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Potential Benefits and Limitations of Transgenic Bt Corn for Management of the European Corn Borer (: )

MARLIN E. RICE AND CLINTON D. PILCHER Downloaded from https://academic.oup.com/ae/article/44/2/75/2474575 by guest on 27 September 2021

HE ADVENT OF TRANSGENIC, OR GENETI- ation tunneling in blister or dough- Potential Benefits of Bt Corn Tcally engineered, corn to reduce in stage corn can cause a 2-3 % yield loss (Bode sect damage will alter integrated man- and Calvin 1990). Yield losses caused by Control of European Corn Borer. Cur- agement dramatically in the Corn Belt. The second-generation borers in 18 rently, commercial Bt corn hybrids contain term 'transgenic corn' broadly describes trials over a 7-year period in Iowa ranged one of two genes that express plants that contain genetic material from from 0.9-32.6 bushels per acre more than CrylAb or CrylAc, and another Bt , another species. One of the new genes in in the untreated controls (Rice 1994a, b, c Cry9C, may be available soon. Before the Bt transgenic plants produces a protein that ei- and unpublished data); 16 of the 18 fields gene is inserted into corn, a genetic promot- ther kills or retards development of an in- (89%) had yield losses that exceeded 4 er is attached to the Bt gene that regulates sect. Consequently, control is pro- bushels per acre. The average yield loss when and where the gene functions inside duced by the plant with no additional input caused by these borers was 9.3 bushels, but the corn plant. When the modified Bt gene is from the farmer. Because corn is grown on may have been greater because inserted into another organism, such as 75 million acres in the United States, trans- rarely provide 100% control. corn, the transformation is known as an genic corn hybrids likely will have a tremen- Iowa and Minnesota farmers' percep- event. CrylAb has been transformed into dous impact on crop production and pro- tions about damage caused by European several genetic events by several seed compa- tection. Although transgenic corn will not corn borers were that yield losses were much nies. Hybrids with the YieldGard® technol- be a 'silver bullet' capable of solving all of larger than we observed in our trials. Sixty- ogy (events Btll or MON810) provide our corn insect pest problems, the strategies five percent and 69% of farmers thought 98% control of first- and second-genera- for managing potentially could move that first- and second-generation larvae, re- tion European corn borers. Hybrids with in a direction that is radically different from spectively, caused serious economic yield KnockOut® or NatureGard® technology traditional methods. loss (Rice and Ostlie 1997). Their percep- (event 176) control 98% of first-generation In 1996, farmers had their first oppor- tion was that first-generation damage aver- borers but only 50-75% of second-genera- tunity to plant transgenic corn hybrids that aged 15.2 bushels per acre and second-gen- tion larvae (Ostlie et al. 1997). Hybrids with killed European corn borers, nubi- eration damage averaged an addition a] 15.3 the and Cry9C genes had not been lalis (Hiibner). This transgenic corn con- bushels per acre, for a total of 30.5 lost tested extensively. tains a modified gene from the soil bacteri- bushels per acre. Ironically, only 35.2% of Yield Protection. The Bt protein pro- um thuringiensis Berliner. A protein the farmers had scouted their fields and tects the corn plant from European corn produced by B. thuringiensis is toxic to used economic thresholds, and even fewer borer injury and the yield loss associated some insects. Scientists isolated the protein- (28.7%) had used an insecticide for control with stalk tunneling. In 14 field trials in producing gene, modified it, and inserted it of European corn borers. Iowa during 1997, 9 near-isogenic non-Bt into corn (Koziel et al. 1993). This transgen- These yield losses, whether real or per- hybrids averaged 140.1 bushels per acre ic corn commonly is caned Bt corn. Bt corn ceived, illustrate the potential influence while 9 Bt hybrids averaged 147.7 bushels produces the protein that causes European European corn borers can exert on crop per acre; a yield protection of 7.6 bushels corn borer larvae to die after they feed on management decisions. Unfortunately, fu- per acre. At 3 locations in Minnesota in the plant. The protein protects the corn ture yield losses cannot be stated accurately 1997, Bt hybrids averaged 171.8 bushels plant from large amounts of leaf feeding, because insect densities, crop response to in- per acre; near-isogenic