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Open access

J. P. Gilreath

Abstract

Oryzalin and pronamide provided excellent control of cypressvine morningglory (Ipomoea quamoclit L.) when applied 2 or more times at rates of 2.24 kg a.i./ha. When only one application was made, pronamide was superior to oryzalin for morningglory control. Gladiolus (Gladiolus × hortulanus L.) flower spike number, length, number of florets per spike, and number of corms were not affected by either herbicide; however, spike fresh weight and weights of corms and cormels were reduced in plots treated with pronamide. Chemical names used: 4-(diproplyamino)-3, 5-dinitrobenzenesulfonamide (oryzalin); 3,5-dicloro(N-1,1-dimethyl-2-propynyl) benzamide (pronamide).

Open access

J. P. Gilreath

Abstract

Postemergence and preemergence herbicides were evaluated for crop phytotoxicity and weed control in seepage-irrigated ‘Bristol Fairy’ gypsophila (Gypsophila paniculata L.). DCPA, napropamide, pronamide, and oryzalin were severely injurious to gypsophila. Metolachlor, oxyfluorfen, alachlor, and oxadiazon provided varying degrees of weed control and did not reduce plant vigor or yield. Best weed control was provided by two applications of 4.48 kg·ha-1 oxadiazon. Chemical names used: dimethyl tetrachloroterephthalate (DCPA); 2-(napthoxy)-N, N-diethylpropionamide (napropamide); 3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide (pronamide); 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin); 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene (oxyfluorfen); 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide (alachlor); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2(3H)-one (oxadiazon).

Open access

J. P. Gilreath

Abstract

A menu-driven data collection program, “Gather”, was written for a TRS-80 Model 100 (Radio Shack, a division of Tandy Corp., Fort Worth, TX 76102) portable microcomputer (3). This program creates an ASCII (American Standard Code for Information Interchange) (4) data file with each line consisting of the data entry for each observation of a single variable.

Open access

J. P. Gilreath

Abstract

Data collection and analysis are time-consuming processes. Each time data are transcribed, the probability of error increases. Electronic data collection devices are commercially available; however, they are relatively expensive (more than $2000). In addition, they may require programming by the user, or purchase of program instructions in the form of read-only memory (ROM) chips. Many individuals cannot afford to invest in one of these devices. Several lightweight portable computers are now available for under $1000. Among these is one sold by Radio Shack under the trade name TRS 80 Model 100 (Radio Shack, a division of Tandy Corporation, Fort Worth, TX 76102) which can be purchased with different amounts of memory and comes with a phone modem for telecommunications, an RS-232C interface, a text editor, and resident MBASIC (Microsoft Corporation, 10700 Northrup Way, Bellevue, WA 98004) programming language. MBASIC is a relatively common version of BASIC which is available for a large selection of computers. The Model 100 could thus be used for data collection, text preparation, and programming applications in BASIC. Currently, no menu-driven data collection programs are available for the Model 100 or any other portable computer.

Open access

J. P. Gilreath

Abstract

Seventeen herbicide treatments applied pre- and posttransplant were evaluated for toxicity to statice (Limonium sinuata L.) in 2 screening experiments. From these, 6 treatments were selected for further evaluation. Two applications (one pre-transplant followed by one posttransplant over the top) of 1.7 kg/ha alachlor, 4.5 kg/ha oxadiazon, 3.4 kg/ha EPTC, 9.0 kg/ha DCPA, 2.2 kg/ha napropamide, and 2.2 kg/ha oryzalin were evaluated for toxicity to field-grown ‘Midnight Blue’ statice. Oxadiazon, EPTC, and DCPA were not injurious to statice and produced yields of marketable panicles that were comparable to those in the untreated weed-free checks. Alachlor, napropamide, and oryzalin stunted plants and resulted in low panicle yields. Chemical names used: 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide (alachlor); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2(3H)-one (oxadiazon); S-ethyl dipropylthiocarbamate (EPTC); dimethyl tetrachloroterephthalate (DCPA); 2-(naphthoxy)-N,N-diethylpropionamide (napropamide); 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin).

Open access

J. P. Gilreath and S. J. Duranceau

Abstract

Field experiments were conducted to determine the concentration of paraquat residue on black or white polyethylene mulch 0 to 144 hr after application of paraquat at 1.12 kg·ha−1. Effects of eluant from mulch on vigor of 6-week-old tomato (Lycopersicon esculentum Mill. ‘Duke’) plants were also measured. Mulch color had no effect on the rate of photodegradation or on the degree of plant injury. Substantial plant injury was observed from eluants collected from 0 through 96 hr after application of paraquat, with significant injury present until 120 hr after application. After 120 hr, plant vigor was acceptable for their survival, and injury was minimal. Concentration (in the eluant) of paraquat eluted with water from the polyethylene decreased from 275 ppm to <1 ppm from 0 to 144 hr after application, respectively. Significant plant injury was associated with recoverable concentrations >30 ppm of paraquat after 96 hr. Chemical names used: 1,1′-dimethyl-4,4′-bipyridinium salts (paraquat).

