Effects of Sprayer Configuration on Efficacy for the Control of Scab on Crabapple Using Electron Beam Analysis

SCANNING VOL. 31,24-27 (2009) Published by Wiley Periodicals, Inc.

l l CHARLES R. KRAUSE l, RICHARD C. DERKSEN l, LEONA E. HORST , HEPING ZHU , RANDALL ZONDAd lUSDA, ARS, Application Technology Research Unit, Wooster, Ohio 20hio State University Extension, Painesville, Ohio

Summary: Foliar diseases like apple scab result in Key words: fungicide, apple scab disease manage significant economic losses to growers each year. ment, cold field emission scanning electron micro Assessment in past studies involved only macro scopy, X-ray microanalysis, spray deposition, scopic disease ratings. More complete knowledge of nursery crops the fate and behavior of fungicide has been needed to reduce pesticide use with less off-target con tamination. Field studies were conducted in a pro duction nursery for over 4 years. A moderately Introduction susceptible cultivar of ornamental crabapple, Malus spp. cv "Candied Apple", was sprayed with a Production of woody environmental and floral fungicide using two sprayer/nozzle configurations. crops represents over 12% of American agricultural The fungicide used in this study was Mankocide, receipts. Unfortunately, fungus diseases like apple combination of CU(OH)2 and mancozeb that per scab caused by Venturia ineaqualis result in millions lllitted electron beam analysis (EBA) identification of dollars of nursery crop losses each year. Effective based on the presence of Cu , MN and Zn in the fungicides must be applied to produce esthetically molecule and formulation. EBA was conducted pleasing plants. New guidelines for registering, using a cold field emission scanning electron using and maintaining pesticides through the U.S. microscopy and energy dispersive x-ray micro Environmental Protection Agency were created by analyzer. Fresh leaf samples were placed on sticky the Food Quality Protection Act of 1996 and stubs after each fungicide treatment. The presence require information on how pesticides are used. or absence of fungal conidia and fungicide residue Research is crucial on fungicide spray methods were measured. EBA permitted direct visualization related to efficacy. Assessment in past studies in and identification of the pathogens, morphologi volved only macroscopic disease ratings (Chatfield cally, and chemical characterization of fungicide et al. 1996). More complete knowledge of the fate present. EBA was useful to quantify disease control and behavior of fungicide will lead to reduced pes related to fungicide coverage, sprayer configuration ticide use with less off-target deposition (Krause and and treatment efficacy. SCANNING 31: 24-27, Derksen 2000; Krause 2000; Krause et al. 2003). 2009. tpublished 2009 by Wiley Periodicals, Inc. The purposes of this study were: devise a technique to directly evaluate and correlate the fungicide coverage with the amount of apple scab disease; to Contract grant sponsors: Horticultural Research Institute; American Nursery and Landscape Association. 'lssess the effects of sprayer/nozzle type on efficacy and disease management in production nurseries. 