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Julian Mendel, Christina Burns, Beatrice Kallifatidis, Edward Evans, Jonathan Crane, Kenneth G. Furton, and DeEtta Mills

fungicide presently approved capable of curing an infected tree, although propiconazole has been shown to provide around 12 months of protection when injected or infused prophylactically into trees ( Mayfield et al., 2008 ; Ploetz et al., 2017d ). The

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Hazel Y. Wetzstein, Elizabeth A. Richardson, and Yi He

Propiconazole, a triazole fungicide, has been reported to inhibit leaf expansion in pecan [Carya illinoensis (Wangenh.) K. Koch] trees when applied under field conditions. This study was conducted to determine the effect of propiconazole on pecan leaf morphology and structure using light and transmission electron microscopy. Mature pecan trees were sprayed once or three times per week from budbreak to pollen maturity. Fungicide sprays resulted in significantly reduced leaf area. Compared to controls, leaves from propiconazole-treated shoots had alterations in cell arrangement characterized by more tightly packed palisade parenchyma cells with fewer intercellular spaces; neither leaf thickness nor palisade or spongy layer thickness were affected. Propiconazole caused modifications in the chloroplasts, with a tendency for internal membranes to be less defined, and for thylakiods to exhibit less stacking. The extent of structural changes was related to fungicide dosage. Results show that propiconazole applications during leaf development can inhibit leaf expansion and modify cellular organization of the mesophyll cells. Chemical name used: 1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl] methyl]-1H-1,2,4-triazole (propiconazole).

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Xunzhong Zhang, E.H. Ervin, and R.E. Schmidt

Decline of sod quality during the transportation, storage, and transplant stages of sale is a primary economic concern of sod producers. However, the mechanisms of extending sod quality during storage, transportation, and transplantation remain unclear. This study was conducted to investigate the influences of selected plant metabolic enhancers (PMEs) seaweed (Ascophyllum nodosum Jol.) extract (SWE), humic acid [93% a.i. (HA)], and propiconazole (PPC), on sod tolerance to stress during storage and posttransplant root growth of tall fescue (Festuca arundinacea Schreb.) sod. The SWE + HA, and PPC were applied alone, or in a combination, to tall fescue 2 weeks before harvest. Photochemical efficiency (PE) of photosystem II was measured immediately before harvest. The harvested sod was subjected to high temperature stress (40 °C) for 72 or 96 hours. The heated sod was replanted in the field and posttransplant injury and root strength were determined. On average over 1999 and 2000, application of SWE (50 mg·m-2) + HA (150 mg·m-2), PPC (0.30 mL·m-2), and a combination of SWE + HA with PPC (0.15 mL·m-2), enhanced PE of preharvest sod by 8.5%, 9.1%, and 11.2%, respectively, and increased posttransplant rooting by 20.6%, 34.6%, and 20.2%, respectively. All PME treatments reduced visual injury except SWE + HA and SWE + HA + PPC in 1999. Extension of heat duration from 72 to 96 hours caused significantly more injury to the sod and reduced posttransplant rooting by 22.9% averaged over 2 years. The data suggest that foliar application of SWE + HA, PPC alone, or in a combination with SWE + HA, may reduce shipment heat injury and improve posttransplant rooting and quality of tall fescue sod. Chemical name used: 1-(2-(2,4-dichloropheny)-4-propyl-1,3-dioxolan-2yl)methyl-1-H-1,2,4-triazole [propiconazole (PPC)].

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E.H. Ervin, Xunzhong Zhang, J.M. Goatley Jr., and S.D. Askew