Open access

J. P. Gilreath and B. K. Harbaugh

Abstract

One pot study and 2 field experiments were conducted to evaluate the use of ethephon, acifluorfen, endothall, dinoseb, glyphosate, oxyfluorfen, and paraquat as harvesting aids (removal of root and shoot tissue) in caladium (Caladium × hortulanum Birdsey) tuber production. Of these 7 compounds, paraquat and oxyfluorfen showed the most potential with 2 applications at 15-day intervals reducing ‘Canadium’ and ‘Freida Hemple’ caladium root weight as much as 51% and shoot weight up to 90%. No residual effects were observed for these herbicide treatments when tubers were subsequently forced in a greenhouse. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon); [2-chloro-4-(trifluoromethyl)phonoxy]-2-nitrobenzoate (acifluorfen) (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid (endothall); 2-(l-methylpropyl)-4,6-cinitrophenol (dinoseb); N-(phosphonomethyl)glycine (glyphosate); 2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifluormethyl)benzene (oxyfluorfen); (1,1-dimethyl-4,4′-bipyridinium ion (paraquat).

Open access

J. P. Gilreath and B. K. Harbaugh

Abstract

Eight herbicides were evaluated for phytotoxicity to field grown ‘Candidium’ caladiums (Caladium × hortulanum Birdsey) in 1983. The 4 most promising or currently used herbicides were evaluated for weed control and phytotoxicity in 1984. During 1984, 4 applications of 2.24 kg/ha alachlor, 2.24 kg/ha simazine, 1.68 kg/ha oryzalin, and 0.56 kg/ha oxyfluorfen, all in combination with 1 postemergence application of 0.28 kg/ha fluazifop-butyl, were applied to caladiums. Alachlor and oxyfluorfen provided poor weed control and reduced plant vigor, tuber weights, and tuber size in 1984. Simazine provided good weed control, but reduced plant vigor and yield. Oryazlin provided excellent weed control without crop injury. Chemical names used: 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide (alachlor); 6-chloro-N,N’-diethyl-1,3,5-triazine-2,4-diamine (simazine); 4-(dipropylamino)-3,5-dinitrobenzene sulfonamide (oryzalin); 2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene (oxyfluorfen); butyl-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanoate (fluazifop-butyl).

Free access

Timothy N. Motis, Salvadore J. Locascio, and James P. Gilreath

Yellow nutsedge (Cyperus esculentus L.) interference with bell pepper (Capsicum annuum L.) has become an important concern because of the phase-out of methyl bromide as a soil fumigant. The critical period for yellow nutsedge control in pepper was determined in two adjacent experiments (removal and plant-back) conducted twice in separate fields each Spring and Fall 2000 in Gainesville, Fla. In the removal experiment, nutsedge was planted with pepper in all but the full-season (13 weeks) weed-free controls and removed at 1, 3, 5, and 7 weeks after pepper transplanting (WAPT). Full-season weedy control plots in the removal experiment were obtained by never removing nutsedge planted with pepper (0 WAPT). In the plant-back experiment, all but the full-season weed-free controls received nutsedge with nutsedge planted at 0 (full-season weedy control), 1, 3, 5, and 7 WAPT. Sprouted nutsedge tubers were planted at a density of 45 tubers/m2. Results indicated that a nutsedge-free period from 3 to 5 WAPT in spring and 1 to 7 WAPT would prevent >10% yield reductions of large and marketable peppers. Full-season nutsedge interference reduced pepper yields by >70%. When planted with pepper, nutsedge shoots grew taller than pepper plants with nutsedge heights at 5 WAPT up to two times greater in fall than spring. Results indicated that yellow nutsedge control practices should be initiated earlier and continue longer in fall than spring due to faster early-season nutsedge growth in fall than spring.

Free access

James P. Gilreath, Carlene A. Chase, and Salvadore J. Locascio

Drift from pesticides can kill or damage nontarget organisms. In these studies, the effects of sublethal rates of the herbicide glyphosate applied prebloom, at bloom, and postbloom of the first flower cluster were evaluated in tomato (Lycopersicon esculentum Mill.). As rates increased from 1 to 100 g·ha-1, foliar injury and flower and fruit number per plant varied with the stage of development at the time of exposure and the time of evaluation after treatment. Plants treated with 60 and 100 g·ha-1 glyphosate prebloom and at bloom had developed moderate to severe foliar injury by 14 days after treatment, but phytotoxicity to plants treated postbloom was only mild to moderate. Blooms abscised from plants treated with 60 and 100 g·ha-1 glyphosate for several weeks after application and fruit set was reduced. Greatest yield losses occurred following treatment prebloom (just prior to bloom) and at bloom. Plants treated before emergence of flower buds, and more mature plants exposed when first cluster fruit were sizing, yielded better than did those treated just prior to bloom and at bloom. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).