Crop Protection 21 (2002) 375–381 Insect management and herbicide tolerance in near-isogenic sister lines of transgenic and non-transgenic sweet corn Douglas J. Doohan a, *, Joel Felix a , Jim Jasinski b , Celeste Welty c , Matthew D. Kleinhenz a a DepartmentofHorticultureandCropScience,TheOhioStateUniversity,OARDC,1680MadisonAve.,Wooster,OH44691,USA b OhioStateUniversityExtension,303CorporateCenterDr.,Vandalia,OH45377-1171,USA c DepartmentofEntomology,TheOhioStateUniversity,1991KennyRd.#111,Columbus,OH43120,USA Received 9 July 2001; received in revised form 6 August 2001; accepted 31 August 2001 Abstract Pest management systems were evaluated in three near-isogenic lines of transgenic and non-transgenic sweet corn. The genetic transformation was reputed to confer resistance to corn earworm (Helicoverpazea) and European corn borer (Ostrinianubilalis), and increase tolerance to the herbicide glufosinate. Plots were planted with either a transgenic line or a non-transgenic sister line. Transgenic and non-transgenic varieties were treated with a herbicide; either glufosinate or bentazon, respectively, applied post- emergence.Earsofthenon-transgenicvarietieswereprotectedbysprayinginsecticidesevery3–4days.Transgenicvarietieswerenot sprayed. Glufosinate caused temporary chlorosis (5% or less) and stunting (6% or less) of transgenic sweet corn in one experiment. Bentazon did not injure non-transgenic varieties. Corn earworm and European corn borer control in transgenic sweet corn was superiortothatachievedinnon-transgenicvarietiessprayedwithinsecticides.Damagedearsoftransgenicvarietiesrangedfrom0% to6%andmostdamagewasrestrictedtothetipofthesilkend.Afewsmall,moribundlarvaewererecovered.Incontrast,40%of non-transgenic varieties, on average, had damaged ears, despite regular spraying of insecticides. Ears of non-transgenic varieties were damaged more severely and many late-instar larvae were recovered. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Insect feeding resistance; Crop injury; Glufosinate; Bentazon 1. Introduction Sweet corn (Zea mays L.) is an important vegetable crop in Ohio and is grown on about 7000ha annually (USDA, 2001). Production within the state is sold entirelyasfreshearsofcorn.Consumersdemandahigh qualityproductandthereisessentiallyzerotolerancefor insect infested or damaged ears. An array of carbamate, organophosphate and synthetic pyrethroid insecticides are recommended for control of corn earworm (Heli- coverpazea Boddie), and European corn borer (Ostrinia nubilalis Hubner), the most important insect pests that directly damage the ear. During silking, insecticides must be applied to prevent damage by larvae as soon as adults of corn earworm or European corn borer are detected by traps (Adams and Clark, 1995; Flood et al., 1995). Insecticides must be reapplied every 3–5 days for corn earworm and every 5–7 days for European corn borer. During periods of high temperature or heavy flights of adult moths, short reapplication intervals are recommended. Although the average sweet corn acre is treated with insecticide 2.75 times per year in Ohio (Huelsman, 2001; Waldron et al., 1992), plantings maturing in late summer are usually treated 4–7 times due to high pest pressure. Optionsforweedcontrolinsweetcornarelimiteddue to few registered herbicides. Herbicides, or herbicides plus cultivation are the preferred methods of weed control used by the majority of growers in Ohio. In a recent survey conducted by Doohan (unpublished data) approximately 50% of respondents indicated that cultivation is required to augment control obtained with herbicides. Triazine herbicide-resistant broadleaf weeds and late emerging annual grasses are poorly controlled by the standard treatments of atrazine tank-mixed with either s-metolachlor, alachlor, or s-dimethenamid. Pen- dimethalinmaybeappliedaftersweetcornemergenceto control triazine-resistant lamb’s quarters (Chenopodium *Corresponding author. Tel.: +1-330-202-3593; fax: +1-330-263- 3887. E-mailaddress: doohan.1@osu.edu (D.J. Doohan). 0261-2194/02/$-see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S0261-2194(01)00106-5