Over 80 million acres of field corn (Zea mays) and 600,000 acres of sweet corn, worth about $40 billion and $1 billion respectively, are grown in the U.S. each year. The European corn borer (ECB), Ostrinia nubilalis, accounts for over $1.85 billion in control costs and grain losses annually. In 2006, 88% of the fresh market sweet corn acreage was treated with one or more insecticide applications for a total of 605,000 lbs of insecticides applied. ECB also attacks many other crops, such as sorghum, small grains, potatoes, beans, tomatoes, and peppers. The southwestern corn borer, Diatraea grandiosella, causes about $1 million in damage in the Western High Plains (Morrison et al. 1977). Recently, the sugarcane borer, Diatraea saccharalis, has emerged as an important corn pest in the southern U.S. Other significant stalk-boring pests include the common stalk borer, Papaipema nebris, hop vine borer, Hydraecia immanis, and potato stem borer, Hydraecia micacea.

Since 1950, previous committees have focused on ECB and other stalk-boring lepidopteran corn pests. In addition to stalk borers, we propose to address the other lepidopteran corn pests, which include those that feed on corn leaves and ears. This is a natural progression for the committee, as these pests are increasing in economic importance. Corn earworm, Helicoverpa zea, and fall armyworm, Spodoptera frugiperda, consume corn leaves, tassels, silk and kernels. In the southeastern U.S., losses attributed to corn earworm in field corn range from 1.5-16.7%, and sweet corn losses can be as high as 50% (Wiseman 1999). Black cutworm, Agrotis ipsilon, is the most damaging of the cutworm complex in the Corn Belt. Stand loss over 25% and yield losses of about 2,900 kg/ha are not unusual (Showers et al. 1983, Showers 1999). Western bean cutworm, Striacosta albicosta, increasingly is a pest of corn ears across the north central region.

Since the commercial release of Bacillus thuringiensis (Bt) transgenic corn in 1996, a revolution in corn insect pest management has occurred. This revolution is rapidly moving corn pest management away from synthetic pesticides to plant-based toxin delivery systems. The use of Bt sweet corn varieties has been less dramatic, but is important because of its higher insecticide inputs and direct use as human food. This technology often eliminates the need to store and handle insecticides and it increases the ease of planting and pest control.

Seed companies continue to develop genetically-modified (GM) crops for pest protection. The first GM corn produced was resistant to ECB and a few other lepidopteran pests. New GM corn hybrids have resistance to a broader range of lepidopteran pests, and some have resistance to coleopteran pests. The most current GM hybrids have two genes targeting lepidopteran pests and two genes targeting coleopteran pests. These changes in corn technology have caused major changes in the agricultural community and identified major knowledge gaps, increasing the need to reevaluate knowledge about ECB and other corn pests. For example, an insect resistance management (IRM) program was never a legal requirement for any pest management technology until the introduction of Bt corn. Publicity and attention to scientific advisors led the EPA to require IRM programs on farms where Bt corn hybrids are used; consequently, the concept that resistance could be prevented went from a theory to an experiment in-progress.

Bt corn acreage in the U.S. has increased from 8% in 1997 to 63% in 2009. Corn hybrids that have multiple genes targeting both ECB and corn rootworm could further increase the percentage of acres planted to Bt corn for ECB because in some regions corn rootworm is considered a more important economic pest than ECB. As the level of adoption increases, the potential for resistance evolution increases. Research conducted by this committee was used to develop models predicting the rates of resistance evolution and to investigate the role of refuge in preventing resistance. This led to the IRM approach that utilized a 20% refuge; however, as GM technology has evolved, so has IRM. Recently deployed GM corn hybrids utilize multiple genes that target ECB. The IRM plan for these hybrids requires a smaller refuge of at least 5% (in non-cotton production regions), and seed mixtures (Bt and non-BT) are being considered for future GM corn. The models used to allow for these IRM modifications were constructed using the best information available, but a number of assumptions had to be made. These assumptions need to be tested and research conducted to move them from assumptions to quantified variables. In addition to addressing these information gaps, information is needed on the economics of this evolving technology. Eliminating these information gaps forms the basis for several objectives of the project. The long-term goal of our research is to develop sustainable ways to manage lepidopteran corn pests. This is a high regional priority, and in the context of demonstrating sustainable practices, it also is an important national priority.