'This article is a US goverm~ent work and, as such, is in the public domain in the United States of America. Address for reprints: Charles R. Krause, USDA, Agricultural Research Service, Application Technology Research Unit, 1680 Materials and Methods Madison Avenue, Wooster, OH 44691. E-mail: [email protected] Plant Materials Received 30 March 2008; Revised 10 December 2008; Accepted with revision 30 December 2008 Dedicated research plots at a production tree nursery consisting of six crabapple replication DOl IO.1002/sca.20I38 rows with three treatments/replications each were Published online 26 January 2009 in Wiley InterScience (www. interscience.wiley.com) planted. A replication consisted of seven, 2-year-old C. R. Krause et al.: Effects of Sprayer Configuration on Efficacy 25 crabapple whips, Malus spp., using a moderately sus- scopically observed. Free moisture on leaf surfaces ceptible cultivar, 'Candy Apple'. Barrier rows of other was lacking, as recorded by the meteorological sta- landscape tree species were also planted between cra- tion using leaf wetness sensors, indicating that bapple treatment rows to prevent fungicide spray drift. conditions were not conducive for disease development. Subsequent years of the study yielded an in crease in disease as noted macroscopically with Treatments typical symptoms of olive drab lesions and defolia tion (Table I). Treatments were randomized in each of six rows EBA of leaf samples observed during the early as follows: (a) DW, an axial flow, airblast sprayer portion of the year confirmed the lack of the fungal with conventional-high volume nozzle delivering pathogen (conidia) (Fig. lea)). Bar marker indicates 300 psi, traveling at 4 mph; (b) CF, experimental air 10 11m. Flame-shapes conidia (CON) verified the curtain sprayer or cross-flow fan sprayer with air presence of the pathogen on the leaf surfaces Malus induction nozzles delivering 120 psi at 4 mph; (c) spp. cultivar. EDXA confirmed the absence of Cu, unsprayed control. Electron beam analysis (EBA): Mg and Zn, the constituents of the fungicide spray a combination of scanning electron microscope and residue (Fig. l(b)). Even when limited disease energy dispersive x-ray analysis (EDXA). A cold occurred on the crabapples in the spring of the first field emission scanning electron microscope, Model 2 years, EBA confirmed the presence of the patho 4700, Hitachi High Technologies America, Plea gen despite the lack of visible symptoms. The lack santon, CA equipped with EDXA, Model Voyager free moisture did not produce significant fungal in II, (Thermo-Noran, Madison, WI) with a high-angle fection. While fungicide coverage on sprayed leaves detector was used. EBA equipment was located at was observed with EBA, low disease pressure did the Molecular and Cellular Imaging Center in not permit quantification of differences in efficacy in the Ohio Agricultural Research and Development subsequent years. Center, Wooster. Operational conditions were: 10 kV EBA confirmed the presence of the pathogen acceleration voltage at 12 rom working distance. (CON) and fungicide residue (arrows) was noted as Bioassay and leaf analysis. Leaves were collected in Figures 2(a) and 3(a) on leaves sprayed with CF from each treatment following each spray, mounted and DW. Bar markers indicate 111m. EDXA con on ~tubs with conductive sticky tabs (Ted Pella, firmed the presence of Cu, Mg and Zn on leaves Tustin, CA) for bioassay and EBA. EBA permitted sprayed with fungicide as shown in Figures 2(b) direct visualization of 3 fields per sample, and and 3(b). morphological identification of the pathogens, and chemical characterization of any fungicide present. The fungicide used in this study was Mankocide, a Conidial Presence on Leaf Tissue (Percent of Leaves combination of the fungicides, Cu(OH)2 and Infected) mancozeb, that permitted EBA identification based on the presence of Cu, MN and Zn in the Application of fungicide had mixed results. The molecule. Disease incidence and fungicide deposi CF (cross-flow sprayer) appeared to yield decreased tion were noted and recorded during spray percentage of conidia found on leaf samples whereas treatments. the DW had no effect as the season lengthened (Fig. 3).