Creeping bentgrass (Agrostis stolonifera) is used extensively on temperate zone golf course greens, tees, and fairways, but often performs poorly in shade. Previous research has indicated that sequential applications of gibberellic acid (GA) inhibiting plant growth regulators (PGRs) such as trinexapac-ethyl (TE) increase cool-season turfgrass performance in 70-90% shade. This research was conducted to: 1) confirm appropriate TE application rates and frequencies for maintaining `Penncross' creeping bentgrass in dense shade in the mid-Atlantic region of the U.S.; 2) determine the efficacy of other PGRs, biostimulants, and iron (Fe); and 3) assess whether the addition of a biostimulant with TE would have additive, synergistic, or negative effects. The other compounds tested against TE and the control were: propiconazole (PPC), iron sulfate, CPR (a seaweed and iron containing biostimulant), and a generic seaweed extract (SWE) (Ascophyllum nodosum) plus humic acid (HA) combination. These treatments were applied to 88% shaded bentgrass every 14 days from May or June through October in 2001 and 2002, with turf quality, leaf color, root strength, photochemical efficiency, and antioxidant enzyme superoxide dismutase (SOD) activity being determined. While the quality of control plots fell below a commercially acceptable level by the second month of the trial, repeated foliar TE application provided 33% to 44% better quality throughout the experiment. Propiconazole resulted in 13% to 17% better quality through September of each year. Trinexapac-ethyl and PPC resulted in darker leaf color and increased mid-trial root strength by 27% and 29%, respectively. Canopy photochemical efficiency and leaf SOD activity were also increased due to TE in August of both years. Treatment with Fe, CPR, or SWE+HA did not have an effect on quality, root strength, SOD, or photochemical efficiency, but periodic increases in color were observed. The addition of CPR to TE in 2002 provided results that were not different from those of TE-alone. This and previous studies indicate that restricting leaf elongation with anti-GA PGRs is of primary importance for improving shade tolerance, while treatments that increase leaf color or chlorophyll levels without restricting leaf elongation are relatively ineffective.

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Xunzhong Zhang and R.E. Schmidt

Superoxide dismutase (SOD) activity is closely associated with stress tolerance of creeping bentgrass [Agrostis stoloniferous L. var. palustris (Huds.) Farw (syn. A. palustris Huds.)]. This study was conducted to investigate the influence of two plant growth regulators (PGRs) on the endogenous antioxidant SOD level and photochemical activity in `Penncross' creeping bentgrass grown under two fertilizer regimes. Mature `Penncross' was treated monthly with TE at 0.44 g a.i./100 m2 and PPC at 3.37 g a.i./100 m2 from May through November at the Virginia Tech Turfgrass Research Center, Blacksburg, Va. Foliar application of TE and PPC increased SOD activity, photochemical activity, and Fm730/Fm690 ratio of creeping bentgrass under the two fertilization regimes as well as when the grass was exposed to a low soil moisture environment. TE reduced clipping weight consistently regardless of the fertilization regime. In contrast, PPC increased clipping weight slightly. Both TE and PPC significantly reduced Dollar spot disease (Sclerotinia homoeocarpa Bennett) under both high and low fertilization regimes. No significant fertilization × PGR interactions for SOD, photochemical activity of PS II, and Fm730/Fm690 were observed in well-watered or drought stressed bentgrass. Improvement in stress tolerance of creeping bentgrass by the PGRs appears to be associated partially with an increase of endogenous SOD activity. Chemical names used: trinexapac-ethyl (TE); propiconazole (PPC).

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Nathaniel A. Mitkowski and Arielle Chaves

moderate risk for resistance development ( FRAC, 2012 ). Active ingredients that are currently registered for use in the United States include: fenarimol, myclobutanil, metconazole, propiconazole, tebuconazole, triadimefon, and triticonazole (fenarimol use

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Mary C. Koelsch, Janet C. Cole, and Sharon L. von Broembsen

Common periwinkle and `Bowles' periwinkle production has declined in the southern United States due to foliar diseases caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz. and Phoma exigua Desmaz. var. inoxydabilis Boerema & Vegh in Vegh et al. Our study determined whether several labeled and experimental fungicides could control pathogens causing foliar diseases in common periwinkle in vitro and outdoors during two consecutive summers. Five concentrations of each of eight fungicides were used to test inhibition of mycelial growth of P. exigua var. inoxydabilis and two isolates of C. gloeosporioides on fungicide-amended agar. All concentrations of propiconazole inhibited growth of P. exigua var. inoxydabilis (100%) and both isolates of C. gloeosporioides (>96%). Cyproconazole completely inhibited mycelial growth of P. exigua var. inoxydabilis. Thiophanate methyl/mancozeb partially inhibited growth of C. gloeosporioides (50%). In outdoor trials, plants were sprayed weekly with the following fungicides and rates (in g a.i./liter): thiophanate methyl/mancozeb, 1.35; propiconazole, 0.14; thiophanate methyl, 0.84; triforine, 0.27; cyproconazole, 0.08; triforine–CC 17461, 0.27; or CGA 173506, 0.90. Thiophanate methyl/mancozeb was most effective at reducing foliar necrosis during both seasons. Shoot dry weights of plants treated with thiophanate methyl/mancozeb were significantly higher at the end of each growing season than those of plants treated with the other fungicides or the nontreated control plants. Chemical names used: dimethyl [(1,2-phenylene)-bis (iminocarbonothioyl)] bis [carbamate] and a combination of zinc ion and manganese ethylenebisdithiocarbamate (thiophanate methyl/mancozeb); 1-[2-(2′,4′-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl-methyl]-1H-1,2,4-triazole (propiconazole); dimethyl [(1,2-phenylene)-bis (iminocarbonothioyl)] bis [carbamate] (thiophanate methyl); N,N′-[1,4-piperazinediylbis (2,2,2-trichloroethylidene)] bis [formamide] (triforine); 2-(4-chlorophenyl)-1-(1H-1,2,4-triazol-l-yl)-butan-2-ol (cyproconazole); N,N′-[1,4-piperazinediylbis (2,2,2-trichloroethylidene)] bis [formamide] with micro emulsion (triforine–CC 17461); 4-(2-2-difluoro-1,3-benzodioxol-4-yl) pyrrole-3-carbonitrile (CGA 173506).

