Showing papers by "Erin W. Hodgson published in 2017"

Evidence for Soybean Aphid (Hemiptera: Aphididae) Resistance to Pyrethroid Insecticides in the Upper Midwestern United States.

Abstract: Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a damaging invasive pest of soybean in the upper Midwest. Threshold-based insecticide applications are the primary control method for soybean aphid, but few insecticide groups are available (i.e., pyrethroids, organophosphates, and neonicotinoids). To quantify current levels of soybean aphid susceptibility to pyrethroids in the upper Midwest and monitor for insecticide resistance, leaf-dip bioassays were performed with λ-cyhalothrin in 2013-2015, and glass-vial bioassays were performed with λ-cyhalothrin and bifenthrin in 2015 and 2016. Soybean aphids were collected from 27 population-years in Minnesota and northern Iowa, and were compared with a susceptible laboratory colony with no known insecticide exposure since discovery of soybean aphid in North America in 2000. Field-collected aphids from some locations in leaf-dip and glass-vial bioassays had significantly lower rates of insecticide-induced mortality compared with the laboratory population, although field population susceptibility varied by year. In response to sublethal concentrations of λ-cyhalothrin, adult aphids from some locations required higher concentrations of insecticide to reduce nymph production compared with the laboratory population. The most resistant field population demonstrated 39-fold decreased mortality compared with the laboratory population. The resistance documented in this study, although relatively low for most field populations, indicates that there has been repeated selection pressure for pyrethroid resistance in some soybean aphid populations. Integrated pest management and insecticide resistance management should be practiced to slow further development of soybean aphid resistance to pyrethroids.

Determining the Effectiveness of Three-Gene Pyramids Against Aphis glycines (Hemiptera: Aphididae) Biotypes

Abstract: Since the discovery of Aphis glycines Matsumura (Hemiptera: Aphididae) in the United States, the primary management tactic has been foliar insecticides. Alternative management options such as host plant resistance to A. glycines have been developed and their effectiveness proved. However, the use of host plant resistance was complicated by the discovery of multiple, virulent biotypes of A. glycines in the United States that are capable of overcoming single Rag genes, Rag1 and Rag2, as well as a two-gene pyramid of Rag1+Rag2. However, current models predict that the virulent allele frequency of A. glycines decreases in response to the use of pyramided Rag genes, suggesting that pyramids represent a more sustainable use of these traits. Previous research has demonstrated that virulent biotypes can be effectively managed using a three-gene pyramid of Rag1+Rag2+Rag3. Additional Rag-genes have been discovered (Rag4 and Rag5), but whether the incorporation of these genes into novel three-gene pyramids will improve efficacy is not known. We tested single-gene (Rag1 and Rag2) and pyramid cultivars (Rag1+Rag2, Rag1+Rag2+Rag3, Rag1+Rag2+Rag4) to multiple biotypes in laboratory assays. Our results confirm that the Rag1+Rag2+Rag3 pyramid effectively manages all known A. glycines biotypes when compared with cultivars that are overcome by the associated biotype. Our results indicate that Rag1+Rag2+Rag4 would be an effective management option for biotype-1, biotype-2, and biotype-3 A. glycines, but had a negligible impact on biotype-4.

Farmers perspectives on resistance in western corn rootworm to CRW-Bt corn in Midwest USA

Abstract: Resistance in western corn rootworm to transgenic corn hybrids was first confirmed in 2011 in Midwestern USA, and threatens their continued use. Farmers are often the first line of resistance detection, so their understanding and attitudes toward this issue are critical for improving resistance management. We conducted telephone focus groups during 2013 with farmers who had experienced rootworm resistance. There were four stages in dealing with unexpected rootworm injury: Awareness of a problem, diagnosis, confirmation, and recommendations. Most farmers discovered the problem themselves, but this usually happened too late in the growing season to limit yield loss. Once aware of a problem, farmers first sought help diagnosing the problem from their seed dealer, chemical rep, and/or crop consultant. They considered the problem to be a significant one, both because of its severity and suddenness, and were concerned about their difficulty in obtaining a correct diagnosis. They eventually used extension entomology specialists to confirm the diagnosis. Farmers gathered recommendations from independent consultants, input suppliers, and extension and indicated that they would aggressively deal with the problem, because they were not sure of what would work to protect their crop. They recommended that public extension put more emphasis on increasing awareness of the problem, assessing the extent of the problem and being an unbiased source of information. However, farmers were unlikely to report rootworm injury if the perceived barriers to reporting outweighed the perceived incentives. These barriers were emotional ones, including being unsure who to trust, fear that reporting will be time-consuming, and shame that they did something wrong. The incentive was access to credible advice. They did not automatically acknowledge the broader social benefits of reporting. Thus, extension probably needs to be explicit about these broader benefits to obtain information about the extent of the problem. With the conflicting demands and multiple information sources, it will be a challenge for extension to involve farmers to improve resistance monitoring and management. Key words: Resistance management, focus group, qualitative analysis, Diabrotica virgifera, genetically modified organism, transgenic crop, extension.

