Four glyphosate resistant corn (Zea mays L.) hybrids, a glufosinate-ammonium resistant hybrid, and a conventional atrazine resistant hybrid gown at Stoneville, MS in 2005, 2006, and 2007 with furrow irrigation were treated with their respective herbicides and their growth, yield, and mycotoxin incidence were compared with untreated cultivated plots. Leaf area index (LAI) and dry matter accumulation (DMA) were collected on a weekly basis beginning at growth stage V3 and terminating at anthesis. Crop growth rates (CRGs) and relative growth rates (RGRs) were calculated. Plots were later harvested, yield and yield component data collected, and kernel samples analyzed for aflatoxin and fumonisin. Leaf area index, DMA, CRG, and RGR were not different among the herbicide treated plots and from those that were cultivated. Curves for LAI and DMA were similar to those previously reported. Aflatoxin and fumonisin were relatively low in all plots. Herbicide application or the lack thereof had no negative impact on the incidence of kernel contamination by these two mycotoxins. Herbicides, especially glyphosate on resistant hybrids, have no negative effects on corn yields or kernel quality in corn produced in a humid subtropical environment. 1. Introduction Herbicides have been a standard method of weed control in corn for over five decades, especially with the introduction of relatively low-cost and effective soil-applied pre-emergence compounds [1]. Atrazine, [2-Chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine] allowed producers to increase their profits by chemically controlling a large number of weed species that robbed corn of needed water, light, and nutrients. The advent of corn hybrids resistant to the herbicide glyphosate [N-(phosphonomethyl)glycine] has expanded the number of weed species that can be chemically controlled, including several noxious pests not controlled by other corn herbicides. Corn hybrids are also available that are resistant to the herbicide glufosinate-ammonium [2-amino-4-(hydroxymethylphosphinyl) butanoic acid] which has nearly as broad of a range of weed species controlled as glyphosate. Virtually all major seed corn companies now offer hybrids in all maturity ranges resistant to one or the other of these two latter herbicides. As of 2005, glyphosate-resistant hybrids were grown on nearly 40% of the total U.S. corn hectarage while glufosinate-ammonium-resistant hybrids were produced on about 7% of the total corn hectarage [2]. Atrazine was applied to about 66% of the total U.S. corn hectarage. Glyphosate’s mode of action involves
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