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James P. Gilreath

Abstract

Preemergence herbicides for weed control in field-grown statice [Limonium sinuatum (L.) Mill.], applied pretransplant, with a second posttransplant application over the top of the crop before flowering, were evaluated. DCPA, oxadiazon, and oxyfluorfen generally provided safe, efficacious weed control in the first experiment (1984) and were further evaluated in the second experiment (1985), wherein crop vigor and yield were not reduced. Control of most weeds was good with DCPA, oxadiazon, and oxyfluorfen; however, crabgrass [Digitaria sanguinalis (L.) Scop.] control with oxyfluorfen was inconsistent in both experiments and decreased late in the season. Chemical names used: dimethyl 2,3,5,6-tetrachloro-1,4-benzene-dicarboxylate (DCPA); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (oxyfluorfen).

Open access

James P. Gilreath

Abstract

Postemergence applications of fluazifop-butyl and sethoxydim at rates of 0.28, 0.56, and 0.84 kg a.i./ha provided excellent control of seedling Digitarla ciliaris (Retz.) Koel and Eleusine indica (L.) Gaertn. in achimenes (Achimenes grandiflora Dc. ‘Cascade Violet Night’), impatiens (Impatiens wallerana Hook. f. ‘Elfin Salmon’), marigold (Tagetes erecta L. ‘Yellow Galore’), petunia (Petunia hybrida Hort. Vilm.-Andr. ‘Burgundy’), and salvia (Salvia splendens F. Sellow ex Roem. & Schult. ‘Blaze of Fire’). Herbicide treatment did not affect achimenes rhizome size or weight nor plant vigor, height, or bloom production of impatiens, marigolds, petunias, or salvia. Chemical names used: (±)–2[4–[[5–(trifluoromethyl)2–pyridinyl]oxy]phenoxy]propanoic acid (fluazifop-butyl); 2-[1](ethoxyimino)butyl]propyl]-3-hydroxy-2-cyclohexenl-1-one (sethoxydim).

Free access

Bielinski M. Santos and James P. Gilreath

Among the current methyl bromide alternatives under study, propylene oxide (Propozone) has shown potential to control soilborne diseases, nematodes, and weeds in polyethylene-mulched tomato. However, further research is needed to determine the appropriate application rates to control nutsedge in the crop. Also, the effect of this fumigant on tomato nutrient absorption has not been determined yet. Therefore, field trials were conducted for this purpose in Bradenton, Fla. Tested rates of Propozone were 0, 190, 380, 570, 760, and 950 L·ha–1 and were shank-applied in raised planting beds three weeks before `Florida 47' tomato transplanting. Examined data indicated that there was a rapid decrease in nutsedge density with 570 L·ha–1. For phosphorus (P) and potassium (K) foliar content, there was a linear increase of P concentrations as rate increase, whereas K content increased rapidly after 190 L·ha–1. The highest tomato yields were obtained with 760 and 950 L·ha–1 of Propozone.

Full access

James P. Gilreath and Bielinski M. Santos

Two independent field studies were conducted to determine the efficacy of methyl iodide (MI) formulations and rates on mixed nutsedge [purple nutsedge (Cyperus rotundus) and yellow nutsedge (Cyperus esculentus)] stands and their effects on tomato (Solanum lycopersicum) yields. In both studies, treatments were rates of two formulations of MI + chloropicrin (Pic) at the 98:2 (v/v) and 50:50 (v/v) proportions. In the MI + Pic 98:2 study, the fumigant rates were 0, 100, 125, 150, 175, and 200 lb/acre in Spring 2004 and 0, 125, 150, 175, and 200 lb/acre in Fall 2004. In the MI + Pic 50:50 study, the rates were 0, 200, 250, 300, 350, and 400 lb/acre during both seasons. Additionally, a grower standard was included in each study, which consisted of plots fumigated with methyl bromide (MBr) + Pic 67:33 (v/v) at a rate of 350 lb/acre. Higher rates of MI + Pic 98:2 and 50:50 significantly reduced mixed nutsedge densities and increased relative marketable fruit weight of tomato. Plots fumigated with MBr + Pic were weed-free at the sampling times during both studies. Data from both studies indicated that MI + Pic 98:2 and 50:50 rates of 125 and 200 lb/acre, respectively, consistently provided the highest marketable fruit weights and mixed nutsedge control, which were similar to those obtained in plots treated with MBr + Pic.

Free access

Bielinski M. Santos and James P. Gilreath

Purple nutsedge can easily penetrate polyethylene mulch films. However, there are no reports on possible differences among mulch films. Because of this situation, field trials were conducted in Ruskin and Bradenton, Fla., during 2002 and 2003. In Spring 2002, the treatments were a) no mulch, b) black Pliant High Barrier mulch, and c) green Klerk's Virtually Impermeable Film (VIF). In Spring 2002, the films were a) black Pliant High Barrier, b) black IPM Bromostop, c) metallized Pliant, and d) green Klerk's VIF. The number of nutsedge emerged through the films was determined. No fumigants or herbicides were applied. Results indicated that the Klerk's VIF had the lowest nutsedge densities. No nutsedge control differences were found between the IPM Bromostop and the metallized Pliant films. These differences might be due to the physical properties of the films, including stretching and thickness.

