current and secondary pests and related beneficials. These ecological phenomena need to be taken into account in evaluating the sustainability of benefits associated with all Bt crops, as well as in projecting the impact of Bt crops on insecticide use and reliance over time. 3 For years GCC has scouted and provided IPM services to many of Florida s leading fresh market sweet corn growers. 13

14 C. Benefits of Bt Cotton Insect pest management in cotton has historically triggered the need for extremely intensive use of insecticides. Resistance has been a recurrent problem, forcing farmers to switch from one family of chemistry to another. The causes and mechanisms of resistance are well known in the case of most major cotton insects. Indeed, cotton insect pest management has been among the most fully researched components of any agricultural system. Lessons learned from many false starts and short-lived breakthroughs must provide the context for the evaluation of the benefits of Bt cotton. The EPA s current benefits assessment does not adequately draw upon these lessons in tempering its rosy, but cursory assessment of Bt cotton benefits. Nearly all new cotton insect pest management technologies, and innumerable insecticides, have worked well in the early years following introduction. The long growing season in cotton production areas are among the conditions that favor genetic adaptation in insect populations. In general, the faster and more fully farmers have embraced new chemical-based insect control technology, the shorter its expected lifespan. Accordingly, assessment of the benefits of Bt cotton, which is merely a biological delivery mechanism for a chemical-based management solution, must encompass not just the early years when the technology works reasonably well under most conditions. It should project the likely time frame for the emergence of resistance and the likely changes in pest and beneficial insect complexes in the interim. A key question should be confronted after Bt cotton is no longer cost-effective, will the insect management challenges facing farmers be different in any significant way? Impacts on Insecticide Use Cotton is plagued by a number of major insects. Control measures are continuously shaping the interaction between current pests, potential pests and beneficials. Accordingly, it is complicated to accurately predict the impact of any new technology on cotton insects. Even with solid data and clear-cut results, researchers know that pest complexes and pressure can change quickly. For this reason, a thorough benefits assessment of Bt cotton will require a much broader appraisal of impacts on production systems and species interactions in the field. Changes in the number of insecticide treatments is not the only relevant performance parameter and could lead to premature confidence that Bt cotton will contribute to a sustainable solution to cotton farmers historic problem managing Lepidopteran pests. The EPA benefits assessment draws upon the USDA Pesticide Impact and Assessment Program in projecting reductions in insecticide use in several states. In high adoption states, EPA concludes that Bt cotton has reduced insecticide acre-treatments 14

15 targeting the bollworm-budworm complex (BBW) of insects by about one-half, from 3 applications per acre to 1.5 on average. EPA also notes a slight increase in the use of other insecticides, presumably needed to control, secondary pests previously controlled by the OPs and synthetic pyrethroids spayed to manage the BBW complex. Overall, EPA projects that Bt cotton has cut insecticide sprays by 1.2 applications per acre on average in high adoption states. The 1.2 sprays per acre translates, according to EPA, into about 7.5 million acretreatments in 1999, or 0.6 acre treatments when applied across the 13.3 million acres planted in Grower economic benefits are projected to be $12.80 per acre in 1999 after taking into account the higher cost of seed. As the case with the EPA s assessment of Bt corn benefits, few details are presented regarding the key assumptions in the agency s model. It is clear, however, that the model fails to encompass many of the dynamic factors affecting the benefits of any cotton insect pest management technology or system. Regardless of the degree to which the agency s estimates reflect reality in crop year 1999, there are many reasons to project circumstances will change. Insecticide Use Patterns The best way to gain perspective on changes in insecticide use patterns is to look at state-level data in high adoption versus low adoption states. Over three-dozen insecticides have been applied on cotton farms over the last two decades. Close to half either solely or partially target the budworm-bollworm (BBW) complex of insects that are also the target of Bt cotton. For the purpose of assessing the impacts of Bt cotton, cotton insecticides can be classified into the following groups Those targeting the BBW complex the pink bollworm, tobacco budworm and boll weevil. Whitefly/Thrips insecticides, and products targeting other sucking insects. Multiple target insecticides that are used to suppress populations of several pests, or which are used as a synergist with established synthetic pyrethroid or OP insecticides targeting either the BBW or whitefly/thrips complexes. Other insecticides targeting true bugs such as stink bugs, mites, and other species of insects. It is important to acknowledge that because of the diversity of cotton insect challenges and IPM systems, there are no doubt exceptions around the country to the classifications used in this analysis. In addition, several cotton insecticides are very broad spectrum and can target a wide array of insects at varying life stages. Even within a given state, an active ingredient like acephate or chlorpyrifos might be used in a halfdozen different ways targeting an equal number of pests. According, the data presented below should be considered a rough snapshot of insecticide use by class. More detailed state level data, and the help of regional cotton IPM experts will be required to fine-tune the classifications, and hence the conclusions reached. 15