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Kathryn C. Taylor and Parshall B. Bush

To discern how the packing process influences pesticide residue loads on peach (Prunus persica L. Batsch) fruit; postharvest, post hydrocooled, and post brushed fruit were assessed for levels of several pesticides. The packing house process reduced pesticide residue levels on fresh peaches to levels that were generally below detection limits of our assays in 1998. Carbaryl and captan residues from field packed fruit were 32.2× and 21.9×, respectively, of that found in the peel of fruit processed in the packing house in 1998. Carbaryl levels were not reduced by hydrocooling but postharvest brushing reduced pesticide residues up to 94% in fruit peel. Across processing operations and cultivars assessed in 1999, hydrocooling, hydrocooling plus brushing, and brushing alone removed 37%, 62%, and 53%, respectively, of the encapsulated methyl parathion residues from fruit peel. Hydrocooling had the greatest impact on phosmet removal from peel, reducing levels by 72.5%. After hydrocooling, phosmet was 5.7× following brushing in one-half of the subsequent samples. This increase occurred at all three farms, suggesting that periodic cleaning of brushes may be necessary to prevent later contamination of peach peel with pesticides. In the only example in which propiconazole residue remained on peaches at picking, it was removed most effectively (69%) by the brushing operation. Nearly 31% of the propiconazole was removed in the hydrocooler. The packing process before shipment to retail outlets was generally effective in the removal of pesticides that may be present on peel at the time of harvest. Assessment of pesticide residue levels in peach flesh was uniformly below the levels of detection in our assays, suggesting that the classes of pesticide analyzed in peaches were not transepidermal.

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Lambert B. McCarty, Leon T. Lucas, and Joseph M. DiPaola

Spring dead spot (SDS) [Gaeumannomyces graminis (Sacc.) von Arx & D. Olivier var. graminis Walker] is a serious disease of bermudagrass [Cynodon dactylon (L.) Pers.] throughout much of the southern United States and is believed to be at least partially influenced by the previous year's turfgrass management practices. Research was performed to: a) determine the efficacy of selected fungicide control measures; and b) determine the influence of N and K nutrient regimes on the expression of SDS symptoms in Tifway bermudagrass (C. dactylon x C. transvaalensis Burtt-Davy). Averaged over two sites in 2 years, a 72% reduction in SDS followed a fall application of benomyl at 12 kg·ha. Fenarimol applied at three rates (1.5, 2.3, and 3.0 kg·ha) on three fall dates reduced SDS by a combined average of 66%. A single application of propiconazole (2.5 kg·ha) reduced disease by an average of 56%. Application of N (98 kg·ha) in late fall increased SDS 128% in one test location. Application of potassium sulfate (269 kg K/ha) in late fall resulted in an average increase in SDS expression of 89% the following spring over all experiments. Turf managers with severe SDS should minimize heavy late-fall K applications and possibly use benomyl, fenarimol, or propiconazole for disease suppression. Chemical names used: α -(2-chlorophenyl)α -(4-chlorophenyl)-S-pyrimidinemethanol (fenarimol); [methyl 1(butylcarbamoyl)-2-benzimidazolecarbamate] (benomyl); 1-[[2-(2,4-dichlorophenyl)-4propyl-1,3-dioxolan-2-yl]methyl]--1H-1,2,4-triazole (propiconazole).

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John E. Kaminski and Michael A. Fidanza

Spraying Systems (Wheaton, IL). All nozzles were used to apply fungicides with an acropetal penetrant mode of activity (propiconazole; Banner MAXX; Syngenta Professional Products, Greensboro, NC), a contact mode of activity (chlorothalonil; Daconil