Progress 10/01/03 to 09/30/08
Outputs
The objectives of the first study were to examine the effect of several rates of 1-MCP from 10 to 100 nL per L on stem end decay caused by Botrytis cinerea and to evaluate the effects of prestorage treatment with 1-MCP, hexanal, and 1-MCP + hexanal on decay of d'Anjou pear (Pyrus communis L.) fruit in long-term cold storage. In the second study, we identified a new disease of sweet cherry. During May to June 2006, Lapins sweet cherry (Prunus avium) trees were observed with white mold on blossoms and young fruit in two commercial orchards in central Oregon (Wasco County).
Impacts
In the first study, a combination of 1-MCP and hexanal at optimized rates may reduce storage decay, control superficial scald, and allow normal ripening of d'Anjou pear fruit. 1-MCP at 300 nL per L reduced bull's-eye rot and Phacidiopycnis rot. Stem end gray mold also was reduced by 1-MCP at 300 nL per L, and reduction at rates from 10 to 100 nL per L was significant in one of two trials. Snow-mold rot was reduced by 1-MCP at 30 nL per L. Hexanal alone reduced snow mold but increased blue mold caused by Penicillium expansum. The combination of 1-MCP and hexanal affected decay similar to 1-MCP. However, hexanal in combination with 1-MCP negated the effect of 30 nL per L 1-MCP on firmness but did not counteract the effect of 300 nL per L 1-MCP. Additional research is needed on the mode of action of the 1-MCP/hexanal combination and use of this combination on pear fruit in commercial storage and ripening regimes. In the second study, S. sclerotiorum has been reported to
cause green fruit rot of stone fruits, including almond, apricot, nectarine, and peach. Thirty percent of fruit clusters and entire blossoms clusters were affected. Rot on fruit was firm, light brown and covered the entire fruit, extending halfway up the pedicel. Affected blossoms were light brown, sticking to adjacent fruit and blossoms. A white fungus producing sclerotia measuring 4-8mm in diameter was recovered from all isolations. Koch's postulates were satisfied by inoculating green, pea-sized Lapins cherry fruit with mycelial plugs colonized by the white fungus. Infections and symptoms like those seen in the orchard were produced. The same sclerotia-producing fungus was recovered from all inoculated fruit. Based on sclerotia size and nested polymerase chain reaction (PCR), using fungal-universal primers ITS4/ITS5 and SSFWD/SSREV, the pathogen was identified as Sclerotinia sclerotiorum (Lib.) de Bary. S. sclerotiorum is endemic on wheat in Wasco County. The affected orchards are
surrounded by wheat fields where infection was particularly serious in spring 2006 compared to previous years. Rot on cherries was first observed and very severe in May 2005, with infection mainly on leaves of all trees across 45 hectares. New cherry infections continued to appear until mid-June. During 2006, most infection was on fruit with some leaf spotting. Both years had unusually wet springs with 12.2cm rainfall received during spring 2005 and 12.4cm during spring 2006, well above the 6.81cm average for the previous 5 years. This is the first disease report of S. sclerotiorum causing blossom blight and green fruit rot on sweet cherry in Oregon. During unusually wet seasons, additional control measures may be needed to manage this new disease.
Publications
- Spatafora, J.W., Sung, G., Johnson, D., Hesse, C., O Rourke, B., Serdani, M., Spotts, R., Lutzoni, F., Hofstetter, V., Miadlikowska, J., Reeb, V., Gueidan, C., Fraker, E., Lumbsch, T., Lucking, R., Schmitt, I., Hosaka, K., Aptroot, A., Roux, C., Miller, A.N., Geiser, D.M., Hafellner, J., Hestmark, G., Arnold, A.E., Budel, B., Rauhut, A., Hewitt, D., Untereiner, W.A., Cole, M.S., Scheidegger, C., Schultz, M., Sipman, H., and Schoch, C.L. 2006. A five-gene phylogeny of the Pezizomycotina. Mycologia 98:1018-1028.
- Spotts, R.A., Sholberg, P.L., Randall, P., Serdani, M., and Chen, P.M. 2007. Effects of 1-MCP and hexanal on decay of d'Anjou pear fruit in long term cold storage. Postharvest Biol. Technol. 44:101-106
- Serdani, M., and Spotts, R.A. 2007. First report of blossom blight and green fruit rot of sweet cherry caused by Sclerotinia sclerotiorum (Lib.) de Bary in Oregon. Plant Disease 91:1058.
- Bai, J., Plotto, A. and Spotts, R. 2007. Humidity maintenance clamshell and ethanol vapor improve quality of intact and fresh-cut cherries. International Fresh Cut Produce Association Annual Conference (Abstract), Reno, NV, April 22-24.
- Spotts, R.A., and Serdani, M. 2007. A preharvest model to predict gray mold of pear fruit in long term cold storage. Plant Dis. 97 (suppl.):S110.
- Spotts, R. A. 2007. New Projects, New Discoveries in Plant Pathology. MCAREC Newsletter 8:1,5.
- Bai, J., Barckley, K., Spotts, R., Serdani, M., and Laraway, D. 2007. Effect of field sprays of 1-MCP on quality and storability of Anjou pears. HortSci. 42:981.