Ecology and management of European corn borer in Iowa field corn

Abstract: This publication discusses the European corn borer life cycle, injury to corn, and management options with a focus on Iowa field corn production. European corn borer, Ostrinia nubilalis (Figs. 1–2), is a moth in the family Crambidae (formerly Pyralidae). European corn borers in the Midwest affect corn production (i.e., field corn, popcorn, seed corn, and sweet corn), as well as sorghum, wheat, and many vegetables. Caterpillars can feed on almost any part of the corn plant, except roots, and cause severe economic injury (Fig. 3).

Soybean Aphid Efficacy Screening Program, 2016

Abstract: Soybean aphid, Aphis glycines Matsumura, has drastically changed soybean pest management in the North Central region. To date, SBA can be successfully managed by timely scouting and foliar insecticides. Host plant resistance is the newest soybean aphid management tool and is complementary to existing chemical control. Disciplines Agriculture | Agronomy and Crop Sciences | Entomology Comments This article is published as Hodgson, E. W., and G VanNostrand. Soybean Aphid Efficacy Screening Program, 2016. Arthropod Management Tests 42 (2017): tsx045. doi: 10.1093/amt/tsx045. Creative Commons License This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License This article is available at Iowa State University Digital Repository: https://lib.dr.iastate.edu/ent_pubs/505 SOYBEAN: Glycine max L., ‘NK S24-K2’ Soybean Aphid Efficacy Screening Program, 2016* Erin W. Hodgson and Greg VanNostrand Department of Entomology, Iowa State University, 103 Insectary Bldg., Ames, IA 50011-3140, Phone: (515) 294-2847, Fax: (515) 294-7406 (ewh@iastate.edu), Corresponding author, e-mail: ewh@iastate.edu, and Department of Entomology, Iowa State University, 021 Insectary Bldg., Ames, IA 50011-3140, Phone: (515) 294-6124, Fax: (515) 294-7406 (gregvn@iastate.edu) Subject Editor: Clyde Sorenson Soybean j Glycine max Soybean aphid j Aphis glycines Soybean aphid, Aphis glycines Matsumura, has drastically changed soybean pest management in the North Central region. To date, SBA can be successfully managed by timely scouting and foliar insecticides. Host plant resistance is the newest soybean aphid management tool and is complementary to existing chemical control. In 2016, we established plots at two Iowa State University Research Farms (Northeast and Northwest) on 27 May and 27 May respectively. NK S24-K2 soybean variety was used for all treatments. Plots were arranged in a RCB design with four replications. Each plot was six rows in width and 50 ft in length at the Northeast location and six rows in width by 44 ft in length at the Northwest location. Treatments containing a seed treatment were applied by Syngenta. For Northeast location, foliar treatments were applied using a backpack sprayer and TeeJet (Springfield, IL) twinjet nozzles (TJ 11002) with 20 gpa at 40 lb psi. For Northwest location, foliar treatments were applied using a custom sprayer and TeeJet (Springfield, IL) flatfan nozzles (TJ 8002) with 14 gpa at 40 lb psi. Soybean aphids were counted on randomly selected whole plants within each plot. To estimate the total exposure of soybean plants to soybean aphid, we calculated cumulative aphid days (CAD) based on the number of aphids per plant counted on each sampling date. Yields (bushels/acre) were determined by weighing grain with a hopper and corrected to 13% moisture. One-way ANOVA was used to determine treatment effects within each experiment. Means separation for all studies was achieved using a least significant difference test (a1⁄40.10). All statistical analyses were performed using SAS software. The plots at each farm were uniformly colonized in late July and there was light soybean aphid pressure at both locations until after full bloom, or early August. At the Northeast location, foliar applications were made on 18 Aug when plants were in the R5 growth stage. Soybean aphids in the untreated check plots averaged 15 per plant days days prior to the 18 Aug application and peaked on 25 Aug at 115 aphids per plant. The untreated check had 1,543 CAD and was significantly higher than many foliar insecticides. There were significant reductions in aphids with many of the foliar insecticides versus the untreated check (Table 1). There was some variability in yield between treatments, but most products labeled for soybean aphid were not statistically different. At the Northwest farm, foliar applications were made 9 Aug when plants were in the R5 growth stage. Soybean aphid populations in the untreated check plots averaged 282 per plant one day prior to the 24 Aug application and peaked on 30 Aug at 705 aphids per plant. The untreated check had the significantly higher CAD compared to treatments with foliar insecticides. There were reductions in aphids with all foliar insecticides versus the untreated check (Table 2). Yield between treatments varied from 70-92 bushels per acres, and we believe the differences were due to soybean aphid seasonal exposure. * This research was supported by industry gifts of seed, product and research funding. VC The Author 2017. Published by Oxford University Press on behalf of the Entomological Society of America. 1 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com Arthropod Management Tests, 2017, 1–2 doi: 10.1093/amt/tsx045 Section F: Field & Cereal Crops D ow naded rom http/academ ic.p.com am t/article-abs2/1/tsx045/3775683 by 0460000 user on 15 April 2019