non-Bt hybrids aver- stalk tunneling, and subsequent yield loss jury, and environmental conditions are un- aged 153.6 bushels per acre, an average caused by European corn borer. predictable. The damage potential of the Eu- yield protection of 18.2 bushels per acre The European corn borer is one of the ropean corn borer and the genesis of (Ken Ostlie, personal communication). Ex- most damaging pests of field corn in the transgenic plants necessitates a review of the tremes in yield protection between Bt and United States with yield losses and control utility of Bt corn for management of this in- non-Bt hybrids have ranged from no differ- expenditures costing farmers more than 1 sect. We present a brief summary of the po- ence to 23 bushels per acre in Nebraska billion dollars annually (Mason et a!. 1996). tential benefits and limitations of Bt corn for (Echtenkamp et al. 1997), 37.4 bushels per Two generations of this insect usually occur management of the European corn borer acre in Iowa (Rice 1997), and 47.1 bushels throughout the Corn Belt. A single first-gen- based upon our interpretations of research per acre in Minnesota (Ken Ostlie, personal eration larva tunneling in whorl-stage corn conducted in the Corn Belt during the past 4 communication). In Kansas, where the Eu- can cause a 5-6%yield loss; a second-gener- years. ropean corn borer and southwestern corn

AMERICAN ENTOMOLOGIST • Summer 1998 75 borer, Diatraea grandiosella Dyar, are sym- 1995). Three of the most common Euro- Belt. Volunteer corn plants that emerge in patric, maximum yield protection attributed pean corn borers predators, the green the following year are weeds. A de- to Bt hybrids has ranged from 35.9 bushels lacewing Chrysoperla carnea Stephens, in- crease or elimination of tunneling in the ear per acre (Buschman et al. 1997a) to 80.5 sidious flower bug, Say, shank means that fewer corn ears will drop bushels per acre (Buschman et al. 1997b). and the lady to the ground before harvest and fewer ker- The Bt gene does not increase yield in a hy- DeGcer, also consume pollen. In laboratory nels will germinate as volunteer corn in next brid; it protects the hybrid's genetic yield studies, pollen from Bt corn was nontoxic to year's soybean crop. A reduction in volun- potential by reducing the amount of leaf in- these three predators and did not delay de- teer corn would decrease the time, energy, jury and stalk tunneling caused by Euro- velopment of immature stages or longevity and amount of expensive herbicides used to pean corn borers, and, in some states, of adults (Pilcher et al. 1997a). In field stud- eliminate volunteer corn. southwestern corn borers. ies, pollen from Bt corn also did not affect Reduced Frequency of Incidence of Ear Reduced Insecticide Use and Hazards. these three predators where the predators' and Stalk Rots. European corn borer larvae Insect management with Bt corn likely will population densities were similar in both Bt often are associated with the disease cycles reduce the amount of handling and applica- and non-Bt corn fields. of ear rot and stalk rot pathogens. The inter- tion of synthetic insecticides. Replacement Areawide Suppression of European action between the larvae and pathogenic of insecticides with Bt corn will reduce expo- Corn Borers. Catastrophic mortality of a fungi can occur in 3 ways (Munkvold

sure to insecticides, increase the safety of population of first-generation corn borers 1998): (1) plant injury by the larvae can Downloaded from https://academic.oup.com/ae/article/44/2/75/2474575 by guest on 27 September 2021 farm workers, and avoid misapplication or would result in very few insects surviving to open infection sites for fungi; (2) larvae can drift of chemicals onto nontarget or residen- subsequent generations. The overall popu- act as vectors of pathogenic fungi, carrying tial areas. Real or perceived problems asso- lation equilibrium should decline rapidly in the directly into the plant; and (3) lar- ciated with insecticide use (e. g., threats to an area if farmers plant Bt corn for several vae can stress the plant and make it more human health and food quality) should de- seasons, the ratio of Bt to non-Bt corn acre- susceptible to infection and disease. Hybrids crease. The Bt gene as a plant in age increases, and relatively few alternate expressing Cry1Ab in kernels had a 58- corn has no known or foreseeable human hosts are available. 