Institution:University of Georgia Research Foundation, Inc.
Region:Southeast (GA, FL, AL)
Project Fiscal Year:2015
Report Received Date:
Project NPB Budget:$50,000
Weeds exploit underutilized space, causing economic losses in cropping systems. Weed management tactics alter that underutilized space until the crop can mature and efficiently use that space. One tactic is to reduce the weed propagules (e.g. seeds and tubers) that persist quiescently in the soil, including minimizing production and addition of new propagules to the soil. Purple nutsedge is a problematic weed in peanut, persisting between growing seasons as tubers in the soil. Imazapic (Cadre) is a peanut herbicide often used in Georgia for control of purple nutsedge. The objective of these experiments was to evaluate the effect of various rates of imazapic on purple nutsedge tuber production. Single pre-sprouted purple nutsedge tubers were transplanted into outdoor plots and treated after six weeks of growth with six rates of imazapic (0.25 to 8 oz/acre) POST and a nontreated control. All shoots emerged at the time of application were marked with plastic rings; this allowed for classification of tubers at exhumation of l) 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 wk after application, the tubers in the plots were exhumed, tubers classified, quantified, and ability to sprout evaluated. In the nontreated control, there were 544 total tubers, with a log-logistic regression model describing the declining tuber population with increasing imazapic rate. The rate of imazapic that reduced total tuber population 50% (Iso) was 2 oz/acre. In the nontreated control, there were 161 tubers attached to shoots that emerged, as when compared to plots that received an imazapic application that had an lso = 3.4 oz/acre. Viability of these tubers was 44% at 4 oz/ac, suggesting the action of the herbicide may have rendered the tuber nonviable after new shoots were produced. The final classification of tubers included those that did not have an aerial shoot during the study. These were tubers in which apical dominance suppressed shoot development or were likely the most recent tubers to develop. Of the three classes, the tubers without shoots were the most numerous in the nontreated control, with 358 tubers, and an lso = 1 oz/acre. Imazapic controls purple nutsedge foliage, but also reduces the number of new tubers produced and overall tuber viability and is a valuable tool in management of the long-term population densit of this weed in eanut.