2010 Annual Report
Multiple mating by female corn rootworms affects their evolution of resistance to Bt corn. Multiple mating in female insects provides genetic variation to their offspring, which enhance their survival and reproduction in changing environments. An important pest of corn, female corn rootworms are believed to mate only once in their lifetime, and this is important to consider when designing non-Bt refuge size and location that a farmer should plant within their Bt cornfields. It is assumed that Bt resistant female corn rootworms mate only once with Bt susceptible males from the refuge and consequently all offspring are Bt susceptible. However, ARS researchers in Brookings, SD showed that many female northern corn rootworms mated two or three times in their lifetime. Thus, if Bt resistant females mate with Bt resistant males, their offspring likely will survive subsequent Bt corn exposure and reduce the efficacy of the Bt corn. Seed companies and regulatory agencies use this information to determine size and location of refuge areas that farmers need to plant on their fields.
The secret sweet-tooth of lady beetles. Lady beetles are best appreciated for their ability to consume crop pests, but they also eat other foods like sugar. Although laboratory studies have shown that sugar-feeding improves lady beetle health, it is unknown how often lady beetles actually eat sugar under natural conditions. Scientists from USDA-ARS in South Dakota and Maryland and from the University of Kentucky collected lady beetles from soybean fields, dissected their stomachs, and examined them for the presence of fructose, a sugar produced by plants. They found that up to 60% of specimens had consumed sugar within the hour preceding collection, indicating that sugar is frequently consumed by lady beetles. This knowledge may be useful to producers as a way to conserve lady beetles (and likely other natural enemies of pests) within the landscape by providing additional sugar sources in and near cropland.
Insecticidal seed treatments on soybean may hurt producers more than they help. Soybean seed is widely treated with systemic insecticides to combat early season pests, but pests in South Dakota typically don’t establish until later in the season. ARS researchers in Brookings, SD tested whether there were any yield benefits to insecticidal seed treatments in eastern SD. An aphid bioassay revealed that all bioactivity of the insecticide was gone after June 24, and that soybean aphids (the dominant pest in our region) did not become established until July. Aphids in both treated and untreated soybeans reached economic injury levels on the same date, and yields were not improved by the treatment. Natural enemies of soybean aphid were less abundant in the insecticide-treated fields. Given no yield benefit, and the adverse effects of the seed treatment on aphid natural enemies, we have determined that insecticidal seed treatments are not profitable for producers of our region.
Biodiversity baseline established for Iowa lady beetles. Lady beetles are generally considered beneficial as major predators of agricultural insect pests. However, recent declines in some native lady beetles and increasing abundance of non-native species have prompted calls for a better understanding of the biodiversity of lady beetles across the United States. An updated and annotated checklist of 81 species of lady beetles for Iowa was developed by ARS researchers in Brookings, SD. The list includes new state records for six species, including one non-native plant-feeding species, and new county records for the invasive multicolored Asian lady beetle. The study identified the need for new records of lady beetles in the state, especially for the twospotted, transverse and ninespotted lady beetles, which were once common and widespread but have declined drastically over much of North America, including Iowa. The information will aid pest-management practitioners and insect conservationists in Iowa to know what lady beetles are present, and it will also establish a baseline of species for developing biodiversity inventories.
Whereabouts of previously common native lady beetles discovered in western South Dakota and western Nebraska. The twospotted, transverse, and ninespotted lady beetles were previously common throughout much of North America, but their numbers have declined drastically over the last few decades. Very few had been found in states like South Dakota or Nebraska in the last 20 years. This trend is troubling because lady beetles are beneficial as predators of agricultural insect pests. However, these three lady beetles were found at nine sites in western South Dakota and western Nebraska in 2008. Nine twospotted, 11 transverse, and 12 ninespotted lady beetles were among 930 lady beetles sampled overall by ARS researchers in Brookings, SD. Also in this study, the seven-spotted lady beetle, a non-native species, was observed feeding upon two kinds of native aphids, providing additional records of predation by this lady beetle on non-target native prey. The results give insect conservationists clues about the types of habitats in which previously common lady beetles may be found, and they identify a specific region of North America in which future research and conservation efforts may be focused.
Preceding crop affects soybean tolerance to weed interference. ARS Researchers in Brookings, SD found that soybean was two-fold more tolerant of a uniform weed infestation when following corn than following spring wheat, oat, dry pea, or soybean. They speculate that soybean tolerance to weeds increases because corn improves resource-use-efficiency of soybean, thus minimizing impact of weed competition for resources. Crop diversity and rotation design helps weed management by disrupting population growth of weeds and reducing weed community density across time. Crop sequences that improve tolerance to weed interference will further reduce the impact of weeds on crop yield. These sequences will be especially helpful in production systems that seek to reduce herbicide use and accept a low density of weeds present in the crop. Our research has identified three sequences that improve crop tolerance to weeds: dry pea preceding winter wheat, dry pea preceding corn, and corn preceding soybean. This change in tolerance to weeds appears to be crop-to-crop specific; only a few sequences improve tolerance to weeds. A further benefit of synergistic sequences is that crop yield is also higher in weed-free conditions.