16 Table 3 presents an overview of the intensity of use of these classes of insecticides in cotton production at the national level from 1992 through The table reports average acre-treatments per planted acre by active ingredient, and then totals across all the active ingredients in a given group. This key indicator of the intensity of use is the percent acres treated multiplied by the number of applications. Hence, it measures the average number of times an acre was likely to be treated with a given pesticide; the higher the percent acres treated, the higher the number, the greater the number of applications, the higher the average number of acre-treatments per planted acre. For example, acephate was applied to 14 percent of national cotton acres in 1999 an average of 1.5 times. Hence, the average acre planted to cotton received 0.21 acretreatments with acephate (0.14 share of acres treated times 1.5 applications per acre). Malathion was the most intensively used insecticide: 40 percent of acres were treated an average of 6.8 times, or about 2.7 times per acre across all planted acres. The trend in acre-treatments per acre for the BBW complex is clearly down from a peak of over 3 in 1995 prior to the introduction of Bt cotton to 0.85 in Clearly changes in pest pressure and IPM systems have played a significant role in this drop, as has the introduction of Bt cotton, at least in some states. The biggest reductions have occurred in the use of methyl parathion, profenofos, and thiodicarb. The former two very hot OPs have triggered resistance problems and regulatory restrictions; most of the reduction in their use had occurred in 1996, right after heavy use in crop year 1995, a year with heavy BBW pressure. Hence, these reductions have little if anything to do with the introduction of Bt cotton. Table 3 also shows that the use of other categories of insecticides has either stayed about the same or risen modestly, with the exception of malathion use. The big jump in malathion use in 1999 largely reflects heavy use in regional boll weevil eradication programs. State-level data are inconsistent. In some high adoption states, especially Arizona (see Table 4), BBW applications have fallen dramatically, with much of the decline likely attributable to Bt cotton. In Alabama, another high adoption state, BBW insecticide applications more than doubled from 1997 to 1999, despite a large increase in acres planted to Bt cotton (see Table 5; USDA use data are not available in earlier years). Mississippi cotton growers reduced BBW insecticide acre-treatments from over 9 in 1995 to just over 1.5 in 1999, although there was a sizable (5.8 acre-treatments per acre) increase in the Multiple Pest/Synergist category of products (see Table 6). Most of the BBW complex decline, however, cannot be attributed to Bt cotton, since BBW applications dropped from 9.4 in 1995 to 3.6 in 1996, the first year of limited commercial plantings. Accordingly, it appears Bt cotton might have cut BBW insecticide use about 1.5 acre-treatments per acre about the same as EPA s estimate of reductions in national BBW insecticide use. 16

