Insect Resistant Field Corn (1)

Transcription

1 Plant Biotechnology: Current and Potential Impact For Improving Pest Management In U.S. Agriculture An Analysis of 40 Case Studies June 2002 Insect Resistant Field Corn (1) Leonard P. Gianessi Cressida S. Silvers Sujatha Sankula Janet E. Carpenter National Center for Food and Agricultural Policy 1616 P Street, NW Washington, DC Phone: (202) Fax: (202) ncfap@ncfap.org Website: Financial support for this study was provided by the Rockefeller Foundation, Monsanto, The Biotechnology Industry Organization, The Council for Biotechnology Information, Grocery Manufacturers of America, and CropLife America.

2 28. Field Corn (1) Insect Resistant Production Corn is the largest acreage crop grown in the US. Planted acreage totaled 80 million in 2000, which represents 25% of the acreage planted to all crops in the US [22]. Average corn yield in 1999 and 2000 totaled 134 and 137 bushels per acre, respectively. Corn for grain production was estimated at 10 billion bushels in 2000 with a total value of production of $19 billion, which represents approximately 28% of the value of all crops grown in the US [19]. The major use of corn produced in the US is as a livestock and poultry feed (6 billion bushels) while food, seed and industrial uses (including sweeteners, fuel alcohol and starch) account for 2 billion bushels. Exports account for 2 billion bushels [18]. All 48 coterminous states have corn acreage and, in many states, corn is the single most important crop in terms of acreage and production value. Corn production is centered in the Midwest, where ten states account for 85% of the US acreage and production. Individually the states of Illinois and Iowa account for more than 10 million acres of corn each. Table 28.1 contains estimates of field corn production and acreage for 36 major corn-producing states for These 36 states account for 99% of US corn acreage and production. The European Corn Borer The European corn borer (ECB) is an introduced insect species. It probably arrived in North America during the early 1900s in corn imported from Hungary and Italy for the manufacture of brooms. As full grown larvae, European corn borers spend the winter in corn stalks, corn cobs, weed stems or in a spun-silk covering located in plant debris [3]. Adult moths leave emergence sites in plant debris and fly to nearby areas of dense vegetation, primarily grasses in conservation lanes, along waterways or near fence rows. These locations are 2

3 referred to as action sites. The moths mate at night and the female leaves the action site to deposit eggs on the corn crop. Each mated female is capable of depositing an average of two egg masses per night for ten nights. Egg masses are small approximately ¼ inch in diameter and contain an average of 15 eggs. Larvae emerging from the egg masses move directly into the whorl for shelter and food. The larvae feed on the leaves, which result in small holes and patchy areas lacking leaf tissue. Eventually the larvae crawl out of the whorls and down the side of the stalk to burrow into the stalk of the corn plant, where they pupate during the summer. Moths that emerge in mid-summer fly to dense vegetation, primarily foxtail grass to feed, rest and mate. The mated females deposit eggs on recently tasseled corn plants. Each second generation female can lay about 400 eggs during her life. The majority of the second generation larvae feed on sheath and collar tissue or pollen. Some of the emerging second generation larvae will feed on other protected areas, such as under the husk in the developing ear [3]. The larvae go into diapause and spend the winter in plant residue. In northern corn growing regions (North Dakota, Minnesota, Wisconsin) the ECB goes through one generation per year; in much of the Midwest, Northeast and Mid-Atlantic states, two generations are typical; for the South (Alabama, Oklahoma, Tennessee, North Carolina, South Carolina), three generations are the norm and in the Southern growing regions (LA, MS, GA, AL), four generations are typical (Figure 28.1 shows areas of normal, high, medium and low ECB infestation in the US). For field corn, yield losses from ECB larvae are primarily physiological losses from reduced plant growth. Stalk tunneling results in shorter plants with fewer and smaller leaves. Movement of water and nutrients can be restricted over the entire kernel-filling period. During whorl stage of corn growth, there is between 5 and 6% loss in grain yield for each larva per plant. During the corn development stage, the loss per larva per plant is about 2 to 4% [3]. After three borers per plant, the relationship between numbers of borers and yield loss starts to level out. 3

4 In most cases the probability of a heavy attack by both generations is low. Since first generation moths prefer the most developed fields in an area and second generation moths generally target the least developed, many fields will escape significant damage by one generation or the other. Corn plants heavily infested by first generation borers are unattractive to egg-laying moths of the second generation. Infested corn plants produce an odor that is repellent to the moths. In addition, the excrement and frass of the first generation larvae repel the second generation moths [55]. European corn borer-damage results in poor ear development, broken stalks, and dropped ears. Most yield loss can be attributed to the impaired ability of plants to produce normal amounts of grain due to the physiological effect of larvae feeding on leaf and conductive tissue. With persistent autumn winds and dry weather, tunneling in the stalks can increase stalk breakage, resulting in substantial loss of ears during harvest. Newly hatched larvae can be blown off the leaves by winds, crushed by moving plant parts, knocked down by heavy rainfall or dehydrated from hot weather before they find a place to hide in the whorl [48]. Larvae also can be killed by several predators, parasites and diseases, such as Beauvaria, that causes a white fungal growth on the dead larvae. Borer survival is estimated to be three borers per egg mass on average. Research has shown that an overall survival rate of 1.3% is sufficient to sustain economic levels of infestation [55]. The USDA issued annual reports for , in which estimates were made of the yearly corn production losses from European corn borer damage [35]. The annual losses varied from a low of 33 million bushels (1952) to over 300 million bushels per year (1949, 1971). (See Figure 28.2) USDA calculated that the average annual loss ( ) of 58 million bushels of corn represented an equivalent loss of 1.8 million acres of corn production [37]. Other estimates of aggregate corn production losses include the years of 1983 and 1995 in Minnesota. For 1983, it was estimated that Minnesota corn growers lost $107 million in corn production because of corn borer damage while in 1995, it was estimated that damage from the European corn borer resulted in $285 million in lost corn 4

