Masters Theses
Date of Award
12-1983
Degree Type
Thesis
Degree Name
Master of Science
Major
Plant, Soil and Environmental Sciences
Major Professor
Robert M. Hayes
Committee Members
Elmer L. Ashburn, Larry S. Jeffery
Abstract
Sicklepod (Cassia obtusifolia L.) is a very difficult weed to control. It is not known whether sicklepod can be more effectively controlled by herbicides used in corn (Zea mays L.) those used in cotton (Gossypium hirsutum L.) or those used in soybeans [Glycine max (L.) Merr.]. Research was conducted to evaluate the relative response of sicklepod to several preemergence herbicides used for broadleaf weed control in corn, cotton or soybeans. Residual activity of these herbicides was also determined to discern possible carryover injury to rotational crops. Experiments were conducted at one location in 1982 and two locations in 1983 to evaluate sicklepod response to atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl]amino]-2-methylpropionitrile}, simazine [2-chloro-4,6-bis(ethylamino)-s-triazine], fluometuron [1,I-dimethyl-3-(α,α,aα,-trifluoro-m-tolyl)urea], diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], norflurazon [4-chloro-5-(methylamino)-2-(α,α,α,-trifluoro-m-tolyl)-3(2H)-pyridazinone], and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one]. Residual activity was determined using both field and greenhouse bioassays. The order of herbicidal effectiveness for sicklepod control among the herbicides commonly used in corn was: atrazine > simazine > cyanazine. The order of herbicide effectiveness for the herbicides commonly used in cotton was: fluometuron > diuron = norflurazon > cyanazine. Of the herbicide treatments available for use in soybeans. a single preemergence application of metribuzin was not as effective as the metribuzin system which consists of a preemergence application of alachlor [2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide] plus metribuzin followed by toxaphene (chlorinated camphene, 67 to 69% chlorine) plus crop oil early postemergence followed by metribuzin plus 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] applied late postemergence. The only treatments that consistently provided season long control were atrazine at 4.48 kg ai/ha, atrazine at 3.36 kg ai/ha and atrazine plus simazine at 2.24 plus 1.12 kg ai/ha. Alfalfa (Medicago sativa L.), crimson clover (Trifolium incarnatum L.), and wheat (Triticum aestivum L.) were susceptible to residual injury from the highest rate of atrazine. Wheat was more susceptible to norflurazon residual injury than the other rotational crops. Vetch (Vicia villosa Roth.) was the most tolerant crop tested in regard to residual injury from any of the herbicides studied. In the greenhouse, cucumbers (Cucumis sativus L.) were more susceptible to residual herbicide injury than the cover crops in the field. Where little or no injury to cucumbers was observed from residues in soil samples taken from treated field plots, no residual injury to cover crops was observed in the field. If corn is to be grown on an area infested with sicklepod, at least 3.36 kg ai/ha of atrazine or a herbicide combination containing at least 2.24 kg ai/ha atrazine will be necessary to provide acceptable sicklepod control. A higher potential for residual injury to subsequent crops exists as atrazine rates are increased. If cotton is to be grown, fluometuron at 1.68 kg ai/ha provides the best control of sicklepod; however, subsequent postemergence herbicide applications or other methods of weed control must be employed to give adequate season long control. Metribuzin at 0.56 kg ai/ha provides excellent control of sicklepod for 2 to 3 weeks in soybeans, but for season long control the metribuzin system should be used. There was no residual injury to cover crops from these soybean treatments. Land infested with sicklepod can be more economically and effectively managed if corn is grown rather than cotton or soybeans.
Recommended Citation
Burch, John N., "Relative response of sicklepod to and residual activity of some preemergence herbicides. " Master's Thesis, University of Tennessee, 1983.
https://trace.tennessee.edu/utk_gradthes/7564