Implications of GM corn in the landscape and pest management. Insect pests commonly have developed resistance to conventional insecticides when they are overused (Georghiou 1986), and scientists and growers are concerned that overuse of Bt corn could produce pests resistant to Bt toxins (e.g. Tabashnik 1994, Gould 1998). One of the biggest hindrances to providing accurate assessments of resistance risk is the lack of resistant colonies that are able to survive on transgenic plants. Such colonies would provide the opportunity to validate existing IRM strategies, identify resistance-associated genes, and develop molecular markers that are diagnostic for resistance. Recently, an ECB colony has been selected for that exhibits high levels of resistance to Cry1F and increased ability to survive on Cry1F corn tissues (Alves et al. 2006). Likewise, a colony of sugarcane borer was developed with resistance to Cry1Ab corn (Huang et al. 2009). Research on such colonies can aid in answering questions pertaining to the risk of Bt resistance development, help characterize genetic markers assay of Bt resistance, and help in development of diagnostic assays for resistance. The research can directly assist in the formulation of IRM strategies for GM crops by providing biological data that has previously been unavailable.

Because of the widespread use of Bt corn, there exists the potential for area-wide suppression of ECB populations, and the evidence for this is building (Hellmich 2006, Hutchison et al. 2007, Storer et al. 2008). Assessments of the benefits of Bt corn have usually focused on agronomics directly related to the crop (e.g. Marra and Piggott 2006), but by suppressing ECB populations, there may be far reaching economic, environmental, and human health benefits to not only users of Bt corn, but to non-Bt corn growers and others who grow crops for which ECB is a pest. It is therefore important to quantify the landscape-scale suppression of ECB associated with widespread Bt corn use and to estimate the farm and market level economic, environmental, and health benefits resulting from this suppression.

Another issue has been the need to more fully understand the impacts of GM technologies on non-target organisms. Never before in the history of pest management has there been as much pressure placed on the scientific community by the general public to understand the ecological impacts of new pest management tactics. Although numerous experiments have indicated that toxins produced by Bt corn have few if any significant negative effects on non-target organisms, debate continues in the scientific community (e.g. Romeis et al. 2008, Lovel et al. 2009). Members of this committee have contributed knowledge about the non-target impacts of GM crops, but there is not yet an accepted way of judging how much and to what extent change in biodiversity is important. Research to help understand how ecosystems function, and how new practices are changing the biodiversity in and near cornfields, is needed.

Adaption of IPM systems for changing pest complexes. Since the advent of Bt corn, there has been a shift in the corn pest complex in many regions. For example, the western bean cutworm historically has been a pest of corn in the western Great Plains (Keaster 1999). Since 2000, western bean cutworms have been increasing in abundance east of Nebraska, (ORourke and Hutchinson 2000, DiFonzo and Hammond 2008) and are now found as far east as Ohio (DiFonzo and Hammond 2008). Reasons for the recent range expansion are not known, but several possibilities are proposed, such as increased use of reduced tillage, milder winter temperatures, reduced precipitation, reduced use of foliar insecticides, and suppression of competitors (Catangui and Berg 2006). Yield losses of 30-40% have been reported, and a nominal threshold of 8% of plants infested with egg masses or small larvae has been used in its original range (e.g. Seymour et al. 2004). More comprehensive economic thresholds and management recommendations are needed across its current range, and there is increasing interest in monitoring procedures.

Climate change has important implications for corn IPM. Warmer temperatures and changing precipitation patterns may be in part responsible for the range expansion of western bean cutworm, but also for a host of corn pests. Range expansion of four major corn pests, including corn earworm and ECB, has been predicted by analyzing pest overwintering thresholds and degree-day requirements along with climate change projections (Diffenbaugh et al. 2008). These range expansions could have significant economic impacts via increased yield loss and management costs. Corn IPM will necessarily have to adapt to these changing conditions.