5 production in Minnesota [38] [31]. In a 1992 survey in Michigan, 80% of corn growers reported suffering yield losses exceeding five bushels per acre in their fields in the previous ten years [56]. In 1996 it was estimated that annual losses of corn to uncontrolled ECB exceed $1 billion every year [3]. This estimate is based on the 1983 loss estimate from Minnesota of $107 million (cited above) and an assumption that Minnesota represents 10% of the national corn total (based on acreage)[53]. Figures chart ECB densities (larvae/stalk) for Illinois, Wisconsin, Minnesota and Indiana for (IL) and (WI/MN/IN). Southwestern Corn Borer The southwestern corn borer (SWCB) was originally described from a specimen collected in Mexico in The first official records of the presence of the southwestern corn borer in the United States are in 1913 from Lakewood and La Palomas, New Mexico [47]. Eastwardly migration rates of 13 miles per year (1913 to 1931), 20 miles per year (1932 to 1953), and 35 miles per year (1954 to 1964) have been estimated. The primary factors controlling population levels of southwestern corn borer at its northern limits appear to be sub-freezing temperatures and natural enemies. [47] A native of Mexico, being of tropical origin, it thrives in warm weather, but has difficulty surviving the winter in northern areas. This is in contrast to the European corn borer, which being of European origins, is more tolerant to colder weather. In Missouri, the southwestern corn borer is at the northern limits of its distribution and the primary factors controlling populations appear to be freezing temperatures and bird predators. The migration of SWCB across the southern corn belt has been aided by the absence or low populations of natural enemies necessary to keep field populations in check. [47] 5

6 Southwestern corn borer is a major pest of corn in the southern plains states, but its range also extends to neighboring states and beyond. In Kansas, the heaviest infestations have generally been in the southwest and south central areas; in Texas, economic levels occur mainly on the High Plains. Neighboring states Colorado, Nebraska and Missouri report localized damage from SWCB as well. According to scouting reports, SWCB is also fairly common in the southern-most counties of Illinois. In Kentucky, SWCB made a dramatic reappearance in 1993 after a 14-year absence from the state, and in 1995, Mississippi reported isolated cases of SWCB [45]. Figure 28.7 is a national map showing the range of the SWCB. SWCB has two or three generations per year. In most of its range, the southwestern corn borer has at least two generations per year. The full-grown larvae overwinter in the crown of the corn plant just below the soil surface. These larvae pupate in May and early June (months in this section apply to Kansas and the other central states; the high plains of Texas are up to one month earlier) [45]. The moth emerges from the corn stubble about 10 days later. Egg laying occurs during mid-june to early July after which eggs hatch into first-generation larvae. Each female lays from 100 to 400 eggs. First-generation larvae feed in the whorl until they are large enough to tunnel into the stalk. By mid-july, some larvae begin to pupate in the stalk and second-generation moths emerge in late July or early August. Mating and egg laying occur again and secondbrood larvae hatch in August. Larvae feed in the leaf sheath and husk leaves before tunneling into the stalk. Depending on geography and season, these larvae will either overwinter in the base of the corn plant or pupate in the stalk and begin a third generation [45]. Because of their tendency towards cannibalism, usually only one larvae overwinters per plant. This feeding pattern is similar to that of European corn borer (ECB), but there are important differences. Corn seedlings are resistant to ECB but not SWCB. When attacked, these very small corn plants may be severely damaged. Numerous holes in the leaves and leaf breakage due to midrib tunneling are characteristic. Extensive feeding in 6

7 the whorl at this stage of the plant development often results in damage to the growing point (bud) and can result in a dead heart and complete loss of yield by a plant. [42] Second-generation larvae feed in the leaf sheath and between the husk leaves of primary ears when small. After about two weeks, the larvae migrate down the plant and tunnel into the stalk. SWCB characteristically tunnel straight through the middle of the stalk, unlike ECB, which tend to wander through the stalk. [45] Overwintering larvae display a peculiar feeding behavior that can magnify field losses. Larvae migrate down the plant, tunnel into the stalk near the base and begin construction of a hibernation tunnel. In this process they chew a complete or partial groove around the perimeter of the stalk from the inside, leaving only a thin layer of outer rind for support. The hibernation cell is completed by closing the upper part of the tunnel with a silken plug [41]. This girdling of the stalk in the early fall can result in severe lodging. Plants that snap off completely may be impossible to harvest. [45] Losses from southwestern corn borer can occur from dead heart, from larvae tunneling in the stalk and ear and from larval girdling which frequently results in lodged plants. Feeding of first generation SWCB larvae reduced plant height by about 16cm [49]. Grain yield losses of up to 29% in plants infested with first and second generation larvae were recorded. Although these losses resulted from a decrease in the number of kernels per plant, ears harvested from girdled and lodged corn have also been shown to have a lower dry weight and higher water content than those from un-infested corn. [47] A useful cultural practice is fall or early spring plowing or discing to bury or uproot corn stubble and to destroy the overwintering habitat of the southwestern corn borer. This practice increases mortality by exposing larvae to natural hazards and therefore decreases the number of spring moths. The practices of no-tillage or minimum-tillage and of planting winter wheat over corn stubble tend to protect the diapause larvae in their overwintering habitat. [47] 7

