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Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/14/2014 Publication Date: 12/20/2014 Citation: Nandula, V.K. 2014. Italian ryegrass (Lolium multiflorum) and corn (Zea mays)competition. American Journal of Plant Sciences. 5(21):3914-3924. Interpretive Summary: Italian ryegrass is an annual/biennial grass that is typically used as a pasture crop or a cover crop along roadsides, rights-of-way, and industrial areas. Glyphosate-resistant (GR) Italian ryegrass populations have been documented around the world, mostly in orchard and vineyard situations. The first evidence of evolved GR Italian ryegrass in row/agronomic crops was reported from Washington County, Mississippi in 2005. GR Italian ryegrass populations can jeopardize preplant burndown options in reduced-tillage crop production systems, thereby, delaying planting operations. Scientist from the Crop Production Systems Research Unit (USDA-ARS) conducted field studies to understand the effects of competition of GR and glyphosate-susceptible (GS) Italian ryegrass on corn growth and yield in 2012 and 2013. Corn height was greater in 2012 than 2013 at comparable stages of the growing season, due to a cooler and wetter early season in 2013 than 2012. Averaged across weed densities, corn density (both early and late season) and yield were higher in the GS than the GR population, but Italian ryegrass biomass was similar for both populations. Averaged across Italian ryegrass populations, corn density (both early and late season), and yield were inversely proportional to Italian ryegrass density. In summary, GR Italian ryegrass significantly reduced corn density and yield more than the GS population. Technical Abstract: Italian ryegrass is an annual/biennial grass that is typically used as a pasture crop or a cover crop along roadsides, rights-of-way, and industrial areas. Glyphosate-resistant (GR) Italian ryegrass populations have been documented around the world, mostly in orchard and vineyard situations. The first evidence of evolved GR Italian ryegrass in row/agronomic crops was reported from Washington County, Mississippi in 2005. GR Italian ryegrass populations can jeopardize preplant burndown options in reduced-tillage crop production systems, thereby, delaying planting operations. The effects of competition of Italian ryegrass on crop growth and yield are poorly understood. A field study was conducted in the 2012 growing season and repeated in the 2013 growing season. GR and susceptible (GS) Italian ryegrass populations were established in the greenhouse and transplanted in prepared corn row beds in the fall of 2011 and 2012 at 0, 1, 2, 3, and 4 plants meter-1 of crop row. Italian ryegrass plants overwintered and developed over the following spring-summer. Glyphosate was applied at 1.26 kg ae/ha (1.5 X of labeled rate) in the spring to burndown the Italian ryegrass plants and corn was planted into the ryegrass residue 2-3 wk later. Current corn production practices were followed. Corn density (early and late season), height (early season), and yield and Italian ryegrass biomass (early-mid season) measurements were recorded during both years. Corn height was greater in 2012 than 2013 at comparable stages of the growing season, due to a cooler and wetter early season in 2013 than 2012. Averaged across weed densities, corn density (both early and late season) and yield were higher in the GS than the GR population, but Italian ryegrass biomass was similar for both populations. Averaged across Italian ryegrass populations, corn density (both early and late season), and yield were inversely proportional to Italian ryegrass density. In summary, Italian ryegrass significantly reduced corn density up to 60% and yield up to 51% and reduction was greater with increasing weed density, more with GR than GS. Studies are underway to study inter population competition in Italian ryegrass and investigate allelopathic effects of Italian rygrass on selected crops. |
