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  • Author or Editor: Glenn Wehtje x
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Adsorption of 14C-labeled oxadiazon was evaluated in three soilless media and a mineral soil at concentrations between 0.1 and 100 mg·kg-1. Adsorption, which was at least 96%, was not influenced by absorbent type (medium vs. soil) or by oxadiazon concentration. However, desorption was greater in the media than in the soil. After five water extractions, 5.4% of the applied oxadiazon was recovered from media, but only 0.4% was recovered from the soil. In the soil and in two of the media, leaching with water failed to displace oxadiazon 2 cm below the surface to which it had been applied. No oxadiazon was detected below 4 cm in the third medium. Oxadiazon is sufficiently adsorbed to resist leaching-based displacement. Oxadiazon is not likely to enter the environment by escaping from treated containers. Chemical name used: 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-di-methylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon).

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Abstract

Postemergence and preemergence control of goosegrass [Eleusine indica (L.) Gaertn.] and large crabgrass [Digitaria sanguinalis (L.) Scop.] were evaluated with clopropoxydim, fenoxaprop-ethyl, xylofop-ethyl, and poppenate-methyl. None of these herbicides was injurious to Rhododendron obtusum ‘Coral Bells’, Ilex crenata ‘Compacta’, Euonymus alatus ‘Compacta’, Juniperus horizontalis ‘Plumosa’, or Thuja occidentalis ‘Pyramidal’ and, depending on rate, provided acceptable grass control. Only xylofop-ethyl at 0.12 kg ha−1 and poppenate-methyl at 1.12 kg·ha−1 consistently provided at least 90% control. Poppenate-methyl also provided preemergence activity for one to six weeks. Chemical names used: (E,E)-2-[l-[[(3-chloro-2-propeny)oxy]imino]butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-eyclohexen-l-one (clopropoxydim); (±)-ethyl 2-[4-[(6-ehloro-2-benzoxazolyl)oxy]phenoxy]propanoate (fenoxapropethyl); 2-[4-[(6-chloro-2-quinoxalinyl)oxy]-phenoxy]propionic acid (xylofop-ethyl); and methyl-3-hydroxy-4[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]-pentanoate (poppenate-methyl).

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Preplant-incorporated, preemergence, and postemergence herbicides were evaluated for yellow nutsedge (Cyperus esculentus L.) control and for phytotoxicity to four container-grown woody plants. Preplant-incorporated or preemergence applications of chlorimuron at 0.07 kg a.i./ha or imazaquin at 1.12 kg a.i./ha provided the greatest control of yellow nutsedge. Imazaquin applied at 0.28, 0.56, 0.84, or 1.12 kg a.i./ha suppressed growth of Rhododendron × `Copperman' azalea and Lagerstroemia indica ×sfauriai `Natchez'. All other herbicides tested were safe on the four woody plants evaluated. Chlorimuron provided the best combination of yellow nutsedge control and tolerance on woody ornamental. Chemical names used: 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid (chlorimuron); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid (imazaquin).

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Various inorganic soil amendments have been promoted as a means of improving the chemical and physical properties of certain soils. To test this hypothesis, a marginally productive soil was supplemented with 20%, 40%, 60%, and 80% (v/v) of either selected inorganic amendments or sand. Amendments consisted of commercially available diatomaceous earth, calcined clay, zeolite, and crystalline SiO2. The soil material was extracted from the argillic horizon of a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludults). Ability of these soil-amendment mixtures to promote `Tifway' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] growth was evaluated under greenhouse conditions, and contrasted to that obtained in nonamended soil. Selected chemical and physical properties that are pertinent to plant growth were also evaluated. The experiment, which was conducted 3×, began with a §60-day period in which both water and nutrients were optimum. This was followed by a 30-day drought. During optimum water and nutrients, no soil-amendment treatment(s) consistently resulted in superior bermudagrass growth compared to soil alone. However, <2% of the bermudagrass tissue that was produced during the drought became green and succulent with the resumption of irrigation in nonamended soil. This percentage was exceeded by all treatments that contained either ≥60% diatomaceous earth (Axis), or ≥40% calcined clay (Profile); and by 100% zeolite (Clinolite) and 100% silica (Green's Choice). Drought-sustaining ability of soil-amendment mixtures was significantly (P < 0.05) correlated with water-holding ability, soil strength, bulk density, and oxygen diffusion rate, but not correlated with either pH or cation exchange capacity (CEC). While certain inorganic amendments did improve the drought-sustaining ability of soil, the amount required was generally ≥40%.

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Abstract

Control of large crabgrass [Digitaria sanguinalis (L.) Scop.] and goosegrass [Eleusine indica (L.) Gaertn.] was evaluated with the preemergence herbicides oryzalin (Surflan), oxyfluorfen (Goal), and metolachlor (Dual) and the postemergence herbicides quizalofop (Assure), fenoxaprop-ethyl (Whip), haloxyfop (Verdict), poppenate-methyl (Trophy), fluazifop-P (Fusilade 2000), and sethoxydim (Poast) when applied alone or in combination. Oryzalin combinations provided maximum preemergence control compared to oxyfluorfen or metolachlor combinations. Greatest preemergence and post-emergence control was obtained with oryzalin or metolachlor applied with poppenate-methyl. Antagonism of preemergence or postemergence control occurred with several combinations of preemergence and postemergence herbicides. In some instances, control was enhanced by using other herbicide combinations. Chemical names used: 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin); 2-chIoro-1-(3-ethoxy-4-ni-trophenoxy)-4-(trifluoromethyl)benzene (oxyfluorfen); 2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(2-methoxy-1-methylethyl) acetamide (metolachlor); ½(±)-2-[4-[(6-chloro-2-quinoxyalinyl)oxy]phenoxy]propanoic acid¼ (quizalofop); (±)-ethyl 2-[4-[(6-chIoro-2-benzoxazolyl) oxy] phenoxy] propanoate (fenoxaprop-ethyl); 2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid (haloxyfop); methyl 3-hydroxy-4-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]-pentanoate (poppenate-methyl); (R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid (fluazifop-P); and 2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio) propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim).

Open Access

Effects of combining labeled rates of halosulfuron (Sandea) and s-metolachlor (Dual Magnum) were evaluated as a preemergence (PRE) application in a randomized complete block designed experiment at the Wiregrass Experiment Station in southeastern Alabama. Treatments were assigned in a factorial arrangement of four levels of halosulfuron (0.0, 0.009, 0.018, and 0.036 lbs. a.i./acre) and six levels of s-metolachlor (0.0, 0.25, 0.50, 0.75, 1.0, and 1.25 lbs. a.i/acre). The purpose of the study was to ascertain possible synergistic effects from combining these two herbicides to control nutsedge at a possible lower cost. Two repetitions were completed in 2005 with data pooled in analysis. Results found no interaction between the halosulfuron and the s-metolachlor and therefore no synergistic affects. Analysis of the main effects revealed that the highest labeled rate of either herbicide gave the highest percent control relative to the nontreated control. Soil activity of halosulfuron in controlling nutsedge has been shown to be less effective than foliar applications. Our own LD90 greenhouse studies confirmed this to be true. We examined four application techniques of halosulfuron (POST both soil and foliar, POST foliar only, POST soil only, and PRE soil only) to determine the LD90. Results revealed that halosulfuron had the lowest LD90 from the treatments with a foliar application. However, some soil activity was observed. Results from field studies indicated that PRE applications of halosulfuron must be at the highest labeled rate to provide effective control. S-metolachlor was equal to halosulfuron on percent control and is lower in cost on a per acre basis.

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