Efficacy and Economics of Weed Management in Glyphosate-Resistant Corn (Zea mays)¹

Abstract

Field experiments were conducted in 1997 and 1998 near Columbia and Novelty, MO, and Urbana, IL, to evaluate crop injury, weed control, corn yield, and net economic returns provided by weed control programs in glyphosate-resistant corn. The herbicide programs evaluated included acetochlor preemergence (PRE) followed by (fb) glyphosate with or without atrazine postemergence (POST) and total POST programs consisting of single and sequential applications of glyphosate alone and tank-mixed with actochlor, atrazine, or both. Metolachlor PRE fb dicamba plus atrazine POST and metolachlor plus atrazine PRE were included for comparison. In the total POST treatments, mid-post (MPOST) applications provided better control than early-post (EPOST) applications on weeds that germinated throughout the growing season such as shattercane and common cocklebur, but also resulted in yield reductions of up to 23% caused by early-season weed competition. The addition of atrazine to glyphosate POST generally increased control of common cocklebur, morningglory species, and common waterhemp. EPOST or PRE fb EPOST applications generally provided higher yields than MPOST treatments, although MPOST treatments often provided equal or greater weed control at midseason. Treatments including two herbicide applications tended to provide greater weed control, yield, and profit than those with a single application. Input costs for glyphosate-resistant corn are slightly higher than nontransgenic hybrids. However, net economic returns are similar and the use of glyphosate POST allows greater flexibility in POST weed management decisions.

The Biology of Invasive Alien Plants in Canada. 3. Amaranthus tuberculatus (Moq.) Sauer var. rudis (Sauer) Costea & Tardif

“…rudis in corn in Missouri required two applications of glyphosate or glufosinate in combination with residual herbicides (Hellwig et al 2003). Single applications were much less effective, unless combined with a residual herbicide, such as atrazine in corn, or sulfentrazone in soybeans Dirks et al 2000a;Johnson et al 2000;Beyers et al 2002;Nolte and Young 2002a, b). Control with single glyphosate applications in soybeans increased as row spacing decreased from 76 to 19 cm .…”

Weed management options in transgenic stacked and non transgenic maize (Zea mays) hybrids-A review

“…Twomlow et al (1997) reported that in maize the driest soil profiles and lowest yields were observed under the unweeded control. Johnson et al (2000) described that increasing corn population to the recommended level would be the first approach to increase corns competitive ability against weeds using narrow rows which appears to have less potential for improving weed control. Sinha et al (2000) reported that nutrient depletion by weeds was minimum under hand weeding while it was maximum 23.18 kg N, 4.92 kg P and 27.83 kg Kha -1 under weedy check in maize in calcareous soils of North Bihar.…”

“…Glyphosate-resistant maize is advantageous compared to conventional hybrids. According to Johnson et al (2000), two post emergence glyphosate applications on corn can provide better weed control than a single glyphosate application, especially if interfering weeds are controlled at heights less than 15 cm. Application of glyphosate at 0.84 kg ha -1 followed by 0.63 kg ha -1 as early post emergence provided effective control of shattercane (100 per cent) and giant foxtail (99 per cent) while single application of glyphosate provided only 58 per cent and 69 per cent of shattercane and giant foxtail, respectively at Columbia (Hans and Johnson, 2002).…”

“…Ravisankar et al (2011) reported that application of glyphosate at 1800 g a.e/ha in transgenic maize hybrid gave maximum net return and benefit: cost ratio as compared to conventional maize hybrids. Johnson et al (2000) reported that net income was positively correlated with transgenic maize yield. All glyphosate based treatments produced higher net income while least profit was recorded with without glyphosate and unweeded control.…”

Using Herbicide Programs to Control Weeds in Corn (Zea mays L.) and Cotton (Gossypium hirsutum L.)

“…The development of herbicide-resistant crops allows weed control by nonselective postemergence (POST) herbicides, such as glyphosate and glufosinate, widening the array of weed management programs available to producers [5][6][7]. Both glyphosate and glufosinate control a wide range of weeds in herbicide-resistant crops [7] with little, if any, crop injury [8,9].…”