Over 80 million acres of field corn (Zea mays) and 600,000 acres of sweet corn, worth about $65 billion and $1 billion respectively, are grown in the U.S. each year. The European corn borer (ECB) (Ostrinia nubilalis) and western corn rootworm (WCR) (Diabrotica virgifera virgifera) account for over $1 billion each in control costs and grain losses annually. Rootworms are particularly problematic because of their propensity to evolve resistance to management tactics, including crop rotation (Gray et al. 2009), insecticides (Meinke et al. 1998), and now Bt toxins (Gassmann et al. 2011, 2014).


There are numerous other corn insect pests that cause significant economic loss to U.S. corn producers. The southwestern corn borer (Diatraea grandiosella) causes several million dollars in damage to corn in the Western High Plains (Morrison et al. 1977). Recently, the sugarcane borer (D. saccharalis) has emerged as an important corn pest in the south (Castro et al. 2004, Porter et al. 2005). Significant foliage and ear feeders include the two most important lepidopteran pests of corn in the southeast, corn earworm (Helicoverpa zea) and fall armyworm (Spodoptera frugiperda) (Buntin et al. 2004). Losses attributed to corn earworm in sweet corn can be as high as 50% (Wiseman 1999). The western bean cutworm (Striacosta albicosta) has recently expanded its range to become an increasingly serious corn pest as far east as Pennsylvania and north into Canada (e.g. Michel et al. 2010). Among underground pests, the northern corn rootworm (NCR) (D. barberi) is a perennial pest in much of the Corn Belt, and the southern corn rootworm (D. undecimpunctata howardi) is occasionally important, especially in the southeast. Many secondary pests, such as wireworms (Elateridae) and white grubs (Scarabaeidae), can cause serious local problems, and may be resurging with the decrease in soil insecticides used to manage rootworms following wide adoption of transgenic Bt corn. Widespread prophylactic use of neonicotinoid seed treatments to control these secondary soil pests may not be sustainable because of increasing environmental concerns (Mullin et al. 2005, Krupke et al. 2012).


Established in 1953 to address ECB, earlier versions of NC-205 evolved to include a broader array of corn pests. First other stalk-boring Lepidoptera were included, and then other above-ground Lepidoptera. This was a natural progression for the committee, as 1) these pests increased in economic importance, and 2) a pest species does not exist in isolation, but as part of a pest complex and arthropod community. NCCC-46, the Multistate Research Coordinating Committee ‘Development, Optimization and Delivery of Management Strategies for Corn Rootworms’, originated in 1964 as WCR was spreading eastward from the Great Plains into the Central Corn Belt (Gray et al. 2009). NCR was already an economic pest in the Corn Belt, but it was becoming clear that WCR was an even bigger threat to corn production.


During the 1990s, NC-205 and NCCC-46 began to co-locate and meet sequentially during the same week. This was in part because several members were on both committees, but more importantly to invite Industry for discussing the deployment, efficacy, non-target effects, and insect resistance management (IRM) implications of transgenic Bt corn, topics of broad interest to both committees. This sequential meeting model became even more valuable upon the introduction of Bt transgenic corn targeting corn rootworm in 2003, its rapid adoption (Rice 2004), the stacking of genes targeting both corn rootworm and corn Lepidoptera in the same plant, and the discovery of WCR field resistance to Cry3Bb1 toxin (Gassmann et al. 2011). Because of the increasing interaction of NC205 and NCCC46, merging of the committees was discussed during the 2014 annual committee meetings. It was felt that a formal merging of the committees would be of mutual benefit, both scientifically and logistically, and after additional discussion, each committee voted to merge. Therefore, this NC-205 renewal proposal reflects the decision to merge the committee membership and address the larger corn insect pest complex, with emphasis on above-ground Lepidoptera pests and below-ground Coleoptera pests.