Changes in disease incidence also are expected with changes in pest complex. Corn diseases cause up to 15% yield loss in the U.S. (White and Carson 1999), costing over $3 billion annually. Fungal infection of ears can reduce quality of the grain, but also cause disease in humans and livestock that consume contaminated grain or its products. The FDA has established action levels that regulate concentrations of aflatoxins as low as 20 parts per billion in livestock feed (van Egmond, 1991). Incidence of fungal infection and concentrations of mycotoxins is increased in plants injured by insects. For example, grain produced by plants infested with southwestern corn borer had higher concentrations of aflatoxin than uninfested plants (Windham et al. 1999). Research conducted with Bt transgenic corn and their near-isogenic non-transgenic counterparts indicated a decrease in ear rot severity and mycotoxin concentrations in the Bt corn; however, it is not known if this relationship will hold true for pests that are only partially controlled by current Bt corn hybrids.

Ecology, evolution, genetics, and behavior. ECB is not only a major pest of corn, but is also a model species for lepidopteran genetics (Willet and Harrison 1999, Ferré and Van Rie 2002, Dopman et al. 2005), speciation (Roelofs et al. 1985, Linn et al. 1997, Dopman et al. 2004), insect/host-plant interactions (Ponsard et al. 2004, Calcagno et al. 2007, O'Rourke et al. 2009), and IRM (Ives and Andow 2002, Shelton et al. 2002, Qiao et al. 2008). Clarification of population structure and genetics is necessary to model the risk of resistance development and to design IRM strategies. More information for this species is needed on geographic patterns of genetic variation, voltinism, pheromone blend, sensitivity to Bt, and the influence of host plants to develop models of gene flow. Also, little is known of the population structure and genetics of other corn Lepidoptera. Acquiring such information will increase our understanding of the mechanisms of resistance, genetic basis for resistance, status of cross-resistance, and stability of resistance.

The advent of new DNA sequencing technologies is bringing the potential for genomics research within range of even nonmodel organisms. Genomics research on lepidopteran pests will provide opportunities to probe the genetic basis of many phenomena, including insecticide resistance (Alves et al. 2006), behaviors relevant to pest status, and insect-plant interactions. Construction of EST libraries will facilitate development of genetic markers necessary for population genetics studies and enhance development of linkage maps and QTL mapping for ECB (Coates et al. 2008, Khajuria et al. 2009). The coming explosion of sequence data will require coordinated development and maintenance of genomics databases for data presentation, mining, and annotation.

Despite nearly a century of research on ECB, spatial and temporal aspects of ECB movement and mating behavior have proven difficult to characterize. A clear understanding of mating behavior is important for modeling and estimating the likelihood of resistance developing in ECB to Bt corn (Guse et al. 2002), estimating gene flow, and implementing IRM. Analyses of gene flow indicate a substantial exchange of ECB migrants between locations separated by 1000 km or more (Bourguet et al. 2000, Malausa et al. 2007, Krumm et al. 2008, Kim et al. 2009). Such high gene flow implies that resistance to Bt corn will be slow to develop, but if it does develop, it will rapidly spread. However, it is not clear if these results can be extrapolated outside the Corn Belt. The situation in the eastern U.S. is further complicated by a number of sympatric races of ECB. A better understanding of the behavior and ecology of the races is critical to effective IPM and IRM of ECB.

Enhancing natural control is the first line of protection in IPM. Even though the biology of most of the natural enemies associated with corn has been described, the effects and value of these natural enemies in the landscape is not well understood. Information gaps include understanding patterns of variation in natural enemy communities in a corn and soybean agroecosystems. Gaps extend to quantifying the role of natural enemies in resistance evolution, improving the use of augmentative biological control, and characterizing the economic value of natural enemies (Musser et al. 2006). Scientists studying the impact of Bt crops on natural enemies generally conclude that there is little direct effect from the Bt itself (Marvier et al. 2007, Dhillon and Sharma 2009); however, the dynamics associated with how the change in pest populations in Bt corn affects natural enemies need to be studied.