8 The highest rate of natural mortality typically occurs among overwintering southwestern corn borers in the stalk crown below ground level. Field observations have shown overwintering mortality ranging from about 50% to >95%. These high mortality rates result in relatively few spring moths and first generation larvae. However, a winter survival rate of 2% in heavily infested areas is adequate to restore population levels in the second generation. [50] Insecticide Treatments There are eight active ingredients recommended for control of European corn borer and southwestern corn borer: chlorpyrifos, lambdacyhalothrin, methyl parathion, permethrin, bifenthrin, carbofuran, esfenvalerate, and Bt microbial insecticides [29] [14]. Insecticides for control of southwestern corn borers generally are the same as those used for European corn borer control. Table 28.2 displays average per acre use rates of these insecticides for ECB/SWCB control. Timing of insecticide application for ECB is critical because sprays are effective only during the two- or three-day period after the eggs hatch and before the larvae bore into the stalks. Once the larvae bore into corn stalks, they are protected from insecticide applications. However, egg laying can occur over a three-week period. Most insecticides are effective for only a 7 10-day period. If application is delayed too long, larvae from the first hatching eggs will have bored into the stalks. If applied too early, the insecticides will have degraded before all the larvae have hatched. Table 28.3 shows the increased yields from five different cornfields in Iowa that received insecticide applications for second generation European corn borer. The increased yield resulting from insecticide treatments ranged from 7 to 33 bushels per acre [3]. These fields were chosen without any indication of the potential for corn borer population. University recommendations for ECB control are based on one carefully timed insecticide application for first generation and one carefully timed application for second generation control. Growers are advised to expect 80% control of first generation larvae 8

9 and 67% control of second generation [14]. The cost of a single insecticide application (including the cost of aerial application) is estimated at $14 per acre [14]. Proper timing of insecticide application for SWCB control is very important because for greatest effectiveness, the larvae must be treated after hatching but before they enter the stalk. Most chemicals require more than one application to achieve acceptable control because of the extended egg-laying period. However, high rates of some of the newer chemicals can provide adequate control with one well-timed application. [43] Bt Corn Bacillus thuringiensis (Bt) is a naturally occurring soil bacterium that produces crystal proteins that selectively kill specific groups of insects [31] Beginning in 1996, several seed companies commercially introduced new corn hybrids that had been altered genetically to produce a Bt protein toxic to corn borers. These hybrids contain a gene from Bacillus thuringiensis kurstaki (Bt), that has been added to the genes in the corn plant to produce a protein not previously present in corn [32]. Corn plants were transformed through a variety of methods, including the use of a gene gun that shoots tiny particles carrying genetic material into cells. The first transgenic Bt corn hybrids were developed to control European corn borer. Corn that expresses the Bt toxin throughout the plant provides excellent control of the SWCB [11], [13]. Research has demonstrated that the SWCB is as susceptible to Bt corn as the ECB. Larvae survival is very low on all transgenic hybrids. [13] Corn borers ingest the Bt protein in trying to feed on the plant. The toxin binds to the gut membranes, and pores are formed. Cells in the gut rupture and the larvae die. Corn borers feed on Bt corn only enough to make a tiny scar (not even a hole) in the corn leaf or sheath. Most borer larvae on Bt corn die within their first day after attempting to feed [3]. 9

10 In order to gain a perspective on the annual value of Bt corn, Monsanto conducted an analysis using the average annual infestation values for ECB in Illinois (Shown in Figure 28.8). The calculation assumes that.25 larva per stalk is first generation with an associated yield loss of 5% per larva. The number of second generation ECB larvae per plant were estimated by the University of Illinois during their annual state pre-harvest corn borer surveys. Using this methodology, the percent yield loss per acre was calculated for each year. These estimates were multiplied by the annual average value of a bushel of corn and the average yield of corn per acre to determine the income loss per acre from uncontrolled ECB. It is assumed that if Bt corn had been planted, the yield loss would have been reduced by 96% at a cost of $8 per acre. For 1997 and 1998, the Monsanto calculation relies on the actual bushel per acre advantage recorded for Bt corn in Illinois. By subtracting the price premium of the Bt corn from the value of the predicted yield increase in Illinois, estimates were made of the average annual per acre value of Bt corn in Illinois for each year These values are shown in Figure In 10 of the 13 years , corn growers would have achieved a net positive return of $4 per acre to $37 per acre. In three years (including 1998), the net return would have been a loss because of extremely low borer populations in those years. A similar analysis using historical ECB damage data for Minnesota gave similar results. The projected benefits averaged $17.24 per acre, significantly exceeding the assumed selling price of $7-10 per acre [31]. However, in low infestation years (5 years), the yield protection provided by Bt corn barely covered the cost of the seed while during high infestation years (3 years), the values of the yield increases ($28-$50 per acre) were four to five times the added seed cost. As part of the process of reregistering the Bt corn varieties, EPA estimated the aggregate benefits to US growers of planting Bt corn [12]. EPA estimated aggregate benefits to range from $38 million in a year of low borer pressure to $219 million in a year of high borer infestation. EPA s estimates are shown in Table The EPA analysis is based on Bt corn adoption on 17.9 million acres, a technology fee of $8/A, and a price of corn 10

