title: Impact of Lepidoptera (Crambidae, Noctuidae, and Pyralidae) Pests on Corn Containing Pyramided Bt Traits and a Blended Refuge in the Southern United States.
abstract: Blended refuge for transgenic plants expressing Bacillus thuringiensis (Bt) toxins has been approved in the northern United States as a resistance management strategy alternative to a structured refuge. A three-year study (2012-2014) was conducted with 54 trials across nine states in the southern United States to evaluate plant injury from lepidopteran pests of corn and yield in a corn hybrid expressing Cry1F × Cry1Ab × Vip3Aa20 (Pioneer Brand Optimum Leptra) planted as a pure stand and in refuge blends of 5, 10, and 20% in both early and late plantings. Injury by corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), and fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), was generally proportional to the percentage of non-Bt corn within each refuge blend. Across locations, ear injury in plots with 100% Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra) corn ranged from no injury to a maximum of 0.42 cm(2) per ear in Mississippi in 2013. Leaf injury ratings in 100% non-Bt plots in early and late planted trials in 2014 were 86- and 70-fold greater than in 100% Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra) plots. Plants in plots with blended refuges had significantly greater leaf injury in 2012 (5, 10, and 20% refuge blends), in the early-planted corn in 2013 (10 and 20% only), and in both early- and late-planted corn in 2014 (20% only) as compared with leaf injury in a pure stand of Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra) seen during these years. Corn ears in plots with blended refuges also had significantly greater area of kernels injured in 2012 (5, 10, and 20%), in early- and late-planted corn in 2013 (5, 10, and 20%), and in early (10 and 20% only)- and late-planted corn (5, 10, and 20%) in 2014 as compared with ear injury in a pure stand of Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra) seen during these years. Infestations of southwestern corn borer, Diatraea grandiosella Dyar (Lepidoptera: Crambidae), were also significantly reduced by Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra). Despite these differences in injury, yield averaged across locations varied among refuge blends only in the late-planted trials in 2013, with greater yields in the 0% refuge blend than in the 20% blend; however, when examining yield separately by location, only two of nine locations had higher yields in the 100% Bt plots than in any of the blended refuge plots. As a complement to studying the contribution of blended refuge to delaying resistance, quantifying injury and yield in a range of refuge blends is a necessary step to provide management information on the range of lepidopteran pests that occur in the southern United States.
authors.affiliation: Department of Agricultural and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, 2200 Pocket Rd., Florence, SC 29506-9727 (freayjo@clemson.edu).
authors.forename: F P F
authors.initials: FP
authors.lastname: Reay-Jones
authors.affiliation: Department of Entomology, University of Kentucky, S-225 Ag North, Lexington, KY 40546 (rbessin@uky.edu).
authors.forename: R T
authors.initials: RT
authors.lastname: Bessin
authors.affiliation: Texas A&M AgriLife Research & Extension Center, 10345 State Hwy 44, Corpus Christi, TX 78406 (mjbrewer@ag.TAMU.edu).
authors.forename: M J
authors.initials: MJ
authors.lastname: Brewer
authors.affiliation: Department of Entomology, UGA-Griffin Campus, 1109 Experiment Street, Griffin, GA 30223 (gbuntin@uga.edu).
authors.forename: D G
authors.initials: DG
authors.lastname: Buntin
authors.affiliation: Department of Entomology & Plant Pathology, Mississippi State University, Mississippi State, MS 39762 (acatchot@entomology.msstate.edu).
authors.forename: A L
authors.initials: AL
authors.lastname: Catchot
authors.affiliation: Delta Research & Extension Center, Mississippi State University, P.O. Box 197, Stoneville, MS 38776 (dcook@drec.msstate.edu).
authors.forename: D R
authors.initials: DR
authors.lastname: Cook
authors.affiliation: 201 Extension Hall, Auburn University, AL 36849 (flandkl@auburn.edu).
authors.forename: K L
authors.initials: KL
authors.lastname: Flanders
authors.affiliation: LSU AgCenter, Macon Ridge Station, 212A Macon Ridge Rd., Winnsboro, LA 71295 (dkerns@agcenter.lsu.edu).
authors.forename: D L
authors.initials: DL
authors.lastname: Kerns
authors.affiliation: Texas AgriLife Research & Extension Center, Lubbock, TX 79403 (pporter@ag.tamu.edu).
authors.forename: R P
authors.initials: RP
authors.lastname: Porter
authors.affiliation: Department of Entomology, North Carolina State University, Vernon G. James Research and Extension Center, Plymouth, NC 27962 (ddreisig@ncsu.edu).
authors.forename: D D
authors.initials: DD
authors.lastname: Reisig
authors.affiliation: West Tennessee Research and Education Center, 605 Airways Blvd., Jackson, TN 38301 (sdstewart@utk.edu).
authors.forename: S D
authors.initials: SD
authors.lastname: Stewart
authors.affiliation: DuPont Pioneer, P. O. Box 1150, Johnston, IA 50131 (marlinrice@gmail.com), and marlinrice@gmail.com.
authors.forename: M E
authors.initials: ME
authors.lastname: Rice
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry* / Q000235:genetics; D001426:Bacterial Proteins / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000494:pharmacology*; D007305:Insecticide Resistance; D009036:Moths / Q000502:physiology*; D010572:Pest Control, Biological; D014481:United States; D003313:Zea mays / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C406926:CRY1BD protein, Bacillus thuringiensis
keywords: Bacillus thuringiensis; Helicoverpa zea; Optimum Leptra; Spodoptera frugiperda; maize