Since the commercial release of Bt transgenic corn against ECB in 1996 and against rootworms in 2004, a revolution in corn insect pest management has occurred. Seed companies continue to develop genetically-modified (GM) crops for pest protection. New GM corn hybrids have resistance to a broader range of lepidopteran pests, some have resistance to coleopteran pests, and most current GM hybrids have genes targeting both Lepidoptera and Coleoptera. This technology often eliminates the need to store and handle insecticides and it increases the efficiency of grower operations and pest control (Rice 2004, Sappington 2014). However, the development of resistance by WCR to some Bt toxins is threatening to reverse these gains. Keeping abreast of these changes with timely and relevant research over an area as large and diverse as the U.S. Corn Belt lends itself to a coordinated, committee approach.


Bt corn acreage in the U.S. has increased from 8% in 1997 to 80% in 2014. At this level of adoption, the potential for resistance increases. Research conducted by this committee was used to develop models predicting the rates of resistance evolution and efficacy of refuge in preventing resistance. This led to the IRM approach that used a 20% independent refuge planting; however, as GM technology has evolved, so has IRM. Recently deployed GM corn hybrids use multiple genes that target ECB and WCR. The IRM plan for these hybrids requires a smaller refuge, and seed mixtures (Bt and non-BT) are now being deployed. The models supporting these IRM modifications were constructed using the best information available, but a number of assumptions had to be made. These assumptions must be tested and research conducted to move them from assumptions to quantified variables. Furthermore, information is needed on the economics of this evolving technology at the field, farm, and regional levels. Addressing these knowledge gaps forms the basis for several objectives of the project. The long-term goal of our research is to develop sustainable ways to manage the corn insect pest complex. This is a high regional priority, and in the context of demonstrating sustainable practices, it also is an important national priority.


Relationship between pest control technologies and the agricultural environment. Since 2004 the percentage of U.S. corn acreage with seed-applied neonicotinoids has increased dramatically, and they are now used on virtually all non-organic corn acres. However, across most of the Corn Belt the targeted early-season pest species are sporadic and patchily distributed, and most crop fields do not experience annual economic infestations (Boethel 2012). This begs the questions: “How much protection do neonicotinoid seed treatments offer?” and “What is the risk posed by the most common early season pests in the region?”

Neonicotinoids are attracting attention for their potential role in pollinator declines and possible contamination of surface waters (Goulson 2013, Hladik et al. 2014, van der Sluijs et al. 2014). Seed-applied active ingredient can persist in soil for up to two years and move into aquatic systems where it can simplify aquatic invertebrate communities (Laurent and Rathahao 2003, Krupke et al. 2012, Van Dijk et al. 2013). A recent Canadian study revealed substantial ground water contamination with thiamethoxam (Main et al. 2014). It is clear an evaluation of the effects of seed treatments upon a range of non-target insects in and around cornfields is warranted.


Ecology, evolution, genetics, and behavior of corn arthropods. The WCR and ECB genomes, and the WCR transcriptome, were recently sequenced through international efforts involving several Committee members. Annotating, mining, and maintaining these rich and powerful databases will require an ongoing, collaborative community effort. These genomics gateways will facilitate probing the genetic basis of many important pest traits, including insecticide resistance (Alves et al. 2006), behaviors relevant to pest status, and insect-plant interactions. Furthermore, the potential role of microbial associates on these traits can begin to be assessed. Development of genetic markers and genomics tools by Committee members is allowing more sensitive population genetics studies for estimating dispersal distances of corn insects. Spatial and temporal aspects of adult movement have proven difficult to characterize in both WCR and ECB, despite significant recent advances by Committee members. A comprehensive understanding of mating behavior and dispersal is critical for modeling development and spread of resistance to Bt corn, estimating gene flow, and implementing IRM.


