JOBNAME: hortte 18#4 2008 PAGE: 1 OUTPUT: August 29 00:35:23 2008 tsp/hortte/169193/01140 Some contain pyraclostrobin as the Seasonal Applications of a Pyraclostrobin and sole fungicidal material (e.g., Cabrio Boscalid Mixture Do Not Impact Same-year EG; BASF Corp., Research Triangle Park, NC) and some are marketed Peach Fruit Quality Attributes as a premixture of pyraclostrobin + boscalid (Pristine, BASF). The pyr- 1,3 2 aclostrobin + boscalid mixture is G. Schnabel and C.H. Crisosto currently the only formulation con- taining pyraclostrobin registered for ADDITIONAL INDEX WORDS. Prunus persica, scab, Pristine, greening effect, fungicide, disease control in stone fruit in the firmness United States. Most yield and quality studies SUMMARY. Quinone outside inhibitor (QoI) fungicides can improve the yield and with QoI fungicides have focused on quality of cereal crops in the absence of disease pressure through the so called wheat or barley (Hordeum vulgare). ‘‘greening effect,’’ but little is known about the potential beneficial effects on deciduous tree fruit crops. In a multiyear and multicultivar study carried out in However, more studies are emerg- South Carolina (2005 and 2006) and California (2006), we examined the potential ing that document disease control influence of the QoI fungicide pyraclostrobin on antioxidant activity and and additional benefits in other crops, commercially important peach (Prunus persica) fruit quality attributes, including such as rice (Oryza sativa), potato fruit size, coloration, firmness, soluble solids concentration, and yield. (Solanum tuberosum), and tomato Experimental orchards were sprayed according to commercial guidelines to (Solanum lycopersicum) (Harrison and manage insect pests and diseases. A pyraclostrobin + boscalid mixture was applied Tedford, 1999; Siviero and Azzaro, up to five times per season starting 1 week after the physiological stage of ‘‘shuck 2001; Stevenson et al., 1999). Re- off’’ until 1 to 2 weeks before harvest. Fruit size was measured weekly between ports on fruit are rare and it is not ‘‘shuck off’’ and harvest, whereas the other fruit quality attributes were clear if the observed increase in total determined at harvest. Results indicate no consistent impact of the pyraclostrobin + boscalid mixture on same-year fruit size development or other yield or percentage of marketable fruit quality attributes in orchards with no or very little disease pressure. To our fruit was a result of improved disease knowledge, this is the first in-depth evaluation of the potential effects of a control or the ‘‘greening effect’’ QoI fungicide on commercially important tree fruit quality attributes. (Ammermann et al., 2000; Heaney and Knight, 1994). The goal of this study was to investigate possible pplications of the quinone and Bryson, 1998; Jørgensen and same-year beneficial effects of the outside inhibitor (QoI) fungi- Nielsen, 1994, 1996; Nielsen and QoI fungicide pyraclostrobin in the Acides azoxystrobin, kresoxim- Jørgensen, 1995). These yield in- absence of disease pressure on anti- methyl, trifloxystrobin, picoxystrobin, creases in the absence of disease pres- oxidant activity and commercially or pyraclostrobin can increase yield sure are believed to be a result of a important peach fruit quality attrib- and quality of cereal crops, likely delay in leaf senescence, which is also utes, including fruit size, coloration, due to improved disease control known as the ‘‘greening effect’’ of QoI firmness, soluble solids concentra- (Ammermann et al., 2000; Godwin fungicides. tion, and yield. et al., 2000; Jones and Bryson, 1998; QoI fungicides, such as pyraclos- Margot et al., 1998; Noon, 1997). trobin, are grouped and listed under Materials and methods However, in some crops, a yield Fungicide Resistance Action Commit- ORCHARD PREPARATION AND increase was observed in the absence tee (FRAC) code 11 due to their iden- EXPERIMENTAL SETUP. Experimental of disease symptoms. For example, an tical modes of action. They bind to the peach orchards in South Carolina increase in yield in winter wheat (Tri- ubihydroquinone reduction site, the and California were used in this study, ticum aestivum) showing no apparent Qo-site of complex bc1, thus inhibiting and pests and diseases were managed disease symptoms was observed when electron transfer between cytochrome according to grower standards. The azoxystrobin was applied (Jones b and cytochrome c1 in the respiratory South Carolina orchards were estab- chain (Becker et al., 1981; Von Jagow lished in 1995 at the Clemson Uni- Technical Contribution No. 5324 of the Clemson University Experiment Station. This material is based and Link, 1986). Pyraclostrobin is versity Musser Fruit Research Farm upon work supported by the CSREES/USDA under available in various formulations. at Seneca. Orchards with the early project number SC-1000642. We thank Karen Bryson, Sam Hudson, Billy Newall, David Garner, and Vanessa Bremer for technical assistance, Kerik Cox (Cornell University) and Wil- Units liam Bridges (Clemson University) for helping with the statistical analysis, and BASF Corporation for To convert U.S. to SI, To convert SI to U.S., financial support of this study. multiply by U.S. unit SI unit multiply by 1Department of Entomology, Soils, and Plant Scien- 0.3048 ft m 3.2808 ces, Clemson University, 120 Long Hall, Clemson, 3.7854 gal L 0.2642 SC 29634 9.3540 gal/acre LÁha–1 0.1069 2Department of Plant Sciences, University of Califor- 25.4 inch(es) mm 0.0394 nia, Davis, Davis, California. Located at Kearney 0.4536 lb kg 2.2046 Agricultural Center, 9240 South Riverbend Ave., 70.0532 oz/acre gÁha–1 0.0143 Parlier, CA 93648 1 ppm mgÁg–1 1 3Corresponding author. E-mail: schnabe@clemson. 