11 of $1.87/bu. EPA assumes that farmers gain 5.4 bushels/a in a low infestation year and 10.8 bushels/a in a high year. Numerous studies have estimated the increases in corn yields due to Bt corn adoption since These studies results have been largely determined by the extremely low population of the ECB in Midwestern states ( ) (see Figures ). However, many entomologists regard the years as extremely unusual and not typical of long-term normal ECB populations which began to increase in 2001 (see Figures ). The low levels of ECB seen in 1998 to 2000 were the result of an unusual weather pattern in the spring of 1998 that caused a collapse in the population. European corn borer adults require corn plants with a minimum of 5 expanded leaves to deposit eggs and larval survival is very low on plants less than 24 inches (7leaves) [23]. In 1998, a weather pattern that occurred across most of the Corn Belt, Northeast and Mid-Atlantic states prevented timely planting during late April and most of May. This delayed the majority of corn field s planting until late May and early June when typical planting is late April and early May. While corn planting was delayed, overwintering European corn borer development was accelerated due to warm temperatures that accompanied the rain [23]. Typically, during this time rain brings cooler temperatures that slow ECB development. The result of this rare combination of events was that adult ECB emerged early and the flight was completed by the time that cornfields had reached a stage to allow successful colonization and survival of larvae. Therefore, adult ECB either died or were forced to deposit their eggs on less desirable hosts that lead to high larval mortality. Once the populations collapsed, it required several years for them to recover. This recovery is now occurring across these corn production areas. [23] Entomologists in states where the SWCB is the major pest (CO, AR, KS, KY, LA, OK, TN, TX) indicated that the years were not unusually low as they were in the Midwest where ECB is the major pest. 11

12 Estimated Impacts USDA has published estimates for 11 states of corn acreage planted to Bt corn in 2001 [1]. These estimates are shown in Table 28.5 along with adoption estimates for the other 25 major corn-producing states, which were provided, by Extension Service Specialists and Monsanto. It is estimated that national adoption of Bt corn represents 14.9 million acres or 21 % of national corn acreage. A survey of extension service entomologists was undertaken for information on corn yield impacts due to ECB/SWCB infestations during a low and a high infestation year. These estimates for the 36 states are shown in Table Yield losses in high infestation years are typically significantly higher in Plains states and in other states where SWCB is the primary pest (CO, KS, OK, KY, TX). The specialists were also asked for estimates of the number of years out of a normal 10- year period that would be classified as low or high. These estimates are also shown in Table There is only one state (AL) where no yield loss typically occurs to corn borers (all years are classified as low during which the average yield loss is zero). In order to estimate the Bt corn price premium paid by US farmers, two companies supplying Bt corn seed were contacted. Internal seed corn price data from Syngenta and Monsanto indicated a 2001 Bt seed corn premium of $6.55/A and $6.67/A respectively [74], [73]. These estimates take into account technology fees, seed premiums, rebates, discounts and giveaways. The methodologies used by the companies are delineated in Table 28.APP-01 which also includes a discussion that compares these companies estimates with estimates used in other recent impact studies. Table 28.7 displays state-by-state estimates of the aggregate impacts on corn production volume and value and production costs of current adoption of Bt corn during a low and high borer infestation year. These estimates compare the impacts of Bt corn adoption to an untreated condition i.e. no use of insecticides. Growers who plant Bt corn are assumed to gain 100% of the bushels of corn that would otherwise be lost to borers 12