Weather Stations TABLE I Analysis of fungal conidia on leaf samples collected A portable meteorological station (Campbell at a nursery field site Scientific Instruments) was installed within the ex Fungal Conidia perimental plot to remotely monitor air tempera Sprayer Meanl ture, leaf wetness, relative11Umidity, wind speed and direction, rainfall and solar radiation, according to Control(4) 46.86a guidelines of the United States National Oceanic CF(1) 11.36b DW normal(2) 30.71ab and Atmospheric Administration (NOAA). LSD = 21.65

Analysis ofnumbers ofconidia on plants treated with various Results and Discussion sprayers as were detected with CFE-SEM. Numbers of fungal conidia on leaves ofplants treated with the cross-flow fan (CF) sprayer were significantly less than plants treated During the three of the four growing seasons, with either air blast (DW) sprayer. little apple scab disease symptoms were macro- lNumbers with the same letters do not differ significantly. 26 SCANNING VOL. 31, 1 (2009)

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Fig 1. Electron beam analysis of leaf samples. (a) Surface of unsprayed leaf confirmed the presence of numerous fungal conidia (CON) of the pathogen. Bar = 100 am. (b) EDXA of unsprayed control showing a lack of the elements, Cu, S that would be present in fungicide residue.

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keV Fig 2. (a) Surface ofleaf sprayed with fungicide confirmed the presence ofthe fungal conidia. Note fungicide residue with arrows. Bar = 100 am. (b) EDXA of sprayed control showing the presence of the fungicide and the elements, Cu, S that are present in fungicide residue.

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Fig 3. (a) Surface of a leaf sprayed with fungicide confirmed the presence of fungal conidia (CON). Note fungicide residue. Bar = 50 am. (b) EDXA leaf surface sprayed with fungicide showing the elements, Cu, S that showed the presence ofthe fungicide residue.

The percent of leaves infected with fungal conidia percentage of infected leaves (Fig. 4). In other observed with EBA on the control treatment con words, the percent of leaves infected with fungal tinued to climb after a leaf wetness period in May. conidia as detected with EBA on crabapple cv The percentage of leaves infected with conidia "Candy Apple" leaf samples, the cross-flow fan fluctuated with the CF sprayer revealing the lowest sprayer (CF) treatment appeared to reduce the C. R. Krause et al.: Effects of Sprayer Configuration on Efficacy 27

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Fig 4. The percent of leaves infected with fungal conidia as detected with EBA on crabapple "Candy Apple" leaf samples, the cross-flow fan sprayer (CF) treatment appeared to reduce the amount ofconidia found on leaf samples while the airblast sprayers (DW) had no effect as the season lengthened compared with unsprayed controls. amount of conidia found on leaf samples whereas long-term project. The authors also thank Mr Rolly the airblast sprayers (DW) had no effect as the Hart for applying spray and Jay Daley, Sunleaf season lengthened compared with unsprayed con Nursery, for their cooperation during this in trols. Statistical analysis of the samples showed the vestigation. cross-flow samples had significantly less fungal Disclaimer: Names are necessary to report fac conidia present than the control, but not sig tually on available data, however, the U.S. De nificantly different from the other treatments as partment of Agriculture, Agricultural Research shown in Table I. Service and the Ohio State University, neither This is a technique paper to be used in the de guarantee nor warrant the standard of a product. velopment of experimental methods essential for Further, the use of the name by USDA or OSU studIes of apple scab disease. The use of fungicides implies no approval of the product to the exclusion as tracers for EBA was developed as part of the of others that may be suitable. This article is in analytical protocol for studying spray efficacy. the public domain and not copyrightable. It may be Specimen handling technology was also developed freely reprinted with customary crediting of the for subsequent studies. Techniques developed in this source. study will be adapted for assessment of other disease management methods. EBA was useful to micro scopically quantify and observe disease control related to fungicide coverage, sprayer configuration and treatment efficacy. Improved knowledge of the References basis of efficacy and coverage will improve grower Chatfield JA, Draper EA, Cochran KD: Comprehensive profitability; protect farm workers, enhance con aesthetic evaluations of crabapples in Ohio: 1993-1995. sumer confidence in crop safety and reduce the im Malus: Int Ornamental Crabapple Bull 0(1), 5-16 (1996). pact of fungicides on the environment. Krause CR: Partnerships with the Green Industry: the new Molecular and Cellular Imaging Center. Special Circular 177. Ohio Agricultural Research and Development Center, The Ohio State University, 113-117 (2000). Acknowledgements Krause CR, Derksen RC: Comparison of electrostatic and 'Coldfog sprayers with cold field emission scanning elec This research is spoll£ored in part through a tron microscopy and energy dispersive x-ray micro analysis. Proc BCPA 3, 1099-1104 (2000). grant from the Horticultural Research Institute, Krause CR, Derksen RC, Horst L, Zondag R, Brazee RD, American Nursery and Landscape Association, Klein MG, Reding ME: The effects of sprayer config Washington, DC. The USDA, ARS, Application uration on efficacy for the control of scab on crabapple. Technology Unit also expresses its appreciation to Ornamental Plants: Annual Reports and Research Reviews, 2002. The Ohio State University, Ohio Agri Mr Robert Lyons, President, Sunleaf Nursery, cultural Research and Development Center, Special Madison, OH for the use of the nursery during this Circular 193, 65-68 (2003).