Anderson, R.L. 2010. A 2-Year Small Grain Interval Reduces Need for Herbicides in No-Till Soybean. Weed Technology. 23:398-403.
Anderson, R.L. 2010. Impact of Preceding Crop and Cultural Practices on Rye Growth in Winter Wheat. Weed Technology. 23:564-568.
Anderson, R.L. 2009. Crop Synergism can Improve Tolerance to Weeds. Quarantine and Protection of Plants. 13:486-491.
El Khisen, A.A., M.O. Bohn, D.A. Prischmann-Voldseth, K.E. Dashiell, B.W. French and B.E. Hibbard. 2009. Native Resistance to Western Corn Rootworm (Coleoptera: Chrysomelidae) Larval Feeding: Characterization and Mechanisms. Journal of Economic Entomology. 102(6): 2350-2359.
French, B.W., Hammack, L. 2010. Reproductive Traits of Northern Corn Rootworm (Coleoptera: Chrysomelidae) in Relation to Female and Male Body Size. Annals of the Entomological Society of America. 103(4):688-694. DOI 10.1603/AN09174.
Hesler, L.S., Kieckhefer, R.W., Mesman, A., Catangui, M.A. 2010. Coccinellidae (Coleoptera) of South Dakota: New State Record for Anatis lecontei Casey and Erratum to Delete Hyperaspis fimbriolata Melsheimer. Coleopterists Bulletin. 64:84.
Hesler, L.S. 2009. An Annotated Checklist of the Lady Beetles (Coleoptera: Coccinellidae) of Iowa, USA. Insecta Mundi 0091:1-10. Available: http://centerforsystematicentomology.org/insectamundi/0091Hesler.pdf.
Hesler, L.S., Losey, J.E., Catangui, M.A., Helbig, J.B., Mesman, A. 2009. Recent Records of Adalia Bipunctata (L.), Coccinella Transversoguttata Richardsoni Brown and, Coccinella Novemnotata Herbst (Coleoptera: Coccinellidae) from South Dakota and Nebraska. The Coleopterists Bulletin 63(4):475-484.
Lundgren, J.G., Lehman, R.M. 2010. Bacterial Gut Symbionts Contribute to Seed Digestion in an Omnivorous Beetle. PLoS One. 5(5):e10831.doi:10.1371/journal.pone.0010831.
Lundgren, J.G., Weber, D.C. 2010. Changes in Digestive Rate of a Predatory Beetle over Its Larval Stage: Its Implications for Dietary Breadth. Journal of Insect Physiology. 56:431-437.
Lundgren, J.G., Toepfer, S., Haye, T., Kuhlmann, U. 2010. Hemolymph Defense against an Invasive Herbivore: Its Breadth of Effectiveness Against Predators. Journal of Applied Entomology. 134:439-448.
Lundgren, J.G. 2009. Nutritional Aspects of Non-Prey Foods in the Life Histories of Predaceous Coccinellidae. Biological Control. 51(2):294-305.
Lundgren, J.G., Ellsbury, M.M., Prischmann, D.A. 2009. Analysis of the Predator Community of a Subterranean Herbivorous Insect Based on Polymerase Chain Reaction. Ecological Applications. 19(8):2157-2166.
Lundgren, J.G., Gassmann, A., Bernal, J., Duan, J.J., Ruberson, J. 2009. Ecological Compatibility of GM Crops and Biological Control. Crop Protection. 28(12):1017-1030.
Lundgren, J.G., Haye, T., Toepfer, S., Kuhlmann, U. 2009. A Multifaceted Hemolymph Defense Against Predation in Diabrotica virgifera virgifera Larvae. Biocontrol Science and Technology. 19(8):871-880.
Pilorget, L., Buckner, J.S., Lundgren, J.G. 2009. Sterol-limitation in a Pollen-fed Omnivorous Lady Beetle (Coleoptera: Coccinellidae). Journal of Insect Physiology. 56:81-87.
Sayed, A., Wiechman, B., Struewing, I., Smith, M., French, B.W., Nielson, C.N., Bagley, M. 2010. Isolation of Transcripts from Diabrotica Virgifera Virgifera LeConte Responsive to the Bacillus Thuringiensis Toxin Cry3Bb1. Insect Molecular Biology. 19(3):381-389.
Weber, D., and Lundgren, J. 2009. Assessing the trophic ecology of the coccinellidae: their roles as predators and as prey. Biological Control. 51: 199-214. http://dx.doi.org/10.1016/j.biocontrol.2009.05.013.