Halosulfuron reduces purple nutsedge (Cyperus rotundus) tuber production and viability

Authors: Webster, Theodore; GREY, TIMOTHY - University Of Georgia

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2013
Publication Date: 6/1/2013
Citation: Webster, T.M., Grey, T.L. 2013. Halosulfuron reduces purple nutsedge (Cyperus rotundus) tuber production and viability. Weed Science Society of America Meeting Abstracts. #44.

Interpretive Summary:

Technical Abstract: Purple nutsedge is one of the most troublesome weeds of fresh-market vegetable crops in the Southern U.S. A perennial weed, purple nutsedge reproduces vegetatively by producing chains of tubers. Halosulfuron is an effective means of controlling purple nutsedge foliage and is registered for use in several vegetable crops. However, the effect of halosulfuron on purple nutsedge tuber production and tuber viability has not been evaluated. A single pre-sprouted purple nutsedge tuber was transplanted into outdoor microplots in middle April in 2011 and 2012. After six weeks of growth, six rates of halosulfuron (7 to 208 g ai ha-1) were applied POST. A nontreated control (NTC) was also included. Treatments were arranged as a randomized complete block design, blocked by emerged shoot numbers at application, and had five replications. All shoots emerged at the time of application were marked with plastic rings; this allowed for classification of tubers at exhumation of 1) tubers attached to shoots that were emerged at time of application, 2) tubers attached to shoots that emerged after application, and 3) tubers without an aerial shoot during the study. Seven weeks after application, the tubers in the microplots were exhumed, tubers classified, quantified, and viability evaluated. In the NTC, there were 530 total tubers, with a hyperbolic decay regression describing the tuber population with increasing halosulfuron dose. At 52 g ha-1 (common 1X dose in vegetables) there was a 79% reduction in total tuber population. There were no differences among treatments in number of tubers attached to emerged aerial shoots (31 to 43) at the time of application. However, the viability of these tubers was reduced to 16% at the 1X rate. In the NTC, there were 200 tubers that were attached to shots that emerged following halosulfuron application, while the 1X dose reduced tuber numbers 75%. However, this new shoot emergence may give the initial impression to the grower that the treatment was ineffective. Viability of these tubers was 28% at the 1X rate of halosulfuron, suggesting the action of the herbicide may have rendered the tuber nonviable after new shoots were produced. The final classification of tubers is the tubers that did not have an aerial shoot during the study. These are tubers in which apical dominance suppressed shoot development or were the most recent tubers to develop. Of the three classes, these were the most numerous in the NTC, with 294 tubers. At the 1X rate of halosulfuron, tuber production was reduced 93%, with only 14% viability of the tubers that were produced. Halosulfuron is an effective herbicide that control purple nutsedge foliage, but also reduces the number of new tubers produced and overall tuber viability. This could be an important component used to reduce the long-term population density of this weed.