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M.L. Elliott

The growth responses of 10 Rhizoctonia zeae isolates, obtained from turfgrasses in Florida and Ohio, to four temperatures (20, 25, 30, and 35 °C) and seven fungicides at four concentrations (0, 1, 10 and 100 μg·mL-1 a.i.) were compared. Greenhouse pathogenicity tests were conducted using hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy]. Optimal temperature for growth for all isolates was 30 °C. Growth of R. zeae isolates from both geographic locations was severely limited (>75%) at 20 °C. All R. zeae isolates were insensitive to the benzimidazole fungicides, benomyl and thiophanate methyl. Their sensitivities to iprodione, mancozeb, and quinotzene fungicides were similar. The Florida isolates were more sensitive to chlorothalonil, and the Ohio isolates to thiram. All isolates were pathogenic to hybrid bermudagrass. Chemical names used: methyl 1-(butylcarbamoly)-2-benzimidazolecarbamate (benomyl); dimethyl 4,4′-O-phenylene bis(3-thioallophanate) (thiophanate methyl); pentachloronitrobenzene (quintozene); 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidinecarboxamide (iprodione); tetrachloroisophtalonitrile (chlorothalonil); tetramethylthiuram disulfide (thiram); manganese ethylenebisdithiocarbamate (mancozeb).

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M.L. Elliott

Eight demethylation inhibiting (DMI) fungicides were applied at two rates to `Tifgreen' bermudagrass [Cynodon dactylon (L.) Pers. ×x C. transvaalensis Burtt-Davy] to determine if DMI fungicides would produce a plant growth regulation effect on healthy bermudagrass. After three applications at 28- to 30-day intervals, compared to the control, both rates of cyproconazole, bromuconazole, propiconazole and triadimefon and the high rate of myclobutanil significantly decreased turfgrass quality on at least one evaluation date in each year of the study. The low rate of myclobutanil and both rates of tebuconazole and fenbuconazole did not adversely effect turfgrass quality in either year. For both rates of fenarimol, there was only one date during both years of the study when the turfgrass quality was significantly lower than the control. These results demonstrate the wide range of physiological activity the DMI fungicides can have on bermudagrass.

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M.L. Elliott and M. Prevatte

Petroleum and vegetable oil hydraulic fluids were spread on `Tifgreen' bermudagrass at three volumes (125, 250, and 500 ml) and three temperatures (27, 49, and 94C) to simulate a turfgrass equipment leak. Initial damage, recovery, and effects for a 1-year period were compared among treatments. All hydraulic fluid treatments resulted in 100% leaf necrosis within 10 days of application. Turfgrass recovery was influenced primarily by the fluid volume. After recovery, only plots treated with petroleum hydraulic fluid were periodically chlorotic, resulting in lower turfgrass quality. Long-term negative effects of hydraulic leaks from golf course equipment may be reduced by using vegetable oil hydraulic fluid.

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M.L. Elliott and M. Prevatte

Three bone products (meat and bone meal, steamed bone meal, and bone chips) were compared to a water-soluble P source (monocalcium phosphate) for P availability and enhancement of tomato shoot growth. All bone products were finely ground to pass through a 40-mesh sieve. The products were added to a phosphorus-deficient greenhouse growing medium based on their P concentration with P at 50, 100, 200, and 400 mg·kg−1. Meat and bone meal produced the least shoot growth in 1992, but all products were similar in 1993. Growth peaked with P at 111 mg·kg−1 in 1992, but in 1993, P at 50 mg·kg−1 was sufficient. Shoot P uptake was in direct proportion to P availability in the soil mix, monocalcium phosphate having the highest shoot P content. Although bone products affected N, Ca, Zn, and Mn content in shoots, the magnitudes of differences were minor and inconsistent from 1992 to 1993. Major consideration for using a bone product are its relative cost of P, fineness of grind, and CaCO3 equivalent.

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M.L. Elliott and M. Prevatte

Eco, Milorganite, Ringer, and Sustane natural organic fertilizers, alone or combined with the synthetic organic fertilizer isobutylidene diurea (IBDU), were compared with IBDU alone for their effect on a `Tifdwarf' hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] golf course putting green. Over the 2-year study period, no consistent differences were observed among the fertilizer treatments on the turfgrass growth parameters of quality, clipping weights, or root weights.

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M.L. Elliott, E.A. Guertal and H.D. Skipper

The rhizospheres of creeping bentgrass (Agrostis palustris Huds.) and hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) putting greens were sampled quarterly for 4 years. Six bacterial groups, including total aerobic bacteria, fluorescent pseudomonads, actinomycetes, Gram-negative bacteria, Gram-positive bacteria, and heat-tolerant bacteria, were enumerated. The putting greens were located in four geographic locations (bentgrass in Alabama and North Carolina; bermudagrass in Florida and South Carolina) and were maintained according to local maintenance practices. Significant effects were observed for sampling date, turfgrass species and location, with most variation due to either turfgrass species or location. Bentgrass roots had significantly greater numbers of fluorescent pseudomonads than bermudagrass roots, while bermudagrass roots had significantly greater numbers of Gram-positive bacteria, actinomycetes and heat-tolerant bacteria. The North Carolina or South Carolina locations always had the greatest number of bacteria in each bacterial group. For most sampling dates in all four locations and both turfgrass species, there was a minimum, per gram dry root, of 107 CFUs enumerated on the total aerobic bacterial medium and a minimum of 105 CFUs enumerated on the actinomycete bacterial medium. Thus, it appears that in the southeastern U.S. there are large numbers of culturable bacteria in putting green rhizospheres that are relatively stable over time and geographic location.

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T.K. Broschat, D.R. Sandrock, M.L. Elliott and E.F. Gilman

In a series of three experiments, st. augustinegrass (Stenotaphrum secundatum ‘Floratam’), areca palm (Dypsis lutescens), canna (Canna × generalis ‘Richard Wallace’), pentas (Pentas lanceolata), allamanda (Allamanda cathartica ‘Hendersoni’), and nandina (Nandina domestica) were grown on highly leached sand soils in two locations in Florida. They were fertilized with typical turfgrass fertilizers having high nitrogen (N)-to-potassium (K) ratios and no magnesium (Mg), or several types of landscape palm fertilizers having low N:K ratios and 100% of their N, K, and Mg in controlled release form. St. augustinegrass, pentas, nandina, and allamanda visual quality were similar for all fertilizer types tested. However, cannas and areca palms had higher visual qualities when fertilized with an 8N–0.9P–10.0K–4Mg palm fertilizer than with higher N:K ratio turf fertilizers. High N:K turf fertilizers resulted in K deficiency severity equivalent to that of unfertilized controls and Mg deficiency that was more severe than unfertilized areca palms.