Science of the Total Environment 497–498 (2014) 534–542 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv A multi-year field study to evaluate the environmental fate and agronomic effects of insecticide mixtures Sara A. Whiting a,1, Katherine E. Strain a, Laura A. Campbell b,2,BryanG.Youngb,3,MichaelJ.Lydya,⁎ a Center for Fisheries, Aquaculture, and Aquatic Sciences and Department of Zoology, 1125 Lincoln Dr., Southern Illinois University, Carbondale, IL 62901, USA b Plant, Soil, and Agricultural Systems Department, 1205 Lincoln Dr., Southern Illinois University, Carbondale, IL 62901, USA HIGHLIGHTS GRAPHICAL ABSTRACT • Cry1Ab proteins were found in soil and runoff water, but dissipated quickly. • Clothianidin was found in all environ- mental matrices. • Tefluthrin was measured at high levels in soil, runoff water, and runoff sedi- ment. • The addition of tefluthrin to Bt corn had no impact on grain yield or pest dam- age. article info abstract Article history: A mixture of insecticides used in corn production was monitored over a three-year period in a field study to de- Received 19 May 2014 termine how long each persists in the environment, where each insecticide travels within the corn field, and the Received in revised form 29 July 2014 efficacy of using soil-applied insecticides with genetically modified corn. The genetically modified corn contained Accepted 29 July 2014 the insecticidal Cry1Ab and Cry3Bb1 proteins (Bt corn) and the Cry1Ab protein was found to persist only during Available online 23 August 2014 the corn growing season in soil, runoff water, and runoff sediment with highest concentrations measured during fi Editor: Adrian Covaci pollination. Very low concentrations of Cry1Ab proteins were measured in soil collected in the non-Bt corn eld, and no Cry1Ab proteins were detected in shallow groundwater or soil pore water. Clothianidin, a neonicotinoid Keywords: insecticide used as a seed coating, was detected in all matrices and remained persistent throughout the year in Insecticide soil pore water. Tefluthrin, a pyrethroid insecticide applied at planting to control corn rootworm larvae Genetically modified corn (Diabrotica spp., Coleoptera: Chrysomelidae) populations, was consistently detected in soil, runoff water, and Tefluthrin runoff sediment during the corn growing season, but was not detected in groundwater or soil pore water. Clothianidin Tefluthrin did not have an effect on root damage from corn rootworm larvae feeding to Bt corn, but did prevent Cry1Ab damage to non-Bt corn. A slight reduction in grain yield was observed in the non-Bt, no tefluthrin treatment when compared to all other treatments, but no significant difference in grain yield was observed among Bt ⁎ Corresponding author. Tel.: +1 618 453 4091. E-mail addresses: [email protected] (S.A. Whiting), [email protected] (K.E. Strain), [email protected] (L.A. Campbell), [email protected] (B.G. Young), [email protected] (M.J. Lydy). 1 Present address: ABC Laboratories, 7200 E ABC Lane, Columbia, MO 65202, USA. 2 Present address: Dow AgroSciences, 9330 Zionsville Rd., Indianapolis, IN 46268, USA. 3 Present address: Department of Botany and Plant Pathology, Purdue University, 915 West State St., W. Lafayette, IN 47907, USA. http://dx.doi.org/10.1016/j.scitotenv.2014.07.115 0048-9697/© 2014 Elsevier B.V. All rights reserved. S.A. Whiting et al. / Science of the Total Environment 497–498 (2014) 534–542 535 corn treatments regardless of soil insecticide application. In the current study, the use of tefluthrin on Bt corn did not significantly affect crop damage or yield, and tefluthrin may travel off-site in runoff water and sediment. © 2014 Elsevier B.V. All rights reserved. 1. Introduction (DCM), Optima grade acetonitrile (ACN), and HPLC grade submicron fil- tered water. Trifluoroacetic acid (≥98%) was purchased from Sigma- The corn rootworm complex, Diabrotica spp. (Coleoptera: Aldrich. The solid phase extraction (SPE) cartridges used to clean sam- Chrysomelidae), has been a major pest of field corn (Zea mays) in the ple extracts were 6 mL dual layer Supelclean™ ENVI™-Carb II/primary United States for decades causing substantial crop damage and; the- secondary amine (PSA) 300/600 mg (Supelco Analytical). refore, reductions in corn grain yield (Dun et al., 2010). Transgenic or genetically modified (GM) corn was introduced in the United States in 2.2. Field site 1996 as a new method to control corn pests with a specificmodeofac- tion so that non-target and beneficial insects were not directly affected Research was conducted on a 36 ha farm in Christian County, Illinois, by its use (Roush, 1998). Currently registered insect-protected GM corn USA. Three replicates of six different treatments were planted in 2011, contains genetic code from the bacterium Bacillus thuringiensis Berliner 2012, and 2013, with the treatments planted in the same locations in (Bt) and the corn produces insecticidal crystal protein endotoxins the field in each