S1055: Biology, impact, and management of soybean insect pests in soybean production systems.
Statement of Issues and Justification
Statement of Issue(s) and Justification: Soybean production is increasing to meet the world demand for protein amid dwindling food supplies. Since 2009, the US has produced over 3 billion bushels of soybeans, generating $32 billion in production value (NASS). However, various native and invasive insect pests whose distributions are rapidly expanding and adapting to management practices threaten soybean yield and quality. In the Mid-South, up to 70% of acreage is treated for stink bugs, corn earworm, and other lepidopteran defoliators each year, with the estimated value of yield loss plus management costs of $51.76 per acre. In the Midwest, untreated economic soybean aphid infestations can further reduce production value by 3%, causing an estimated annual loss of $2.4 billion (Tilmon et al. 2011). In the short-term, loss of current highly effective management tactics due to expanding pest complexes is increasing producer costs. In the long-term, the establishment of invasive insect pests will continue to impact soybean ecosystems, including interactions with native pests and the biological control offered by various natural enemies. To address these concerns, coordinated research and Extension delivery are necessary to rapidly understand native and invasive pest biology, develop best management practices, and deliver recommendations to soybean producers.Throughout the history of SDC347, this multi-state project has had an excellent record of rapidly addressing the needs of stakeholders. To further underline our positive relationships with stakeholders, participants are supported by state, regional and national soybean commodity groups as well as industry to develop soybean integrated pest management (IPM) insect research and Extension activities. Native and historical pests of soybean continue to present challenges to producers. Invasive pest problems, such as soybean aphid (a major focus of the group over the last decade), have been and will continue to be effectively addressed by this regional project. Major examples of changing soybean pest issues since the last project renewal include the emergence of new, invasive new Heteropterans (aphids, stink bugs, and Plataspids) and the geographical spread of established species. Coleopterans (Musser et al. 2012) and lepidopterans are developing insecticide resistance and expanding their range of distribution. Indeed, corn earworm (Helicoverpa zea) remained the most important soybean insect pest in Mississippi (Musser et al. 2011a). Specifically, recently introduced pests, such as brown marmorated stink bug, kudzu bug, and redbanded stink bug, pose new challenges to the North American soybean industry (Suiter et al. 2010; Temple et al. 2011; Hebert 2011; Zhang 2012). These pests occur over multiple states presently, and all are expanding their ranges each year. Therefore, coordinated, area-wide research approaches are necessary to understand their biology, develop and deliver management recommendations, and track their distribution to minimize impact on soybean production. This approach has the ancillary benefit of avoiding overlapping research between regions. Specific research objectives include a need to develop and optimize reliable sampling methods, action thresholds, and cost-effective management strategies to maximize sustainable soybean production (e.g. Musser et al 2011b). Without research-based management recommendations, millions of dollars can be lost as a result of decreased yields or seed quality, improper deployment of control recommendations, and/or increased insecticide resistance. SDC347 participants have the skills, facilities and knowledge to develop and implement effective and user-friendly IPM programs for these pests and future insect pest problems. Moreover, they have a recent history of doing this type of work, and details of these achievements follow. Furthermore, as these soybean pests spread to new areas, additional participants benefit from the research performed by other regions. Along with the changing pest complexes, soybean producers are also faced with managing pests with new tools and technologies. Increases in commodity prices and the high-value and demand for food grade and specialty soybeans (i.e., low-linolenic acid) have shifted growers attitudes from IPM to an insurance-based strategy. This shift of management tactics often results in the use of prophylactic treatments to prevent pest damage, usually without any quantification of pest numbers, or even the species present. The majority of soybean seed planted in North America is now treated with insecticides and/or fungicides, with 100% coverage (as is currently the case in corn) anticipated within the next several years at the current rates of implementation by the seed companies. Unnecessary insecticide use has the potential for negative effects on several levels, not the least of which is enhancing the potential for resistance. For example, the use of