Location: Integrated Cropping Systems Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1: Determine the biological, ecological, and behavioral basis that underlie insect pest (e.g, corn rootworm) resistance to management tactics (including GM crops), and develop novel crop and pest management technologies that enhance development of insect resistance management (IRM) plans. • Sub-objective 1a. In relation to IRM, determine whether resistance to Cry3Bb1 affects the mating behavior and reproductive biology of western corn rootworm. • Sub-objective 1b. Develop rootworm strains resistant to additional Bt corn events and assess trajectory of resistance development and its implications for rootworm fitness. Objective 2: Develop non-chemical tools (e.g., host-plant resistance and biological control) for managing corn rootworms and other insect pests, and devise effective approaches to integrate them into corn production systems. • Sub-objective 2a. Advance germplasm with resistance to corn rootworm larval feeding. • Sub-objective 2b. Identify Quantitative Trait Loci (QTL) associated with reduced damage in rootworm-resistant corn lines. • Sub-objective 2c. Assess the feasibility of winter cover crops as a method for increasing biological control of corn rootworms. Objective 3: Develop strategies to integrate non-chemical weed population management into crop rotation systems and identify environmental and physiological factors that limit the effectiveness of key granivores to regulate weed populations. • Sub-objective 3a. Develop a rotation design that reduces weed community density in organic croplands. • Sub-objective 3b. Evaluate contributions of cultural practices and granivory to weed seedling emergence in soybeans. Objective 4: Examine how herbicide tolerant and insect resistant crop varieties affect multitrophic relationships among soybeans (and other crops), insect pests, and natural enemies. • Sub-objective 4a. Identify and characterize soybean germplasm that is resistant to the soybean aphid. • Sub-objective 4b. Determine the implications of glyphosate-tolerant soybeans on biodiversity and its contributions to biological control of soybean aphids.
1b. Approach (from AD-416):
Sustainable pest management ultimately involves applying ecological principles for reducing insect and weed pressure on key crops. Our project couples bottom-up and top-down processes to reduce key pests (corn rootworms, soybean aphids, and weed communities) of Northern Great Plains crops in agronomically feasible ways that mimic those that regulate pest species within natural habitats. In corn, we will identify lines with natural resistance to rootworms, and will find quantitative trait loci to facilitate their use by seed companies. We also will incorporate winter cover crops into corn production systems in ways that encourage endemic predator communities and increase their impact on rootworms. Fitness-related traits that influence the evolution of rootworm resistance to Bt corn will be identified, and this information will be incorporated into insect resistance management decision-making tools in order to preserve this pest management technology. In soybean, we will discover new soybean lines that express resistance to a key pest, the soybean aphid. Simultaneously, we will determine how to manage non-crop vegetation within soybean fields to promote aphid natural enemies. Weeds are well adapted to current crop rotations, and our research will optimize crop rotations using population-centered approaches that break the weed cycle and increase the impact of insect granivores on weed seedbanks, especially within organic systems. The simultaneous development of top-down and bottom-up mechanisms for pest management are incorporated into sustainable and integrated pest management systems to provide producers with profitable pest management solutions that can be realistically implemented on their farms.
3. Progress Report:
Specific research conducted in FY13 advanced research on the use of bottom-up and top-down processes to reduce key pests (corn rootworms, soybean aphids, and weed communities) of Northern Great Plains crops in agronomically feasible ways that mimic those that regulate pest species within natural habitats. 1a1. All of the resistant and susceptible western corn rootworm matings for this study have been completed. All data on longevity, fecundity, and viable egg production is being analyzed with collaborators. A critical vacancy has delayed progress on this objective. 1a2. Almost all mate competition bouts have been established with Cry3Bb1 resistant and susceptible western corn rootworm males and females. Many of these events were recorded and we are collecting eggs from mated females. A critical vacancy has delayed progress on this objective. 1b. We have continued to expose western corn rootworm neonate larvae to SmartStax and a closely related non-transgenic hybrid and have seen some survivors. Because we could not get non-transgenic seeds without insecticidal seed treatment, we used another untreated variety as suggested by collaborator. We will continue exposing the larvae for several more generations and then begin looking for any fitness related costs associated with resistance. We also collected adults emerging from SmartStax corn as an added field component to selecting for resistance to SmartStax. We will continue to collect and rear corn rootworms emerging from the SmartStax field. 2a&b. The corn/soybean breeder involved in selecting lines for host-plant resistance left for another position, leaving a critical vacancy. 2c1. Because of difficulties in obtaining corn seed not treated with neonicotinoid insecticides, the focus of this project shifted slightly. We examined how increasing predator community structure in 16 corn fields (conducted over two seasons) affected predation intensity on corn rootworm immatures. The paper was submitted. 2c2. We examined how cover crops affect corn root structure, and established cover crops that will precede next year’s corn crop. 3a. Field trials in the 9-year rotation were established. Weed populations and crop characteristics and yield were recorded. Everything is moving forward according to plan. 3b. Field trials in the rotation were established. Ground dwelling insect communities were collected. Seed marking/gut analysis technology was validated and the manuscript published. Marked seeds were placed in the field and a test that detects the presence of the marker (ELISA) were conducted on field-collected predator stomachs. 4a. New soybean lines continue to be evaluated for soybean aphid resistant germplasm. A total of 350 soybean lines and 12 wild soybean lines were planted in field plots near Brookings in 2012 to screen for aphid resistance. However, aphid levels were very low in the plots, even despite supplemental infestation from colony-reared aphids, and meaningful evaluation of resistance was not possible. The 350 soybean lines and six of the 12 wild soybean lines were planted again in 2013 in field plots near Brookings. Natural infestations of soybean aphids were present in the plots a