Evaluation of Preemergence and Postemergence Herbicide Systems and Physiological Behavior of CGA-362622 on Purple and Yellow Nutsedge (Cyperus Rotundus L. and C. Esculentus L.).
Evaluation of Preemergence and Postemergence Herbicide Systems and Physiological Behavior of CGA-362622 on Purple and Yellow Nutsedge (Cyperus Rotundus L. and C. Esculentus L.).

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Publisher:

Published: 2002

Total Pages:

ISBN-13:

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Purple and yellow nutsedge are herbaceous perennial weeds that are among the world's worst pests. Nutsedge species are problematic due to their perennial nature, longevity of tubers, and prolific tuber production. Due to the relatively difficulty in reducing purple and yellow nutsedge populations, herbicide-management programs in cropping systems that target nutsedge species need to be developed. Field studies were conducted to evaluate potential reduction in purple and yellow nutsedge populations using sulfentrazone and glyphosate management programs and site-specific management in a tobacco and soybean rotation, as well as using sulfentrazone, glyphosate, and halosulfuron management programs in a soybean and corn rotation. All weed management systems reduced purple nutsedge densities similarly in the tobacco and soybean rotation. Sulfentrazone plus clomazone preplant incorporated (PPI) in tobacco or preemergence (PRE) in glyphosate-resistant (GR) soybean reduced yellow nutsedge densities 82 and 99%, respectively. Postemergence (POST) treatments of glyphosate in GR soybean did not increase yellow nutsedge reductions when sulfentrazone was applied in tobacco or GR soybean. Glyphosate applied on a site-specific basis POST with a light-activated hooded sprayer (LAS) reduced yellow nutsedge populations as effectively as glyphosate POST broadcast treatments in GR soybean. Weed management systems that included sulfentrazone PRE fb the LAS in GR soybean reduced POST herbicide use by at least 86%, compared to broadcast applications. Sulfentrazone plus clomazone PRE alone in GR soybean followed by (fb) nicosulfuron POST in GR corn reduced purple and yellow nutsedge populations by 48 and 85% relative to the nontreated control, respectively. Clomazone PRE in GR soybean fb sequential treatments of glyphosate POST in GR soybean and in GR corn, reduced purple and yellow nutsedge populations equivalent to soybean PRE herbicide programs and other GR corn POST management programs.

Modeling Purple Nutsedge (Cyperus Rotundus L.) Growth
Modeling Purple Nutsedge (Cyperus Rotundus L.) Growth

Author: A. A. L. Amerasinghe

Publisher:

Published: 1992

Total Pages: 310

ISBN-13:

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Purple nutsedge [Cyperus rotundas L.) has been recognized as one of the most troublesome perennial weeds of agricultural lands in tropical and some temperate regions. This research sought to determine the effects of timing of herbicides, shading, and soil moisture on plant population growth and tuber production of purple nutsedge through field and greenhouse experiments. The results of these experiments were used to validate a purple nutsedge population matrix model constructed with observed and reported data. Purple nutsedge control options were evaluated with model simulations. Glyphosate reduced shoot number, tuber number, and tuber viability of purple nutsedge, and the herbicide efficacy was higher when applied from 2 to 4 weeks after shoot emergence as compared to the first 2-week growth period. The more effective period for the herbicide coincided with the tuber initiation phase of purple nutsedge growth. Metolachlor caused only temporary suppression of purple nutsedsge. Sunlight intensity by 30%, 47%, 63%, and 90% caused in successively greater reductions in shoot number, tuber number, leaf area, and total dry weight of purple nutsedge. Shading decreased partitioning of plant biomass into tubers and increased partitioning into leaves. These responses remained essentially the same irrespective of timing of shading from early emergence through the first 4 weeks of plant growth. Depletion of available soil moisture from 25% to 75% also reduced the number and dry weights of shoots and tubers produced. However, proportional biomass allocation to shoots, leaves, and tubers and relative growth and net assimilation rates remained unaltered with soil moisture depletion, suggesting that purple nutsedge is fairly well adapted to low soil moisture levels. The importance of intraspecific competition on population regulation of purple nutsedge was evident from model simulations. Model predictions of maximum population size closely agreed with reported plant and tuber densities of purple nutsedge. Model simulations of proportional changes in population size of purple nutsedge, as influenced by soil moisture depletion or shading, also closely followed the field results. Model simulations indicated that seasonal application of herbicides resulting in 90% shoot kill will provide a successful level of control and that herbicide efficiency will be higher when shoots are killed during the second to fourth week of the growing period than from earlier applications. However, model simulations showed that a better strategy than using a highly effective, short duration herbicide is to provide a moderate level of purple nutsedge control extending through the growing season.