13 during a high or low year (see Table 28.6). In comparison to an untreated scenario, total production increase on current Bt acreage is estimated at 72 million and 244 million bushels during a low and high year respectively. The cost of the Bt technology is estimated at $6.50/A and the value of corn is estimated at $2/bu. The total value of the increased production is estimated at $145 million and $489 million in a low and high year respectively. The net aggregate benefit of planting Bt corn after subtracting the Bt corn technology cost is estimated at $48 million and $392 million in low and high years respectively. These estimates are higher than EPA s estimates of $37.8 and $219.9 million in low and high years respectively (see Table 28.4). This is due to the inclusion of states such as Texas where the primary pest is SWCB and the potential yield loss (8 40 bu/a) is much higher that EPA s estimates (5-11 bu/a). Table 28.8 simulates the use of insecticides on current Bt corn acreage. Insecticides provide 80% control of corn borers at a cost of $14/A. The use of insecticides is simulated on Bt corn acreage for a high infestation year only because in no state does insecticide use return more than the $14/A cost in a low year. The highest gain in a low year from using Bt corn and achieving 100% control is $16/A (in TX and OK)[see Table 28.7]. Since insecticides provide only 80% control, the increased yield from insecticide use would be valued at $12.80/A which does not justify the $14/A cost. Table 28.8 shows state-by-state estimates of the potential per acre yield and value increase that would result from using insecticides in a high infestation year. Of the 36 states, there are only three states (AL, IN, MS) for which an insecticide application during a high year would not deliver $14/A in increased total production value. Table 28.8 shows the net increase in income after subtracting out the cost of the insecticide treatment. It is estimated that during a high year that insecticide use would increase net income by$183 million. Also shown in Table 28.8 are insecticide use estimates: during a high infestation year, 5.6 million lbs. of insecticides would be applied. Table 28.9 displays estimates of the impacts of current adoption of Bt corn during a typical year out of a normal 10-year cycle. The table includes estimates of the number of years out of 10 which are classified as low and high. For all states, the increase in production volume and value, and production costs for a low infestation year are based on the use of Bt corn. For high infestation years, the impact of Bt corn is calculated as the 13

14 difference between volume, value and cost resulting from the planting of Bt corn minus the amounts which would result from the use of insecticides (except for AL, IN, MS for which the amounts resulting from Bt corn adoption in a high year are assigned). Thus in a high year, growers only gain from Bt corn the extra 20% yield improvement that they would not gain from using insecticides. Bt corn is credited with lowering production costs during a high infestation year because Bt corn costs less than insecticides. The production volume and value and the production cost estimates for low and high years are weighted by the number of low and high years expected in a normal 10 year cycle to compute estimates for a typical year. Insecticide use is assumed to occur only in high years. The use of insecticides in a typical year is calculated as the product of the number of high years times the estimated insecticide use in a high year divided by ten. The net value of Bt corn adoption during a typical year out of ten is calculated as the difference between the increase in production value and the increase in production costs. It is estimated that during a typical year, on currently planted acreage (14.9 million), Bt corn results in an increase of 63 million bushels of corn valued at $126 million. The increased cost of Bt corn in the typical year is estimated at $1.1 million which reflects the reduction in cost that Bt corn provides in high infestation years compared to insecticide use. Thus, the net value of Bt corn is estimated at $125 million in a typical year. Without the use of Bt corn, approximately 2.6 million pounds of insecticides would be used in a typical year. 14

15 Table 28.1 Corn for Grain: 2000 State Harvested (000A) Yield (BU/A) Production (Million Bushels) Price Per Bushel ($) Value of Production (Million $) AL AZ AR CO CT DE GA IL IN IA KS KY LA MA MD MI MN MS MO NE NJ NM NY NC ND OH OK PA SC SD TN TX VA VT WV WI Total US Total Source: [19] [22] 15

16 Table 28.2 Insecticide Use Rates: European Corn Borer/Southwestern Corn Borer (LB AI/A) Bifenthrin 0.07 Carbofuran 1.00 Esfenvalerate 0.04 Chlorpyrifos 1.00 Lambdacyhalothrin 0.02 Methyl Parathion 0.75 Permethrin 0.17 Bt - Source: [29] Table 28.3 Yield Increases from Insecticide Treatment for Second Generation ECB in Iowa Year Insecticide LB AI/A Bushels Per Acre Increase Untreated Treated Bu/A % 1991 Methyl Parathion Fonofos Methyl Parathion Permethrin Chlorpyrifos Source: [3] Fields received one insecticide application for second generation corn borer Table 28.4 Grower Benefits of Bt Field Corn (EPA Estimates) Item Unit Low Insect Pressure 1 High Insect Pressure Acres Bt Corn (000) 17,933 17,933 Yield Increase (bu/a) Value of Yield Increase ($/bu) ($/A) Technology Fee ($/A) Net Benefit ($/A) Total Net Benefit (000 $) 37, ,979 Source: [12] 1 EPA states this is intended to be representative of the lower bound benefits and points out that unusual conditions could result in actual benefits below the lower bound estimates in some years. 16

17 Table 28.5 BT CORN ADOPTION: 2001 State Harvested (000A) %Bt Bt Acres (000A) Source AL Flanders [2] AR Johnson [4] AZ Mattingly [51] CO Peairs [5] CT Mattingly [51] DE Whalen [6] GA Buntin [7] IL USDA [1] IN USDA [1] IA USDA [1] KS USDA [1] KY Bessin [8] LA Riley [65] MA Mattingly [51] MD Dively [9] MI USDA [1] MN USDA [1] MS Stewart [15] MO USDA [1] NE USDA [1] NJ Ghidiu [64] NM Mattingly [51] NY Waldron [61] NC Van Duyn [16] ND Glogoza [17] OH USDA [1] OK Royer [21] PA Calvin [23] SC Manley [24] SD USDA [1] TN Patrick [25] TX Porter [26] VA Youngman [63] VT Mattingly [51] WV Mattingly [51] WI USDA [1] Total