87% reduction in the incidence of ear rot health hazards (Environmental Protection Reduced Scouting Costs. Some genetic and a 17-38% reduction in the incidence of Agency 1995). events kill almost all European corn borer kernel infection (Munkvold et al. 1997). Reduced Control Costs. Farmers cur- larvae, whereas other events kill almost all Less tunneling by larvae in the ear tip and rently pay a technology fee, or premium first-generation larvae and most second- stalk results in fewer entry points for corn price, of $5-12 per acre for Bt corn hybrids. generation larvae. Scouting for purposes of disease pathogens such as Gibberella and This added cost, however, is less than or making control decisions should not be nec- Fusarium. The end result is cleaner ears with equal to the cost of a commercial application essary because the density of surviving lar- higher quality grain and decreased potential of a synthetic insecticide (Tracy Cameron, vae should be low and unlikely to exceed an for the development of mycotoxins. personal communication). The added bo- economic threshold requiring other man- Reduced Stalk Lodging and Harvest nus for transgenic hybrids is that protection agement practices (i.e., insecticides). Howev- Loss. Stalks with fewer tunnels or without is provided against multiple generations of er, scouting would be beneficial for assessing tunnels caused by second-generation Euro- European corn borers, whereas an insecti- efficacy of the Bt hybrid and monitoring the pean corn borers stand better in the field at cide provides partial control only of one development of resistant insects. harvest. Preharvest loss would be reduced generation. Control of Other Insects. The corn ear- because fewer ears would fall to the ground. Proper Timing of Control. Proper tim- worm, Helicoverpa (Boddie), and south- Additionally, standing corn can be left long- ing of the application of an insecticide is crit- western corn borer can be serious pests of er in the field to dry, thereby reducing drying ical for maximum efficiency. An insecticide field corn in the south-central and southern costs. application generally provides residual con- United States. Although the corn earworm trol of European corn borers for 7-10 days; occasionally feeds in whorl-stage corn, lar- Potential limitations of Bt Corn however, even 67-80% mortality of larvae vae cause the greatest damage when they is the best that can be expected under good feed on developing kernels. The southwest- Unpredictability of European Corn Bor- conditions (Mason et al. 1996). Bt corn ex- ern corn borer is predominantly a leaf-feed- er Densities. Bt corn is planted as a preven- presses the Bt protein throughout most of ing and stalk-tunneling pest. However, after tive tactic for 1-3 generations of an insect the growing season, thereby averting the it enters the stalk, it often girdles the plant that will occur several months in the future. concern about timing of application. causing it to fall to the ground where the ear Because the purchase of Bt corn is an invest- No Secondary Pest Outbreaks. Insecti- cannot be harvested. The amount of protec- ment made before planting time, the need cides used to control European corn borers tion provided by Bt corn against these two for this management tool cannot be predict- in the western Corn Belt can create out- species varies depending on the Bt event. ed before European corn borers lay their breaks of secondary pests such as Banks Genetic events MON810 and Btll provide eggs. grass mite, Oligonychus pratensis (Banks), nearly complete control. Corn hybrids with Economic Return Is Not Guaranteed. and twospotted spider mite, Tetranychus event 176 show increased protection rela- An economic return for Bt corn is realized urticae Koch, requiring additional applica- tive to susceptible non-Bt hybrids, but com- only if the density of European corn borers tions of . Bt corn diminishes the plete control is not achieved and some ker- is large enough to cause economic loss great- need for insecticides, which should reduce nels are destroyed by corn earworms er than the premium paid for the transgenic the frequency of outbreaks of secondary (Pilcher et al. 1997b). Likewise, southwest- hybrid. A large number of European corn pests. ern corn borers in event-176 hybrids may borer eggs laid in a field increases the "val- Environmental Safety. and in- girdle stalks late in the growing season. ue" of Bt corn. However, if a low density of sect predators that might occur in Bt corn Reduced Amounts of Volunteer Corn results in very few eggs deposited in a should not be adversely affected by the Bt and subsequent herbicide use. Corn com- Bt corn field, then the economic investment protein (Environmental Protection Agency monly is rotated with in the Corn in the biotechnology was unnecessary.

