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D.A. Rosenberger, T.L. Robinson, J.R. Schupp, C.A. Engle-Ahlers, and F.W. Meyer

Effects of three sterol-demethylation inhibiting (DMI) fungicides and a contact fungicide were compared over two years at each of two locations to determine if fungicide treatments had differential effects on productivity, fruit size and shape, or gross returns for `Empire' apples (Malus ×domestica Borkh.). Treatments were applied four to five times per year during the primary apple scab season. Effects of treatments were assessed by comparing fruit set efficiencies, number of fruit per tree, total harvested fruit weight, and fruit length: diameter ratios at harvest. No significant differences were noted among individual treatments in any of the four trials. However, when treatments were contrasted by grouping individual treatments, significantly larger fruit size was noted for triflumizole treatments vs. combined fenarimol and myclobutanil treatments in one of the four trials and for captan or mancozeb compared to fenarimol and myclobutanil treatments in two trials. None of the DMI fungicides compared in these trials had any consistent adverse affect on fruit size, total yield, or estimated gross return per hectare. We conclude that the plant growth regulator effects of DMI fungicides are inconsistent and are unlikely to have significant economic impact on commercial apple production.

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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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Christian A. Wyenandt, Nancy Maxwell, and Daniel L. Ward

Americas, Burr Ridge, IL) (FRAC codes M3 + M1); 2) standard program: 3.5 L·ha −1 chlorothalonil (Bravo WeatherStik; Syngenta Crop Protection, Greensboro, NC) + 0.35 kg·ha −1 myclobutanil (Nova 40WP; Dow AgroSciences, Indianapolis, IN) (FRAC codes M5 + 3

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Timothy Coolong and Kenneth Seebold

/acre on a 10-d schedule (8 Aug., 19 Aug., 30 Aug., and 11 Sept. 2009). The high-input program in 2009 consisted of applying myclobutanil (Nova 40W; Dow AgroSciences, Indianapolis, IN) applied at a rate of 2 oz/acre alternating with chlorothalonil (1.5 lb

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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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H.B. Pemberton, G.L. Philley, and W.E. Roberson

Plants of Rosa L. `Peace' were field planted in Feb. 1995 in order to test black spot (Diplocarpon rosae Wolf) control efficacy of several compounds. Plants were protected from fungal infection by black spot with weekly sprays of chlorothalonil (Daconil) from 5 Apr. to 8 June 1995 to allow plant establishment. Spray treatments for efficacy testing were started on 23 June and ended on 1 Nov. 1995. All plants were uniformly weeded, fertilized, and irrigated as needed for the duration of the experiment. Plants were rated for defoliation and disease development on 18 July, 1 Sept., and 10 Nov. 1995. A wettable granular formulation of cyproconazole (Sentinel) controlled black spot significantly better when a surfactant, Latron B-1956, was added to the spray solution at 0.5 mL·L–1. Differences between treatments with and without surfactant were greater at lower rates vs. higher rates of cyproconazole. The most effective Sentinel rates with the surfactant were 0.13 g·L–1 applied every 14 days or 0.26 g·L–1 every 21 days. A formulated combination of chlorothalonil and thiophanate methyl (ConSyst) controlled black spot on a 7-day interval at 1.2 g·L–1, but not when applied at 1.8 g·L–1 every 14 days. Control was no better than the standard mancozeb (Dithane) treatment. Neem oil (NeemGard) was not effective on the 14-day schedule tested. Tank mixing neem oil with chlorothalonil or thiophanate methyl (Domain) did not significantly improve control. Neither myclobutanil (Systane) or a formulated combination of mancozeb and myclobutanil (RH 0611) was effective in controlling black spot.

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Weiguang Yi, S. Edward Law, and Hazel Y. Wetzstein

In almond [Prunis dulcis (Mill.) D.A. Webb.], fungicide sprays are required to prevent blossom blight, which can infect open flowers. Numerous studies have reported detrimental effects of agrochemical sprays on pollination, fruit set, and yield in tree fruit crops. However, effects of fungicides on pollen germination and growth in almond are little known, particularly those from recently developed active ingredients. In this study we evaluated the effects of commercial formulations of 10 fungicides on pollen germination and tube growth in almond using in vitro assays. Assays conducted at 1/100 recommended field rates (RFR) were effective in delineating differences in almond pollen sensitivity to different fungicides. Captan and azoxystrobin were the most inhibitory, with germination percentages of less than 1% of the no-fungicide control. Germination was not significantly affected by propiconazole and benomyl. Intermediate inhibitory effects on pollen germination were observed with ziram, cyprodinil, maneb, thiophanate-methyl, iprodione, and myclobutanil. In contrast to germination, tube growth was less affected by the presence of fungicide. In pollen that germinated, tube elongation was the same as in controls in five of 10 of the fungicides evaluated. Nonetheless, azoxystrobin and captan reduced tube elongation by ≈90%. Some fungicide treatments also influenced tube morphology. In the absence of field evaluation studies, in vitro germination data may provide insight on how specific chemicals may impact pollination processes and further guide in vivo studies, particularly in the case of new chemical formulations.