18 Table 28.6 Corn Borer Incidence and Yield Impacts 1 State Yield Loss (bu/a) # Of Years* Source Low High Low High AL Flanders [2] AR Johnson [4] AZ Assigned CO Peairs [5] CT Assigned DE Whalen [6] GA Buntin [7] IL Steffey [27] IN Bledsoe [28] IA Rice [70] KS Buschman [30] KY Bessin [8] LA Riley [65] MA Assigned MD Dively [9] MI Assigned MN Ostlie [33] MS Stewart [15] MO Assigned NE Hunt [62] NJ Ghidiu [64] NM Assigned NY Waldron [61] NC Van Duyn [16] ND Glogoza [17] OH Eisley [39] OK Royer [21] PA Calvin [23] SC Manley [24] SD McLeod [44] TN Patrick [25] TX Porter [26] VA Youngman [63] VT Assigned WV Assigned WI Wedberg [40] * # of years out of 10 1 Includes European and Southwestern corn borer. 18

19 Table 28.7 Aggregate Impacts of Bt Corn Adoption 1 State Bt Acreage Production Volume Increase Production Value Increase 2 Bt Cost 3 Total Net Value 000 A Bu/A 000 Bu/Year $/A 000$/Year 000 $/Year 000 $/Year Low High Low High Low High Low High Low High AL AR , , ,264 AZ CO , ,988 6, ,065 5,609 CT DE , GA IL 1, ,744 14, ,488 28,720 9,334 2,154 19,386 IN , ,998 4,662 2, ,498 IA 3, ,600 34, ,200 68,640 20,280 10,920 48,360 KS ,320 34, ,640 69,120 5,616 3,024 63,504 KY , ,082 9,299 1, ,700 LA , , ,996 MA MD , ,616 5, ,596 MI , ,576 4,728 1, ,448 MN 1, ,613 24, ,226 49,764 12,441 4,785 37,323 MS MO ,325 19, ,650 39,900 4,323 2,328 35,578 NE 2, ,465 23, ,930 46,046 13,605 7,326 32,442 NJ NM , NY NC ND , ,670 3,674 1, ,589 OH , ,544 1, ,043 OK , ,344 3, ,478 PA , ,426 4,968 1, ,564 SC SD 1, ,350 19, ,700 38,100 8,255 4,445 29,845 TN , ,470 3, ,279 TX ,600 38, ,200 76,000 6,175 9,025 69,825 VA VT WV WI ,320 3, ,640 7,920 2, ,775 Total , , , ,962 97,026 48, ,936 1) Compared to Untreated 2) Calculated at $2/Bushel 3) Calculated at $6.50/Acre 19

20 Table 28.8 Aggregate Impacts of Simulated Insecticide Use for Corn Borer Control (High Infestation Year) State Bt Acreage Production Increase Insecticide Cost 3 Total Net Value Insecticide Use Volume Value 1000 A Bu/A Bu/Yr $/A $/Yr 000 $/Yr $/A 000 $/Yr Lbs./Yr 4 AL AR , , ,074 23,180 AZ ,040 CO , ,226 1, ,238 53,960 CT ,900 DE , ,560 GA ,000 IL 1, , ,976 20, , ,680 IN , , IA 3, , ,912 43, ,232 1,185,600 KS , ,296 12, , ,320 KY , ,439 3, ,995 93,480 LA , , ,904 21,280 MA MD , ,202 1, ,788 38,380 MI , ,782 2, ,024 74,860 MN 1, , ,811 26, , ,320 MS MO , ,920 9, , ,700 NE 2, , ,837 29, , ,340 NJ ,920 NM ,120 NY ,020 NC ,160 ND , ,939 2, ,460 OH , ,435 3, ,201 87,780 OK , ,419 1, ,243 31,920 PA , ,974 3, ,080 SC ,320 SD 1, , ,480 17, , ,600 TN , ,587 2, ,860 TX , ,800 13, , ,000 VA ,080 VT ,520 WV WI , ,336 4, , ,400 Total 14, , , , ,425 5,574,980 1) Calculated at 80% of the increase attributed to Bt Corn (see Table 28.7) 2) Calculated at $2/Bushel 3) Calculated at $14/Acre 4) Calculated at 0.38 Lbs.Ai/Acre 20

21 Table 28.9 Aggregate Impacts of Bt Corn Adoption: Typical Year State # Years out of 10 Production Volume Increase Production Value Increase Production Cost Net Value Insecticide Use 000 Bu/Year 000 $/Year 000 $/Year 000 $/Year Lbs./Y Low High Low High Typical Low High Typical Low High Typical Typical Typical AL AR ,590 AZ ,520 CO ,988 1,306 1, , ,718 26,980 CT DE ,780 GA IL 5 5 5,744 2,872 4,308 11,488 5,744 8,616 9,334-10, , ,840 IN ,331 1,532 1,998 4,662 3,064 2,165 2,165 2, IA ,600 6,864 11,232 31,200 13,728 22,464 20,280-23,400-1,560 24, ,800 KS 5 5 4,320 6,912 5,616 8,640 13,824 11,232 5,616-6, , ,160 KY ,082 1,860 1,471 1,599-1, ,594 46,740 LA ,384 MA MD ,616 1,050 1, ,299 15,352 MI , ,135 1,281-1, ,785 52,402 MN 6 4 8,613 4,976 7,158 17,226 9,953 14,317 12,441-14,355 1,723 12, ,928 MS MO 5 5 3,325 3,990 3,658 6,650 7,980 7,315 4,323-4, , ,350 NE ,465 4,605 8,707 20,930 9,209 17,414 13,605-15,698 4,814 12, ,602 NJ ,044 NM ,560 NY ,510 NC ,728 ND , ,389 1,086-1, ,005 19,038 OH , ,502-1, ,556 OK , ,016 15,960 PA , ,296 1,404-1, ,624 SC ,064 SD 5 5 6,350 3,810 5,080 12,700 7,620 10,160 8,255-9, , ,300 TN , , , ,758 TX 2 8 7,600 7,600 7,600 15,200 15,200 15,200 6,175-7,125-4,465 19, ,800 VA VT WV WI 3 7 1, ,640 1,584 1,901 2,145-2,475-1,089 2,990 87,780 Total: 72,642 51,016 63, , , ,465 97, ,479 1, ,356 2,603,456 Low: Aggregate increase from Bt corn compared to untreated. High: Difference between aggregate increase from Bt corn and aggregate increase from insecticide use. Typical: Low and High aggregate values weighted by the number of low and high years. Insecticide Use: Use in high year weighted by the number of high years divided by

