Published online by Cambridge University Press: 20 January 2017
Weeds persist and cause economic losses in agricultural systems because theyexploit underused portions of that system. Reducing the effect of weeds onagroecosystems begins with minimizing the number of propagules (e.g., seedsand tubers) that are produced and returned to the soil. Purple nutsedge is aproblematic weed around the globe, persisting between growing seasons astubers in the soil. Halosulfuron is an effective herbicide for controllingpurple nutsedge foliage and is used in corn and several vegetable crops.Studies were conducted to evaluate the effect of various rates ofhalosulfuron on purple nutsedge tuber production. Single, presprouted purplenutsedge tubers were transplanted into outdoor microplots and treated after6 wk of growth with six rates of halosulfuron (7 to 208 g aiha−1) POST with a nontreated control (NTC). All shoots that hademerged at the time of application were marked with plastic rings; thisallowed for classification of tubers at exhumation of (1) tubers attached toshoots that had emerged by the time of application, (2) tubers attached toshoots that emerged after application, and (3) tubers without an aerialshoot during the study. Seven weeks after application, the tubers in themicroplots were exhumed and tubers were classified, quantified, and theirability to sprout was evaluated. In the NTC, there were 530 total tubers,with a log-logistic regression model describing the tuber population withincreasing halosulfuron rate. The rate of halosulfuron that reduced totaltuber population 50% (I50) was 8 g ha−1. In the NTC, 200 tubers were attachedto shoots that emerged following halosulfuron application, and this class oftubers had an I50 of 19 g ha−1. Viability of tubers with shoots thatemerged following halosulfuron application was 28% at the 52 g ha−1 halosulfuron, suggesting the action of the herbicide mayhave rendered the tuber nonviable after new shoots were produced. The finalclassification of tubers was those that did not have an aerial shoot duringthe study. These were tubers in which apical dominance suppressed shootdevelopment or were likely the most-recent tubers to develop. Of the threeclasses, the tubers without shoots were the most numerous in the NTC, with294 tubers and an I50 of 1 g ha−1. Halosulfuron is an effective herbicidethat not only controls purple nutsedge foliage but also reduces the numberof new tubers produced and overall tuber viability. This could be animportant component to reduce the long-term population density of theweed.