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Bielinski M. Santos and James P. Gilreath

Over the years, efficacy of metam potassium (MK) on purple nutsedge (Cyperus rotundus) control has been inconsistent, in many cases because of a lack of knowledge about application techniques. Therefore, field studies were conducted to determine the effect of water delivery volumes and flow rates on purple nutsedge control with MK, and the influence of MK rates and concentrations on purple nutsedge control. Three separate studies were established for 1) water application volumes and flow rates, 2) MK application rates and concentrations, and 3) MK concentration levels. For the water application volumes and flow rate trials, a single MK rate of 60 gal/acre was injected with either 1 or 2 acre-inch/acre (27,154 or 54,308 gal/acre) of water. The water flow rates were 0.30, 0.45, and 0.60 gal/100 ft of row per minute within each water volume. An nontreated control was included. In the application rate and concentrations studies, treatments were a nontreated control, 30 gal/acre applied with 0.5 acre-inch/acre of water (≈3000 ppm), 60 gal/acre applied with either 0.5 or 1 acre-inch/acre of water (≈6000 and 3000 ppm), 120 gal/acre applied with either 1 or 2 acre-inch/acre of water (≈6000 and 3000 ppm), and 240 gal/acre applied with 2 acre-inch/acre of water (≈6000 ppm). In the MK concentration trials, 0, 2000, 3000, 4000, 5000, and 6000 ppm were tested. Results indicated that neither water volumes nor flow rates used for MK application had a significant impact on purple nutsedge control at 10 weeks after treatment (WAT). However, there was a significant effect of the combinations of MK rates and water delivery volumes on purple nutsedge densities at 4 and 15 WAT. Similarly, MK concentrations obtained from a single application rate resulted in improved purple nutsedge control up to 10 WAT, reducing densities to less than 5 plants/ft2 with 6000 ppm of MK.

Full access

Bielinski M. Santos and James P. Gilreath

A 2-year field study was conducted in two locations in the Dominican Republic to determine the influence of various support systems and nitrogen fertilization programs on passion fruit (Passiflora edulis var. flavicarpa) yield and economic returns. Three trellis systems were used: 1) single line, where a single wire was placed along the planting rows at 2 m high; 2) double lines, where two wires were established along the planting rows at 2 and 1 m high, respectively; and 3) crossed lines, with wires at 2 m high, allowing the vines to grow both along and across the planting rows. Nitrogen (N) fertilization rates were 13, 26, and 52 g/plant of N every 20 days. Plants trained with the single- and double-line support systems combined with 52 g/plant of N had higher marketable yield and had the lowest proportion of non-marketable fruit/plant per year. Partial budget analysis indicated that the single-line support system had a marginal return rate of 36% compared to the double-line support system.

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

Camille E. Esmel, Bielinski M. Santos, and James P. Gilreath

Nitrogen (N) is the most growth-limiting for vegetable production in sandy soils. In Florida, current recommendations for preplanting N applications (100 lb/acre of N) in `Crookneck' summer squash (Cucurbita pepo) differ from those used by the growers (>200 lb/acre). Therefore, two field studies were conducted in Ruskin and Balm, Fla., to examine the effect of 50, 100, 150, 200, 250, and 300 lb/acre of N on summer squash growth and yield. Variables collected during this study were plant vigor (0–10 scale, where 0 = dead plant) at 3 and 7 weeks after planting (WAP), petiole sap nitrate-nitrogen (NO3-N) at 4 and 8 WAS, and marketable yield starting on 4 WAS (13 and 10 harvests in Ruskin and Balm, respectively). In Ruskin, plant vigor increased linearly with N rates, whereas there was no significant N effect in Balm. No differences in petiole sap NO3-N were observed in either location. In Ruskin, there was a rapid marketable yield increase (§25%) between 50 and 100 lb/acre of N, followed by no change afterwards. In contrast, there was no yield response in Balm. In the latter location, no crop had been established in the previous 3 years, enabling the soil to maximize its organic N accumulation (>40 lb/acre organic-N), whereas in Ruskin the experimental location had been continuously planted during the last three seasons (§25 lb/acre organic-N). The data demonstrated that organic N is an important source of the nutrient to complement preplant applications in summer squash.

Free access

Bielinski M. Santos, James P. Gilreath, and Timothy N. Motis

Two field trials were conducted in Bradenton, Fla., to determine the effect of reduced methyl bromide plus chloropicrin (MBr + Pic 67:33 v/v) rates applied under two types of virtually impermeable films (VIF) on nutsedges (Cyperus spp.) and stunt nematode (Tylenchorhynchus spp.) control, and `Capistrano' bell pepper (Capsicum annuum) crop yield. MBr + Pic rates were 0, 88, 175, and 350 lb/acre. Mulch types were low-density polyethylene (LDPE) mulch, Hytibar VIF, and Bromostop VIF. Results showed that there were no differences on weed and nematode control, and bell pepper fruit yield between the two types of VIF. Two exponential models characterized the nutsedge responses to MBr + Pic rates with LDPE mulch and VIF, with weed densities declining as MBr + Pic rates increased. Reducing MBr + Pic rates by one-half (175 lb/acre) under VIF provided similar nutsedge control as the full-rate (350 lb/acre) with LDPE mulch. Similar results were observed with stunt nematode, where the most effective control occurred with VIF. Bell pepper yield with LDPE mulch responded linearly to increased MBr + Pic rates. However, a logarithmic model described the response of pepper yields to the fumigant rates under VIF. The application rate of this fumigant could be effectively reduced to 25% of the commercial rate (350 lb/acre) under either VIF, without causing significant bell pepper yield losses.