22 Figure 28.1 European Corn Borer Infestation Low Medium High Source: [34] Figure 28.2 U.S. Corn Production Losses: European Corn Borer Damage MILLION BU/YR Source: [35] [36] [37] 22

23 Figure 28.3 European Corn Borer Populations, Illinois 5 4 Larvae/ Stalk Source: [20] [71] [72] [52] [54] Figure 28.4 European Corn Borer Populations, Wisconsin 5 4 Larvae/ Stalk Source: [57] [58] 23

24 Figure 28.5 European Corn Borer Populations, Minnesota 5 4 Larvae/ Stalk Source: [59] Figure 28.6 European Corn Borer Populations, Indiana 5 4 Larvae/ Stalk Source: [60] 24

25 Figure 28.7 Southwestern Corn Borer Affected Area Source: [10] Figure 28.8 Average Return From Bt Corn in Illinois (Monsanto Estimates) $40.00 $37.24 $32.75 $30.00 $25.36 $/A $20.00 $13.32 $13.87 $10.00 $9.20 $9.64 $7.79 $8.05 $3.56 $0.00 -$ $0.71 -$2.12 -$ Source: [72] 25

26 Table 28.APP-01 Bt Seed Corn Price Data In order to estimate the Bt corn price premium paid by US farmers, two companies supplying Bt corn seed were contacted. Internal seed corn price data from Syngenta and Monsanto indicated a 2001 Bt seed corn premium of $6.55/A and $6.67/A respectively [74], [73]. These estimates take into account technology fees, seed premiums, rebates, discounts and giveaways. One company (Syngenta) analyzed proprietary seed corn price data from Doane s [69]. For this comparison, seed corn price data were filtered to exclude Bt varieties that were stacked with herbicide tolerant traits (Roundup Ready and Liberty Link). (The assumption being that some of the increased price for these varieties is due to the herbicide tolerant trait.) The Doane data were filtered further to include only those corn varieties (Bt and nonbt) from the major companies selling Bt corn varieties (Asgrow, Cargill, Dekalb, Garst, Golden Harvest, Pioneer, Mycogen and Syngenta). (The assumption being that growers selecting a Bt corn variety would most likely be comparing the cost and performance of varieties (Bt and nonbt) marketed by the same companies. This analysis of the Doane data resulted in an estimated price premium for Bt corn of $6.50/A [69]. This estimate ($6.50/A) is consistent with a recent analysis from North Carolina State University ($6-8/A)[68]. The $6.50/A estimate is higher than that reported in a recent survey of Iowa corn farmers conducted by Iowa State University s Leopold Center ($4/A) [67]. The estimate is lower than an estimate of $9/A used in a recent report from Benbrook Consulting Services [66]. The Benbrook estimate was calculated based on an analysis of the Doane seed corn price database. However, the adjustments described above were not made: the value of the herbicide tolerant stacked Bt varieties were included which inflates the average Bt corn price. In addition, all companies were included in the Benbrook analysis, which tends to deflate 26

27 the price of the non-bt corn varieties because several companies specialize in sales of extremely low price seed corn. However, it is not likely that growers who purchase Bt corn seed make price comparisons that include these low cost seed corn varieties. As noted above, it is believed that the most relevant analysis is to compare prices of all the corn varieties offered by the same companies that sell Bt corn seed. The Benbrook report also uses a second method relying on Doane data, which also results in an estimated $9/A price premium for Bt corn seed. Benbrook identified paired seed corn varieties (Bt and non-bt), which have the same isoline identification number. The comparison indicates that the Bt enhanced versions of the isolines were priced approximately $9/A higher than the non-bt original isoline varieties. This analysis is not an accurate way of measuring the increased price that growers pay for Bt corn seed since the choice they make is not usually in comparison to the original isoline without the Bt trait. Following the introduction of the original isoline, there is usually a 1-2 year period during which the Bt corn enhanced version of the isoline is under development. During this time period, other new non-bt isolines are also typically introduced. Thus, when the Bt corn variety has been introduced, the set of choices has expanded to include not only the original isoline but also new non-bt cultivars. The grower typically chooses between the Bt corn variety and a new non-bt variety, which is priced higher than the earlier variety. Thus, the price gap between Bt corn varieties and non-bt corn varieties is less than a simple comparison to the original isoline would suggest. 27