76 AMERICAN ENTOMOLOGIST • Slimmer 1998 Variable Yield Performance. Grain yield purchase price of a Bt corn hybrid can be Table 1. Potential economic profit (loss) of is a function of many genes. All hybrids are compared with the potential benefits from Bt corn based upon expected yield, expected not created equally. The insertion of a Bt planting that hybrid, estimated with the control, and five densities of European corn gene into a corn plant should make it a bet- equation: borers ter hybrid but not necessarily the best yield- ing hybrid. The Bt gene provides yield pro- B = (YVLDK) - FBI Expected Corn % Profit tection, not a yield increase. Some non-Bt yield, borersl control (loss)1 hybrids produce yields superior to certain where B = economic benefir in dollars per bu/acre plant acre Bt hybrids. Ideally, in the absence of Euro- acre, Y = expected yield in bushels per acre, 125 0 98 ($10.00) pean corn borers, a near isogenic non-Bt hy- V = market value of corn per bushel, L = 125 0 86 ($10.00) brid should yield the same as a genetically predicted number of larvae per plant, D = 150 0 98 ($10.00) similar Bt hybrid. damage as a proportion yield loss per larva, 150 0 86 ($10.00) Marketing Restrictions. Public percep- K = proportion of larvae killed, and FBI = Bt 175 0 98 ($10.00) tion regarding the safety of transgenic crops technology fee or premium price per acre. 175 0 86 ($10.00) may cause local operators of grain elevators Several scenarios using this equation are 125 0.5 98 ($2.34) to refuse Bt corn. Likewise, some importing presented in Table 1. Note that control of 125 0.5 86 ($3.28) countries may refuse grain delivery or plant- lower densities of European corn borers 150 0.5 98 ($0.81) Downloaded from https://academic.oup.com/ae/article/44/2/75/2474575 by guest on 27 September 2021 ing of transgenic crops (Balter 1997), there- would result in net economic losses, whereas 150 0.5 86 ($1.94) by limiting potential markets for U. S. com- control of higher populations would pro- 175 0.5 98 $0.72 175 0.5 86 ($0.59) pal1les. vide an economic return on the investment. 125 1 98 $5.2] Resistance of European Corn Borer to Because agronomic and environmental fac- 125 1 86 $3.44 Bt. Although populations of European corn tors could mitigate or exacerbate yield losses ISO 1 98 $8.38 borers resistant to Bt have not been found in caused by European corn borers, Table 1 ISO ] 86 $6.13 Bt corn, entomologists expect resistance to should be used only as a guide. Third, gain 175 1 98 $1l.44 occur eventually. Large-scale plantings of Bt thresholds (Higley and Pedigo 1996) can be 175 1 86 $8.81 corn could lead to resistant populations, re- calculated to determine the yield loss neces- 125 1.5 98 $12.97 sulting in the loss of Bt corn as a manage- sary to justify management costs (Table 2). 125 1.5 86 $10.16 ment option. Farmers then would be depen- The gain threshold is calculated: ISO 1.5 98 $17.56 $14.19 dent on chemical methods to manage 150 1.5 86 175 1.5 98 $22.16 economically damaging populations of corn G=C/v 175 1.5 86 $18.22 borers, or they would revert to ignoring the 125 2 98 $20.63 insect and suffering yield losses. where G = gain threshold expressed as 125 2 86 $16.88 Perceived Environmental Risks. Per- bushels per acre, C = cost of management in 150 2 98 $26.75 ceived hazards to wildlife or environmental dollars per acre, and V = market value in ISO 2 86 $17.95 quality may limit use of Bt corn by farmers. dollars per bushel. 175 2 98 $32.88 Such an example is the concern that "drug- 175 2 86 $27.63 producing plants could poison birds feed- Role of the Extension Entomologist ing in corn fields" (Rissler and Mellon Profit (loss) determined using B = (YVLDK) - 1996). However, the reality of this state- Transgenic Bt corn will change dramati- For; see text for discussion. Assumptions: corn market value is $2.50/bushel, Bt corn costs an ment seems grossly unfounded based upon cally the way many farmers manage Euro- extra $10 per acre, each European corn borer the EPA's assessment of the lack of effects on pean corn borers. A few farmers will contin- reduces yields by 5%, events MON810 and nontarget organisms (Environmental Pro- ue to scout their non-Bt corn acres and Btll provide 98% control, event 176 provides tection Agency 1995). apply an insecticide only when necessary, a 86% control. pest management tactic that has proven to Farmer's