The introduction of Bt transgenic corn hybrids and neonicotinoid seed treatments, have increased the need for addressing critical regional issues largely because the agricultural landscape has changed. Changes in corn rootworm biology, pest management technologies, and regulatory issues over the last several years have illustrated the fact that much of our past information and research about these systems must be re-evaluated. More information is needed on geographic patterns of ECB genetic variation, voltinism, pheromone blend, sensitivity to Bt, and the influence of host plants. Promotion of an IPM-based approach to the deployment of rootworm-Bt products has reached a critical cross-roads, as resistance to some toxins has led to recommendations from various quarters to layer multiple control tactics on Bt corn, including conventional insecticides, without assessing actual need. The Committee has an interest in use of Bt and other insect control tactics in an economically viable and sustainable manner that will prevent or delay the onset of insect resistance. Ensuring long-term durability of these tools requires IRM strategies that are compatible with production practices.


IPM and IRM systems for the corn arthropod complex. Monitoring for resistance among target pests to plant-incorporated insecticidal toxins remains an EPA mandated component of IRM for insect pest-targeting transgenic corn (Siegfried and Spencer, 2012). Being able to detect insecticide resistance is necessary to determine if control failures are because of resistant insects or other factors, determine the extent of the resistance, and design resistance mitigation programs. This is particularly important for WCR which was recently confirmed as resistant to Cry3Bb1 and mCry3A (Gassmann et al. 2011, 2014). There is an urgent need to characterize resistance of rootworms to Cry3Bb1 and other cry toxins and to develop and deliver IPM recommendations to mitigate rootworm resistance. Recently a decline in Cry1F susceptibility of western bean cutworm has been reported (Smith et al. 2014), so a geographic assessment of Cry1F susceptibility is necessary, as well as a proactive plan to address the risk of resistance to Vip3A and other insecticides. As additional pests become primary targets of transgenic technology, monitoring methodologies and programs will have to accommodate these new target pests.


The ear-feeding guild has gained increased attention during the last decade for several reasons, including the range expansion of the western bean cutworm (e.g. Michel et al. 2010), the association between insect feeding and aflatoxin, and the implications of differential kernel feeding for IRM. This complex includes several Lepidoptera, but also coleopteran and hemipteran pests, which presents significant management and research complications. Basic issues such as accurate quantification of injury and the effects of sequential feeding require characterization, as well as the broader issues relating to IPM and IRM.


In 2013 the cotton bollworm (H. armigera), an Old-World pest, was detected in Brazil (Czepak et al. 2013, EMBRAPA 2013, Specht et al. 2013). This was the first report of this pest in the Americas. An insect capable of long distance migration (Pedgley 1985), it presents a significant risk of entering the U.S. Early detection and response plans for this potential corn pest are an immediate need.


Diverse delivery methods for sustainable management of corn arthropod pests. The audience for the results of this project has grown. It comprise farmers and other ag-professionals, but also policymakers, researchers, educators, concerned citizens, and their expectations are greater than ever before. It is critical that results be packaged as unbiased information for these agricultural and public sectors. While traditional information dissemination is still needed, stakeholders are expecting that information be timely, provided in new formats, interactive, and accessible from their home or office.


A comprehensive IPM system is needed for cost-effective prevention, early detection, rapid diagnosis, and mitigation of new and emerging corn pests that links all stakeholders (e.g. myfields.info). We need to transform how we extend information using mobile technologies and web-based social networks. Defining elements needed to sustain user interests in the system is critical; a positive user-experience leads to increased use and rapid integration of stakeholder inputs. Knowledge gaps in specific areas must be addressed in multiple geographic regions to allow uniform application of the system. Using this approach, a blend of smartphone technologies and social networks with traditional Extension activities will lead to rapid detection and cost-effective management of new and common corn pests.


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 technology transfer is appropriate and necessary. Geography plays an important role in how 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. Controversy about the effect of GM and seed treatment 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 these technologies. Answers to questions regarding new technologies should help focus the public's perception of them and allow growers to gain the pest control advantages provided by future technologies.


The proposed multi-state plans will continue to 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, behavior, and evolution. Our work will continue to provide science-based assessments essential to the policy decision-making process, which should help to increase the public's acceptance of environmentally friendly technologies while identifying potential negative impacts that need further investigation. Our work also will continue to lead to more sustainable pest management systems for the corn pest complex. There is ample evidence that the merged NC-205 and NCCC-46 research groups have 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.