of the three years. The treatments included: (1) Bt corn (Cry proteins) that are lethal to target pest species when ingested MON88017 × MON810 with the insertion of Cry3Bb1 and Cry1Ab (Roush, 1998). genes, respectively, with no tefluthrin; (2) Bt corn MON88017 × Since the first Bt crop was released in 1996 and the first trait for MON810 with half the normal rate of tefluthrin applied which was rootworm control was released in 2003, adoption of this technology − 0.06 kg ha 1; (3) Bt corn MON88017 × MON810 with the full rate of has increased exponentially in the United States from 8% of total − tefluthrin 0.11 kg ha 1; (4) a near isoline of non-Bt corn with no corn acreage grown in the United States in 1997 to 90% in 2013, tefluthrin applied; (5) non-Bt corn with half the normal rate of tefluthrin while some conventional insecticide use has decreased (USDA, 2013). applied; and (6) non-Bt cornwiththefullrateoftefluthrin applied. Only However, recent studies found that some rootworm populations have the Cry1Ab protein (which targets Lepidopteran pests) was quantified in developed evolutionary resistance to the GM corn trait Bt-Cry3Bb1 environmental matrices due to lack of commercial availability of stan- (Gassmann et al., 2011, 2012). A recent pest management strategy has dards of the Cry3Bb1 protein. There are differences in protein expression been the addition of seed coatings with neonicotinoid insecticides within the plant (e.g. Cry3Bb1 found at high levels in roots, and Cry1Ab (example: clothianidin). Neonicotinoid insecticides, like clothianidin, found at high levels in ear tissue — see Table 5 in USEPA, 2010), but are the most widely used insecticides in the world (Goulson, 2013), based on a literature review and the capabilities in our laboratory, it and almost all seed corn purchased in the United States is coated with was determined that Cry1Ab could be examined in the environment a neonicotinoid insecticide (Mullin et al., 2005). Conventional soil insec- and compared to other Bt Cry proteins. Corn seed from all treatments ticide application of the pyrethroid, tefluthrin, at planting is another was uniformly coated with 0.25 mg of the active ingredient clothianidin strategy to control rootworm genetic resistance to Bt crops, although per seed. In order to replicate typical field conditions of an average the benefits of this method have not been researched in depth grower's practice in Central Illinois, all seed was treated with a seed treat- (Petzold-Maxwell et al., 2013). ment, therefore, there was no field control for clothianidin. There were no The current study fills important gaps in knowledge about the envi- foliar applications of fungicides to any treatment, however some fungi- ronmental fate and agronomic efficacy of the combination of conven- cides were used as a component of the seed coating. Fungicides in the tional insecticides with Bt corn production. Concentrations of each seed treatment varied between years, but were always uniformly applied. insecticide were measured in runoff water and sediment, groundwater, Seed was planted at a rate of 86,488 seeds per ha in 2011 and 2012 and at soil pore water, and soil before, during, and after the corn growing sea- a rate of 84,017 seeds per ha in 2013. Supplemental fertilizer including ni- son throughout three years at a research site in central Illinois using a trogen, phosphorus, and potassium were applied to each treatment every continuous corn, no-till agricultural system. Corn grain yields and root year as per standard local corn production practices. All treatments had damage from pests were also measured in order to determine agronom- the same rate of herbicides isoxaflutole, thiencarbazone-methyl, and ic efficiency of using this corn production system. The goal of the study glyphosate applied within a week after planting each year to provide es- was to determine how long these insecticides persist in the environ- sentially a weed-free experiment. ment, where the insecticides are found in the environment after appli- cation, and if the combination of insecticides affects grain yields and pest damage. 2.3. Field sample collection Groundwater was collected from seven - 5.08 mm diameter, 4 m 2. Methods deep polyvinylchloride (PVC) wells spaced so that each treatment was represented at least once. Wells were purged prior to sample collection 2.1. Solvents and chemicals with a submersible pump (Water Spout II Super Purge Pump, Forestry Suppliers, Inc., Jackson, MS, USA) (USEPA, 2004). Soil pore water was Purified Cry1Ab protein was purchased from Abraxis, LLC collected from lysimeters buried 1 m in the ground (Large volume (Warminster, PA, USA). Neonicotinoids including clothianidin and “Ultra” sampler, Soilmoisture Equipment Corp., Santa Barbara, CA, acetamiprid were 99.9% pure (Sigma-Aldrich, St. Louis, MO, USA) and USA). Based on Farm Service Agency aerial images, slopes on the re- imidacloprid (ChemService, West Chester, PA, USA) was 99.5% pure.