Dilemma be successful but not widely adopted by pand as transgenic corn hybrids with resis- most farmers. For many, we anticipate that tance to other pests, particularly corn root- The decision to buy Bt corn is not an in- the burdensome complexity of field scout- worms, Diabrotica spp., enter the market- expensive one. If the density of European ing, calculations of economic thresholds, place. Presently, many farmers rightly corn borers exceeds the economic thresh- and anxiety associated with the hazards of question the potential benefits and limita- old, then planting Bt corn will seem like a insecticide use for European corn borer con- tions of Bt corn and the need to manage the wise pest-management decision. The oppo- trol will be replaced by the novel simplicity European corn borer. We, as extension en- site also is true. The dilemma is that popula- of planting seed of Bt corn. We believe that tomologists, have a tremendous opportuni- tion densities of European corn borers are Bt corn is an extremely valuable pest man- ty and responsibility to help them answer unpredictable. Three criteria could be used agement tool that complements other man- their most basic questions about crop man- by farmers to reduce the risk of this unpre- agement tactics. However, we advocate its agement and protection. dictability: historical yield losses caused by use only when farmers are willing to accept European corn borers, estimated cost/bene- stewardship of the technology and follow a Acknowledgments fit analyses, and gain thresholds. scientifically based resistance management First, historical yield loss data from Iowa strategy. The constructive comments of John strongly suggest that European corn borers Extension entomologists can serve a Obrycki, Larry Pedigo, and two anony- potentially cause economic loss annually. valuable role by working with research and mous reviewers are greatly appreciated. Similar losses, however, may not occur with industry entomologists to provide relevant, Thanks to Ken Ostlie for sharing data from equal frequency in other states. Second, the applied, and educational information about his Minnesota Bt corn experiments and Tra- premium or technology fee added to the this technology to farmers. Our role will ex- cy Cameron for providing insecticide cost

AMERICAN ENTOMOLOGIST • Slimmer 1998 77 Table 2. Gain thresholds for different Bt son, N. Desai, M. Hill, S. Kadwell, K. Lau- hybrid technology fees at two corn market val- nis, K. Lewis, D. Maddox, K. McPherson, Marlin E. Rice is professor of entomolo- ues M. R. Meghji, E. Merlin, R. Rhodes, G. W. gy at Iowa State University. He has exten- Warren, M. Wright, and S. V. Evola. 1993. sion and research responsibilities for Technology Market Gain Field performance of elite transgenic insect pests in field crops. Clinton D. fee, $/acre value, threshold, plants expressing an insecticidal protein de- Pilcher is a graduate research/extension $/bu bu/acre rived from . Bio/Tech- assistant in the Department of Entomology nol. 11: 194-200. at Iowa State University. He is working on 2.50 2.0 Mason, C. E., M. E. Rice, D. D. Calvin, J. W. 5.00 pest management questions regarding 5.00 3.00 1.7 Van Duyn, W. B. Showers, W. D. Hutchison, transgenic corn products. 7.50 2.50 3.0 J. F. Witkowski, R. A. Higgins, D. W. On- 7.50 3.00 2.5 stad, and G. P. Dively. 1996. European corn 10.00 2.50 4.0 borer ecology and management. North Cen- 10.00 3.00 3.3 tral Regional Extension Publ. No. 327, Iowa 12.50 2.50 5.0 Stare University, Ames. 12.50 3.00 4.2 Munkvold, G. P. 1998. Disease control in Bt 15.00 2.50 6.0 corn? Integrated Crop Management IC-480 15.00 3.00 5.0 1: 1-2. Iowa State University Extension, Ames. Downloaded from https://academic.oup.com/ae/article/44/2/75/2474575 by guest on 27 September 2021 Gain thresholds determined using G = C/V; Munkvold, G. P., R. L. Hellmich, and W. B. see text for discussion. Showers. 1997. Reduced Fusarium ear ror and symptomless infection in kernels of information. This is journal paper no. J- maize genetically engineered for European 17438 of the Iowa Experiment corn borer resistance. Phytopathology 87: Station, Ames, Iowa. Project No. 3025. 1071-1077. Ostlie, K. R., Hutchison, W. D., and R. L. Hell- References Cited mich [eds.]. 1997. Bt-corn & European corn borer: Long-term success through resistance Balter, M. 1997. Transgenic corn ban sparks a management. N. Central Regional Exten- furor. Science 275: 1063. sion Publ. NCR 602, Univ. of Minnesota, St. Bode, W. M., and D. D. Calvin. 