As previously noted, the western bean cutworm has been expanding its range, and little is known about the causal factors. Two potentially important factors are pathogenic microsporidia that infect it (Su 1976, Dorhout 2007) and its host plants (Blickenstaff and Jolley 1982). Research and population genetics analyses are necessary to investigate the interactions between genetic diversity, range expansion, gene flow, microsporidian infection and host plant usage. Knowledge is needed that will provide a scientific foundation to develop innovative ways to manage this pest. Furthermore, this is a rare opportunity to study a biological invasion as it happens and it will serve as a model for invasive species.

For philosophical or economic reasons, not all growers will adopt Bt corn, and effective management options are needed. For example, little research has been conducted on managing ECB in organic corn (Delate and Cambardella 2004, Evering 1985). Organic corn production has been steadily increasing, which is raising the need to conduct research on basic biology of corn pests in this system.

Electronic delivery of information. The audience for the results of this project is growing. Not only does it comprise farmers and other ag-professionals, but also policymakers, researchers, high school and university educators, concerned citizens, and their expectations are greater than ever before. It is critical that the results be packaged as unbiased information for these agricultural and public sectors. The days of publishing hard copy documents and then simply distributing them or posting them online are over. While traditional information dissemination is still needed, stakeholders are expecting that information be provided in various formats, be timely, immediately accessible from their home or office, interactive, and provide real-time data.

In 2010 an updated edition of this committees publication, NCR-327 European Corn Borer Ecology and Management will be published. An online version could provide a platform for an expanded, interactive version with economic threshold calculators, scouting video clips, links to pest trap networks, and other pertinent publications and educational material. It also could provide the opportunity to obtain important feedback from stakeholders. For example, online surveys could assess growers needs and opinions concerning corn IPM and adoption of IRM practices. This data could then be used to balance logistical and economic expectations for effective corn pest management with the desire to maintain long-term durability of new technologies. As the body of corn Lepidoptera biology, ecology, IPM and IRM knowledge grows in both volume and complexity, it is critical that stakeholders have a complete, easily accessible source of scientifically-based, unbiased information that the NC-205 committee can provide.

A Multi-State Approach. Collectively, a multi-state approach to researching the knowledge gaps described above, developing IPM tools and programs, assessing IRM strategies, and implementing effective technology transfer is appropriate and necessary. As shown above, geography plays an important role in how the pests interact with other organisms in their environment, and how IPM and IRM strategies are designed and employed. It is this significant spatial effect of population and community dynamics that make a regional project necessary. Lack of knowledge has led to fears by the general public about the potential environmental and health risks associated with adoption of new technologies, particularly GM technologies. Controversy about the effect of GM technology on non-target organisms and human health has fueled public concerns. These fears have the potential of forcing legislation to ban or slow the introduction of GM crops. Answers to questions regarding Bt-corn should help focus the public's perception of this technology and where benefits are clearly demonstrated, and allow growers to gain the pest control advantages provided by this and future technologies.

These multi-state plans will be a model for the development of science-based resistance management programs and risk assessment for other pests, other crops, and future crop protection technologies. Our efforts will provide fundamental advances in the knowledge of pest ecology, genetics, and evolution. Our work will continue to provide scientifically-based assessments essential to the policy decision-making process and should help to increase the public's acceptance of these technologies and to identify potential negative impacts that need further investigation. Our work also will continue to lead to more sustainable pest management systems for lepidopteran corn pests. We also view it as our responsibility to provide unbiased, scientifically-based information that fosters subsequent investment in promising novel approaches to pest management. There is ample evidence that the NC-205 research group has the skills, collaborative working relationships, and commitment to provide the missing biological information and to incorporate this new information into evolving IPM programs and IRM models.