17 But some low-adoption states have also markedly reduced BBW acre-treatments. Texas cotton, for example, was treated an average 1.3 times with BBW insecticides in 1995, up from 1 application in 1994 and 0.7 in Despite just 7 percent of acres planted to Bt cotton in 1999, BBW insecticide treatments fell to 0.5. Clearly, shifts in pest pressure and other factors impacting cotton IPM systems have been driving BBW insecticide use just as much, and in many states more so than the introduction of Bt cotton. Reductions in Arizona in Perspective Researchers at the University of Arizona have compiled and made available on the Internet extensive data on cotton pesticide use and pest infestations (go to Cotton insect pest loss data by year, pest, applications, and cost per ace are reported from 1979 through Data for 1999 are reported separately for Bt cotton and conventional varieties to allow comparison; the following analysis draws on these data. In 1999 lygus bugs were the most expensive insect plaguing Bt cotton growers in Arizona; a total of $22.47 per acre was spent on average in managing this insect. These control costs accounted for 65 percent of total insect control costs. Even so, lygus bugs still caused an estimated 3.8 percent yield loss, far more than all other insects combined. Whiteflies accounted for another 32 percent of total control costs, or $11.10 per acre. These insects caused only 0.18 percent yield loss. Across all insects, there were 1.59 applications of insecticides costing $34.49 per acre on Bt cotton acres. In conventional cotton the same year, there were 2.5 insecticide applications per acre costing $ Lygus bugs remained the most costly insect, triggering $15.35 in insecticide applications and reducing yields 2.4 percent. Pink bollworms were the second most costly insect, accounting for $10.80 in control costs per acre and a 2.5 percent yield loss. It is also worth noting that Bt cotton growers spent, on average, $3.25 on a soil insecticide at planting in 1999 whereas conventional cotton growers were able to bypass this application. These data raise several questions Given that Bt cotton has decreased BBW applications so dramatically from 1995 through 1999, why the modest difference in insecticide applications on Bt cotton acres in contrast to conventional acres in 1999? Why was the lygus bug easier and less expensive to control in conventional cotton in 1999, compared to Bt cotton? Arizona cotton IPM expert Peter Ellsworth points to two factors explaining, at least in part, trends observed in Arizona insecticide use. First, adoption of the IGRs pyriproxyfen and buprofezin has made a major difference across the cotton insect pest spectrum. These reduced risk insecticides have made a big difference in managing the 17

18 whitefly/thrips complex of insects, especially early in the season. Applications have made it possible for growers to delay or avoid use of disruptive, broad-spectrum materials. This has created a window during which populations of beneficials have expanded in step with species in the BBW complex. According to Ellsworth, some of the reduction in insecticide use attributed to Bt cotton has probably been made possible by the improved, softer management of the whitefly/thrips category of insects. He points to a second encouraging development -- an unmistakable area-wide insect pest suppression effect from the planting of Bt cotton in Arizona. Pest infestation and damage data collected over several years provides Ellsworth and Arizona colleagues a unique resource in assessing the impacts of new pest management technologies. He believes that even on farms not planting Bt cotton, growers are benefiting from an areawide suppression of the BBW complex, especially pink bollworms, from Bt cotton. In addition, he thinks that the IGRs are helping to suppress early season whiteflies enough to bring about a similar area-wide impact. He also notes that growers producing other crops are also doing a far better job with whitefly/thrip management, resulting in fewer insects moving from vegetable and fruit fields into cotton. Maximizing the Benefits of Bt Crop Varieties The dramatic changes in Arizona cotton insect pest management, and the complex dynamics driving these changes, show how difficult a thorough Bt benefits assessment will be, particularly when analysts strive to track and project changes over many years. The task becomes even more difficult if the full range of possibly viable alternative systems is included in the assessment. At the present time the cotton industry in Arizona is benefiting from two new insect management technologies Bt cotton and the newly registered IGRs. The former technology is likely to be plagued with the same problems with resistance and secondary pest problems if relied upon largely or exclusively for BBW control; the later technology has provided farmers a new method to diversify insect pest management systems, while also making it possible to avoid early season use of broad spectrum materials. The well-proven principles of biointensive IPM hold the key in structuring sustainable and affordable pest management systems, both in Arizona cotton and Illinois field corn. Such systems never rely too extensively on any one practice, tactic, chemical, or technology, and will exploit as many strategies for suppressing pest levels as possible. After just a few years of experience, it is clear that the net benefits of Bt crop varieties could be substantially enhanced, and sustained much longer, if the technologies were incorporated into biointensive IPM systems rather than looked to as a way to avoid the discipline inherent in more balanced, multitactic IPM systems. In future assessments of Bt crop benefits, the EPA needs to raise the bar by more fully considering pest management system-wide implications and ecological adaptations. The key questions must become -- Will the technology, as it is being utilized, reliably 18