1990. Yield-loss Pau!. relationships and economic injury levels for Pilcher, C. D., J.j. Obrycki, M. E. Rice, and L. European corn borer (Lepidoptera: Pyral- C. Lewis. 1997. Preimaginal development, idae) populations infesting Pennsylvania survival, and field abundance of insect pred- LANIUS Software Presents field corn. J. Econ. Entomo!. 83: 1595-1603. ators on transgenic Bacillus thuringiensis Buschman, L., P. Sloderbeck, Y. Guo, R. Hig- corn. Environ. Entomol. 26: 446-454. Clubtail™ 1.0 gins, and M. Witt. 1997a. Evaluation of Pilcher, C. D., M. E. Rice, j. J. Obrycki, and L. The Dragonfly Database for C. Lewis. 1997. Field and laboratory evalu- corn borer resistance and grain yield for Bt the Serious Odonatist! and non-Bt corn hybrids at Garden City, KS, ations of transgenic Bacillus thuringiensis 1997. 1997 Garden City Bt Corn Trial re- corn on secondary Lepidopteran pests (Lep- If you study dragonflies and damselflies, you have no port, Department of Entomology, Kansas idoptera: Noctuidae). J. Econ. Entomol. 90: 669-678. doubt accumulated a lot of data over the years. Now, State University, Manhattan. there is good news for you! LANIUS Software has Rice, M. E. 1994a. Aerial application of insecti- Buschman, L., P. Sloderbeck, Y. Guo, and V. developed a database application that will provide a Martin. 1997b. Evaluation of corn borer re- cides for control of second-generation Euro- unique solution to your data management problems. sistance and grain yield for Bt and non-Bt pean corn borer, 1991. Mgt. Tests CLOOTAlL 1.0 manages survey and census data corn hybrids at St. john, KS, 1997. 1997 St. 19: 204-205. 1994b. Second-generation European corn bor- related to dragonflies. It features over 60 powerful john Bt Corn Trial report, Department of reporting options. You can use the database to: Entomology, Kansas State University, Man- er control with aerial application of insecti- hattan. cides, 1992. Arthropod Mgt. Tests 19: 205- 1) Maintain specific information on each census you Echtenkamp, J., J. Witkowski, and K. Jarvi. 206. conduct, to include details on the date time location observers, and weather for each censu~that'is entered' 1997. Annual report of field studies. Univer- 1994c. Aerial application of insecticides for 2) Maintain lists of all dragonfly species that are found second-generation European corn borer con- sity of Nebraska, Haskell Agricultural Lab- on each census, to include the state and county in oratory, Concord. trol, 1993. Arthropod Mgt. Tests 19: 206. which each observation was made and the number of Environmental Protection Agency. 1995. Pesti- 1997. Evaluation of Bt corn hybrids for control individuals observed and/or collected· and cide fact sheet. Name of chemical(s}: Baci/- of European corn borer in Iowa field corn, 3) Maintain detailed data, at a variety'of scales, on the specific sites at which odonate surveys are conducted. Ius thuringiensis CrylA(b} d-endotoxin and 1997. Report of Product Evaluation #235- 97, Department of Entomology, Iowa State the genetic material necessary for its produc- CLOOTAlL 1.0 isjust $99.95 + $5.00 StH (CA tion ( vector pC1B4431) in corn. University, Ames. residents add 8.25% sales tax). Requires Windows 95 USEPA, Office of Prevention, Pesticides and Rice, M. E. and K. R. Ostlie. 1997. European or higher. To order, contact LANIUS Software at Toxic Substances. Washington, DC. corn borer management in field corn: a sur- 1470 Creekside Dr., Suite 23, Walnut Creek, CA 94596. Reach us by phone at (510) 932-4201. Higley, L. G., and L. l~ Pedigo. 1996. The ElL vey of perceptions and practices in Iowa and Minnesota. Prod. Agric. 10: 628-634. concept, pp. 9-21. In L. G. Higley and L. P. J. Please visit LANIUS Software on the web at Pedigo [eds.], Economic thresholds for inte- Rissler, J., and M. Mellon. 1996. The ecological www.glenalpine.comllanius to learn more about grated pest management. University of Ne- risks of engineered crops. The MIT Press, CLOOTAlL 1.0 and the other software solutions that LANIUS Software has developed specifically for braska Press, Lincoln. Cambridge, Mass. natural resource professionals such as yourself] Koziel, M. G., G. L. Beland, C. Bowman, N. B. Carozzi, R. Crenshaw, L. Crossland, J. Daw- •

78 AMERICAN ENTOMOLOGIST • Summer 1998