28 References 1. USDA, Acreage, National Agricultural Statistics Service, June Flanders, Kathy, Auburn University, personal communication. 3. Mason, Charles E., et al., European Corn Borer: Ecology and Management, North Central Regional Extension Publication no. 327, Iowa State University, January Johnson, William, University of Arkansas, personal communication. 5. Peairs, Frank, Colorado State University, personal communication. 6. Whalen, Joanne, University of Delaware, personal communication. 7. Buntin, Dave, University of Georgia, personal communication. 8. Bessin, Ric, University of Kentucky, personal communication. 9. Dively, Galen, University of Maryland, personal communication. 10. Davis, Frank M., Economic Status of Southwestern Corn Borer, December, Flanders, Kathy L., Status of Transgenic Crops for Control of Insects Other Than the European Corn Borer, in 2000 Proceedings Illinois Crop Protection Technology Conference. 12. EPA, Bt Plant Incorporated Protectants Biopesticides Registration Action Document, Office of Pesticide Programs, October Williams, W. Paul, et al, Transgenic Corn Evaluated for Resistance to Fall Armyworm and Southwestern Corn Borer, Crop Science, May-June, Illinois Agricultural Pest Management Handbook, University of Illinois Extension. 15. Stewart, Scott, Mississippi State University, personal communication. 16. VanDuyn, John, North Carolina State University, personal communication. 17. Glogoza, Phil, North Dakota State University, personal communication. 18. USDA, Feed Situation and Outlook Yearbook, Economic Research Service, FDS-1998, April USDA, Crop Values 2000 Summary, National Agriculture Statistics Service, February

29 20. Briggs, S.P. and C.A. Guse, Forty Years of European Corn Borer Data: What Have We Learned?, in 38th Illinois Custom Spray Operators Training Manual, Cooperative Extension Service, University of Illinois, Royer, Tom, Oklahoma State University, personal communication. 22. USDA, Crop Production 2000 Summary, National Agricultural Statistics Service, January Calvin, Dennis, Pennsylvania State University, personal communication. 24. Manley, Don, Clemson University, personal communication. 25. Patrick, Charles, University of Tennessee, personal communication. 26. Porter, Patrick, Texas A&M University, personal communication. 27. Steffey, Kevin, University of Illinois, personal communication. 28. Bledsoe, Larry, Purdue University, personal communication. 29. Field Corn Insect Management 2001, Kansas State University, Cooperative Extension Service, Entomology Buschman, Larry, Kansas State University, personal communication. 31. Ostlie, K. R., et al., BT Corn and European Corn Borers: Long Term Success Through Resistance Management, North Central Regional Extension Publication, NCR602, University of Minnesota, Sloderbeck, Phil, et al., Corn Borer Management Using BT Corn, Cooperative Extension Service, Kansas State University, MF-2175, December Ostlie, Ken, University of Minnesota, personal communication. 34. Martin, Marshall A. and Jeffrey Hyde, Economic Considerations for the Adoption of Transgenic Crops: The Case of Bt Corn, Journal of Nematology, December, USDA, Cooperative Economic Insect Report, APHIS, Vol. 25, No. 32, August 8, USDA, Estimates of Damage by the European Corn Borer to Grain Corn in the United States in 1951, Cooperative Economic Insect Report, Special Report No. 5, July 26, USDA, Losses in Agriculture, ARS-20-1,

30 38. Noetzel, D.M., et al., Estimated Annual Losses Due to Insects in Minnesota , University of Minnesota, Agricultural Extension Service, AG-BU- 2541, Eisley, Bruce, Ohio State University, personal communication. 40. Wedberg, John, University of Wisconsin, personal communication. 41. Sloderbeck, Phillip, et al, Southwestern Corn Borer, Cooperative Extension, Kansas State University, July Bessin, Ric, Southwestern Corn Borer, University of Kentucky, Entomology, Revised 10/ Sloderbeck, Phil, and Larry Buschman, Management Options for the Southwestern Corn Borer, in 2000 Proceedings Illinois Crop Protection Technology Conference. 44. McLeod, Murdick, Pioneer, personal communication. 45. Butzen, Steve, Southwestern Corn Borer Management, available at Karr, Doyle, Pioneer, personal communication. 47. Chippendale, G. Michael and Clyde Sorensen, Biology and Management of the Southwestern Corn Borer, available at Beck, Stanley D., Developmental and Seasonal Biology of Ostrinia nubilalis, Agricultural Zoology Review, November Scott, G. E., and F. M Davis, Effect of Southwestern Corn Borer Feeding on Maize, Agronomy Journal, 66, , Wilbur, D. A., H.R. Bryson, and R.H. Painter, Southwestern Corn Borer in Kansas, Kansas Agricultural Experiment Station Bulletin 339, Mattingly, John, Monsanto, personal communication 52. Gray, Mike and Keven Steffey, Overwintering Populations of European Corn Borers Remain Very Low in Illinois, Pest Management and Crop Development Bulletin, November 3, Mason, Charles, University of Delaware, personal communication. 30