6.8948 psi kPa 0.1450 edu. (°F – 32) O 1.8 °F °C(1.8·C) + 32 678 • October–December 2008 18(4) JOBNAME: hortte 18#4 2008 PAGE: 2 OUTPUT: August 29 00:35:24 2008 tsp/hortte/169193/01140 Protection, Greensboro, NC) and phosmet (Imidan 70WSB; Gowan, Yuma, AZ) on 8 Apr.; captan (Captec 4L; Micro Flo, Memphis, TN) on 14 Apr.; captan and phosmet on 25 Apr., 6 May, 18 May, and 4 June; micron- ized sulfur (Microthiol Disperss 80DF; Ceraxagri, Philadelphia) and phosmet on 16 June; captan and phosmet on 30 June (‘Contender’ only), and pro- piconazole (Orbit 3.6EC; Syngenta Crop Protection) on 1 July (‘Coro- net’ only). In 2006, the ‘‘untreated’’ program consisted of the following fungicide and insecticide applications: captan and phosmet on 3 Apr.; chlor- othalonil (Bravo Weather Stik 6F; Syngenta Crop Protection) and phos- met on 10 Apr.; micronized sulfur and phosmet on 20 Apr.; captan and phosmet on 3 May; micronized sulfur and phosmet on 25 May, 8 May, and 22 June; fenbuconazole (Indar 75WSP; Rohm and Haas, Philadel- phia) on 22 and 29 June; and captan on 6 July (‘Contender’ only). All fun- gicides and insecticides were applied with an air-blast sprayer at label rates using 200 gal/acre water. The sec- ond fungicide program consisted of the ‘‘untreated’’ program plus appli- cations of a pyraclostrobin + boscalid mixture (Pristine) applied at 14.5 oz/ acre formulated product. In 2005, Fig. 1. Influence of seasonal pyraclostrobin + boscalid applications on mean fruit peaches were sprayed with a pyraclos- size of ‘Coronet’ peaches in experimental years (A) 2005 and (B) 2006. trobin + boscalid mixture on 15 Apr., Pyraclostrobin + boscalid mixture was applied four (2005) and five (2006) times in 2-week intervals between the phenological stage of ‘‘shuck split’’ and 1 to 2 weeks 29 Apr., 31 May (‘Coronet’ only), 16 before harvest. Letters above mean values indicate significances between treatments June, 1 July (‘Contender’ only), and at P < 0.05; NS = nonsignificant (1 mm = 0.0394 inch). 12 July (‘Contender’ only). In 2006, ‘Coronet’ and ‘Contender’ peaches were sprayed with pyraclostrobin + ripening cultivar Coronet and the ‘‘untreated’’ control treatment) were boscalid on 25 Apr., 9 May, 23 midseason cultivar Contender were kept pest and disease free following May, 6 June, and 20 June. Trees were used for this study. ‘Contender’ California pest and disease management sprayed to runoff (1.5 gal/tree) at 200 peaches ripen 3 weeks later than guidelines (Adaskaveg et al., 2004). psi pressure using a handgun sprayer. the ‘Coronet’ peaches. All trees were In each of the two cultivars from In California, the pyraclostrobin + planted on ‘Guardian’Ò rootstock, South Carolina, spray programs boscalid mixture was applied at differ- and spacing between trees and rows were replicated 10 times in a random- ent physiological stages using 12 ‘May was 6 m. Insecticides, fungicides, and ized complete block design with Glo’ or 18 ‘O’Henry’ single-tree rep- herbicides were applied to all trees single-tree replications. Trees were lications in a randomized complete according to recommendations of the re-randomized each year. The first block design. ‘O’Henry’ received the Southeastern Peach Spray Guide program (untreated) did not contain following five treatments: 1) one (Brannen et al., 2005). Thinning any pyraclostrobin or other QoI fun- spray during bloom only (S-1); 2) was conducted by hand twice within gicide applications and consisted of two sprays during pit hardening only 2 weeks after the phenological stage routine commercial applications of (S-2); 3) two preharvest sprays only, of ‘‘shuck split’’ to ensure even thin- fungicides and insecticides necessary 14 and 7 d before predicted harvest ning among trees. The California or- for production of commercially (S-3); 4) one spray at bloom plus two chards were located at the University acceptable fruit. In 2005, this pro- sprays during pit hardening plus two of California, Kearney Agricultural gram contained the following fungi- preharvest sprays 14 and 7 d before Center at Parlier. The nectarine culti- cide and insecticide applications: predicted harvest (S-1-2-3); and 5) an var May Glo and the peach cultivar chlorothalonil (Equus 720; Griffin, untreated control. ‘May Glo’ received O’Henry were used for this study.