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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #315740
Title: Evaluation of control of napiergrass (Pennisetum purpureum) with tillage and herbicides

Author
item LI, XIAO - Auburn University
item GREY, T - University Of Georgia
item Webster, Theodore
item Anderson, William - Bill
item CUTT III, G - Monsanto Corporation

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2015
Publication Date: 10/1/2015
Citation: Li, X., Grey, T.L., Webster, T.M., Anderson, W.F., Cutt III, G.S. 2015. Evaluation of control of napiergrass (Pennisetum purpureum) with tillage and herbicides. Invasive Plant Science and Management. 8(4):393-400.

Interpretive Summary: With increasing demands for renewable energy for transportation and power sectors, the need for alternate fuel sources began to rise during the early part of the 21st century. Cellulosic biofuel production was targeted as potentially providing practical alternatives to crude oil-based liquid fuels. Napiergrass has high biomass yields and garnered interest as a possible feedstock for cellulosic biofuel production. Also known as elephantgrass, napiergrass is a tetraploid, C4 perennial grass as a native tropical species but adapted to subtropical areas throughout the world. With biomass yields in excess of 45 Mg ha-1 in a full season’s growth, napiergrass has been widely renowned to have the highest biomass productivity among herbaceous plants. While considered as a potential biofuel crop, napiergrass is also a Category I Invasive Exotic species as listed by the 2013 Florida Exotic Pest Plant Council in all regions of the state; Category I Invasive Exotic species are listed as those altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives. An important aspect of a biofuel species will be how to manage populations when growers want to transition into the next crop in a field. Imazapyr plus glyphosate consistently controlled of napiergrass as compared to diclosulam plus glyphosate, sulfentrazone plus glyphosate or tillage. One application of imazapyr plus glyphosate controlled napiergass 74 to 94% and reduced napiergrass stem height 94 and 85% as compared to the nontreated control. When diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage was used alone with no sequential herbicides, napiergrass control ranged from 12 to 33%. When diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage treatments were followed by two sequential applications of either sethoxydim or glyphosate, napiergrass control varied from 45 to 99%. Napiergrass yield in dry biomass production was reduced 86% by imazapyr plus glyphosate. Diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage alone was not effective in reducing napiergrass dry biomass yields (<47% control). When imazapyr plus glyphosate had sequential applications of sethoxydim or glyphosate, napiergrass biomass was reduced >88%. A multiple season approach will likely be needed, as no single tillage or herbicide(s) application will eradicate napiergrass.

Technical Abstract: Napiergrass has potential as a cellulosic biofuel crop because of its rapid growth habit in the southern US. But it is also considered as a potential invasive species as listed by the Florida Exotic Pest Plant Council. In order for field renovation, information about napiergrass control in response to tillage and herbicides is required. Field studies were initiated to evaluate control of napiergrass established in fields for over 3 years at Plains and Tifton, GA. For tillage and POST herbicides, imazapyr plus glyphosate provided consistent control of napiergrass as compared to diclosulam plus glyphosate, sulfentrazone plus glyphosate or tillage, in terms of visual injury, stem height and dry biomass reduction. One application of imazapyr plus glyphosate provided 74 and 94% control, and reduced napiergrass stem height 94 and 85% as compared to the nontreated control (NTC at 0%) in Plains and Tifton, respectively. When diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage was used alone with no sequential herbicides, napiergrass control ranged from 12 to 33%. When diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage treatments were followed by two sequential applications of either sethoxydim or glyphosate, napiergrass control varied from 45 to 99%. Reductions in stem heights were reflective of injury 47 days after final herbicide applications (May-June). Napiergrass yield in dry biomass production was reduced by imazapyr plus glyphosate to 13 and 14% as compared to the NTC 100%, at Plains and Tifton, respectively. Diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage alone was not effective in reducing napiergrass dry biomass yields ranging from 53 to 99% of the NTC 100%. When imazapyr plus glyphosate had sequential applications of sethoxydim or glyphosate, napiergrass biomass was 1 to 12% of the NTC 100%. In contrast, diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage followed by sequential applications of sethoxydim or glyphosate, napiergrass dry biomass was reduced to 9 to 54% of the NTC 100%. Tillage plus two applications of sethoxydim or glyphosate exhibited control potential since they provided similar level of napiergrass control similar to imazapyr based treatments. Tillage plus multiple applications of sethoxydim or glyphosate offers flexibility to crop rotations, as compared to the residual herbicide imazapyr which has many crop rotation restrictions due to carryover concerns.