insecticidal seed treatments has dramatically increased, despite documented (by several members of SDC347) ineffectiveness in controlling late-season pest problems such as soybean aphid (Hodsgon et al. 2012). The insecticides are simply not present in foliage late in season when aphids colonize fields. The insecticides used are highly persistent and toxic to a range of beneficial organisms, with those effects remaining largely undefined at present. Furthermore, in the Southeast, insecticidal seed treatments are increasing in use and are generally targeted toward threecornered alfalfa hopper, bean leaf beetle and thrips. In North Carolina and Virginia insecticidal seed treatments are very efficacious for thrips, the most commonly found seedling pest of soybeans. However, a single yield loss due to thrips has never been recorded (Reisig et al. 2012). Newer methods of pest control are being developed and implemented, including host-plant resistance and transgenic (Bacillus thuringiensis-based) soybean. Varieties with soybean aphid resistance have been commercially released, despite the observation of aphid populations that have overcome the in-plant resistance almost immediately (i.e., virulent biotypes) (Michel et al. 2011; Hill et al. 2010). Research is needed on characterizing virulent biotype adaptation, uncovering novel resistant genes, and developing strategies that sustain the durability of host-plant resistance, including the use of multiple toxins (or stacking of traits) within single varieties. Industries have developed transgenic soybean for lepidopteran control, and these varieties have been evaluated by SDC347 participants. However, unlike the comparatively well-developed refuge strategies in corn, there are no plans or recommendations for maintaining the durability of these transgenic soybean varieties. Given the widespread distribution of soybean aphid and its unrivalled reproductive and migratory capacity (Tilmon et al. 2011), it is an ideal candidate to develop resistance to in-plant toxins. Consequently, strategies to ensure the proper and responsible deployment of these varieties are needed to delay insect resistance.
Advantages of Multi-State Effort. As soybean pests expand and spread across the soybean growing region, multi-state, collaborative research is necessary to discern management tactics that work under different cropping conditions and systems. These activities combine the expertise and efforts of multiple scientists leading to more timely and effective IPM solutions. With soybeans grown in 26 states and provinces and many soybean insect pests distributed across state and provincial borders, SDC347 is a natural working group for addressing soybean pest problems, and it has worked synergistically for years to benefit soybean industries in the US and Canada. Multistate collaborations already exist, and many management tactics have been successfully developed, delivered and implemented including IPM programs for lepidopteran defoliators, three-cornered alfalfa hopper, southern green, green and brown marmorated stink bug, slugs, and soybean aphid (Musser et al. 2011a; Hebert 2011).
SDC347 is composed of experienced basic and applied research and Extension entomologists from all soybean producing states in the US and provinces in Canada. Our working group also includes entomologists from universities and government agencies like the USDA. Participants maintain connections and collaborations through multi-state projects and with various state, regional and national commodity organizations as well as private industry. Through coordination of SDC347, these scientists have an excellent record of developing and implementing effective IPM programs for major insect pests attacking soybeans. In 2009, SDC347 (then named S1039) received the National Excellence in Multistate Research Award from the American Public Land-Grant Universities. Based on these prior accomplishments and our ongoing inertia, we feel strongly that our group is positioned to continue to deliver useful, science-based information to our stakeholders in the face of new and changing pest challenges.
Likely Impacts. SDC347 will generate necessary data on established and invasive soybean pest densities, distributions and biology that are critical to improve overall national soybean IPM programs. Most recently the group focus has been strongly on soybean aphids (Tilmon et al. 2011; Hodsgon et al. 2012). That will continue to be an area of focus, but invasive stink bugs, plataspids and insecticide-resistant Lepidoptera will receive more attention during the next several years (Suiter et al. 2010; Temple 2011; Hebert 2011). In general, the project will continue to focus on maintaining a sustainable soybean IPM program where sustainability is defined as pursuing maximal profitability in the short-term without sacrificing the potential for long-term stability of the system. We will continue our focus on utilizing a combination of biological, cultural, physical, and chemical tools to regulate pest populations while minimizing environmental risks.
Back to Top