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E.W. Stover, M. Myers, R.M. Sonoda, and Z. Guo

Stylar-end russetting (SER) is a cosmetic defect of Florida citrus fruit most frequently associated with navel orange. SER is evident as spots or streaks of corky tissue that often form a network of intersecting lines. Occurrence of SER is reported to vary widely from year to year, but some orchards have a history of severe SER, with fruit culled annually for this defect. Growers report that SER is typically first evident in August. The cause of SER has not been determined. Reports of yeast-like fungi inducing russet in pome fruit suggest that similar organisms may be implicated in SER. Yeast-like fungi were isolated on acid PDA from navel oranges in an orchard with frequent severe SER. Strains were selected with a wide range of colony morphology, but were not identified taxonomically. These strains, and strains of Aureobasidium pullulans and Rhodotorula glutinis that caused russetting in pome fruit, were grown in liquid suspension and sprayed on navel orange trees with three repeated applications during July and Aug. 1998. No increase in SER was observed on strain-inoculated trees compared to controls. Two broad-spectrum fungicides were sprayed on other navel orange trees to further explore the possibility that fungi may be involved in SER. GA (gibberellic acid) was also applied in this experiment because it can reduce russetting in apples. All applications were made five times at 3-week intervals in June through Sept 1998. SER was assessed in fruit harvested late Sept. 1998. The proportion of fruit with less than 10% of the surface exhibiting SER was 51% for controls, increased to 69% where myclobutanil was applied at 74 mg a.i./L and increased further to 93% where manganese ethylenebisdithiocarbamate was applied at 1775 mg a.i./L. GA did not significantly influence SER.

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Winfred Cowgill, Kristian Holmstrom, Andrew J. Wyendandt, Jon Clements, and Martha Maletta

Downy mildew (DM) is a serious foliar fungal disease of cucurbits. DM can cause yield losses for New Jersey growers if not properly controlled. In 2004, five chemical control programs were evaluated in a research trial at the Rutgers Snyder Research and Extension Farm (Hunterdon Co.). Materials evaluated were: 1) Phostrol, 5 pt/A; 2) Phostrol, 5 pt/A plus Bravo WS, 3 pt/A; 3) Flint WDG, 2 oz/A alternated with Bravo WS, 3 pt/A plus Nova 40W, 5 oz/A; 4) Maneb 75DF, 2 lb/A plus Champ Formula 2 Flowable, 1 1/3 pt/A; and 5) untreated control. All fungicide programs were applied weekly. Phostrol (Nufarm Americas, Inc.) is a new product with systemic mode of action that is newly labeled for cucurbits for control of DM, but not powdery mildew (PM). The active ingredients are mono- and dibasic-sodium, potassium, and ammonium phosphates. Phostrol and Phostrol plus Bravo were evaluated against industry standard fungicide programs which include alternating chlorothalonil + myclobutanil with strobiluron chemistries on a weekly basis. Fungicide applications were made weekly beginning at first observance of DM in the field on 23 July. Plots were rated for DM and PM incidence and extent of defoliation on 6 Aug. and 24 Sept. Phostrol plus Bravo applied on a weekly basis (7 to 10 days) provided the best control of DM, which appeared much earlier in the season than usual in northern New Jersey. Treatments Phostrol, Flint alternated with Bravo + Nova, Maneb + Champ reduced DM compared to the UTC. Maneb plus Champ provided the best control for PM. At harvest, fruit was graded and weighed. Marketable yield from Phostrol, Phostrol plus Bravo and Maneb plus Champ treatments was significantly higher than the UTC and Flint/Bravo plus Nova treatment. Handle quality was not affected by treatment.

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Cheryl R. Boyer, Janet C. Cole, and Mark E. Payton

–methyl ( LaMondia, 2001a , b ; Ningen, 2003 ), copper hydroxide ( Cole et al., 2005 ; LaMondia, 2001a , b ), azoxystrobin ( Cole et al., 2005 ; LaMondia 2001a ), myclobutanil ( Cole et al., 2005 ), trifloxystrobin ( Cole et al., 2005 ; Schupbach–Ningen et al