- Castagnoli, S., H. Riedl, R. Spotts, L. Long, A. Walston, J. Pscheidt, and J. Olsen. Pest Management guide for tree fruits in the Mid-Columbia area. 2007. EM8203-E. 89 pp.
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Progress 01/01/06 to 12/31/06
Outputs
A hot water pressure process (HWP) was evaluated for its effect on conidia of P. expansum and on development of blue mold, gray mold, and mucor rot of d'Anjou pear fruit. Spores were removed from the water system through dilution and also as a result of hot water in the system that was lethal to the spores. When the system was heated, viable spores were not detected after 2-4 hours of operation. Reductions in decay in the HWP system were 36, 29, and 13% for B. cinerea, M. piriformis, and P. expansum, respectively. The response of P. expansum appeared related to the length of time fruit was in cold storage. Heat injury was observed on fruit treated with 40 and 50C water but not on fruit at 30C nozzle temperature. The HWP system described in this study should be considered as a component of an integrated decay control strategy. Cankers formed on pear branches after inoculations with mycelia of Neofabraea alba and N. perennans, causal agents of bull's eye rot of pear
fruit. The highest proportions of successful inoculations followed fall and winter inoculations. Cankers induced by N. perennans were larger than those induced by N. alba. Small, superficial cankers were obtained after inoculations with conidia of N. perennans on wounded branches of pear trees. Sporulation of both pathogens on mycelial-induced cankers occurred throughout the year with the largest amount of conidia produced at the end of summer and during fall. Sporulation on cankers induced by N. perennans spanned at least two years. Copper sulfate reduced sporulation on cankers induced by N. alba, while copper sulfate, trifloxystrobin and ziram applied to sporulating cankers reduced germination of conidia of N. perennans. Botrytis cinerea was capable of colonizing and persisting in tissue pieces of six common weed species found in pear orchards in Oregon from mid-summer until pear harvest in early September. Sporulation occurred on blackberry mummies in orchard perimeters and ranged
from 5,700 to 55,000 conidia per mummy at pear harvest. Conidia of B. cinerea also were observed on fresh blackberry fruit in 2 of 3 years. Sclerotia were present on only a few of the naturally infected pear fruit on the orchard floor through November, but sclerotia production increased greatly between mid-November and mid-December. Over 90% of sclerotia from naturally infected, overwintered fruit germinated in the laboratory when collected 6 to 8 months after infection. Sclerotia formed on pear fruit inoculated with 28 different paired combinations of 22 isolates in the laboratory. Viability of sclerotia in inoculated pear fruit that overwintered on the orchard floor was 44 to 59% in March and April, and then declined steadily to about 25% at pear harvest. Germination of sclerotia was both sporogenic and myceliogenic. No apothecia were observed in the field or laboratory. An integrated approach to control is needed to deal with these multiple sources of potential inoculum.
Impacts
The hot water pressure process described in this study should be considered as a component of an integrated decay control strategy. The system reduced gray mold and mucor rot as well as blue mold in recently-harvested pears. The system cannot be relied on to give adequate decay control alone, and integrated measures are necessary for satisfactory levels of commercial decay control. Pear wood is susceptible to infection by N. perennans and N. alba, even though cankers caused by N. perennans may not occur naturally. Conidia of N. alba and N. perennans were produced on artificially-induced cankers almost constantly, increasing at the end of the growing season and during harvest time, when fruit susceptibility is highest. Fungicides commonly applied in pear orchards had little effect on sporulation of the pathogens, but can affect conidial germination, which should in turn influence disease incidence. An integrated approach is needed to deal with the multiple sources of
potential inoculum of Botrytis cinerea in the orchard to control gray mold in cold storage. This approach may include removal of fallen fruit from the orchard immediately after harvest, reduction in weed growth in orchard row middles by using irrigation emitters that water only the trees or by using synthetic ground covers, and eliminating blackberry plants on orchard perimeters. Further study is needed to determine if this integrated approach will result in reduced fungicide usage.
Publications
- Neven, L.G., Hansen, J.D., Spotts, R.A., Serdani, M., Mielke, E.A., Bai, J., Chen, P.M., and Sanderson, P.G. 2006. Effect of high-pressure hot water washing treatment on fruit quality, insects, and disease in apples and pears: Part IV: Use of silicone-based materials and mechanical methods to eliminate surface arthropod eggs. Postharvest Biol. and Technol. 40: 230-235.
- Spotts, R.A., and Serdani, M. 2006. Inoculum sources of Botrytis cinerea important to pear orchards in the Pacific Northwest. Plant Dis. 90:750-754.
- Henriquez, J.L., Sugar, D., and Spotts, R.A. 2006. Induction of cankers on pear tree branches by Neofabraea alba and N. perennans, and fungicide effects on conidial production on cankers. Plant Dis. 90:481-486.
- Serdani, M., Spotts, R.A., Calabro, J.M., Postman, J.D., and Qu, A. 2006. Evaluation of the USDA National clonal Pyrus germplasm collection for resistance to Podosphaera leuchotricha. HortScience 41:717-720.
- Bai, J., Mielke, E.A., Chen, P.M., Spotts, R.A., Serdani, M., Hansen, J.D., and Neven, L.G. 2006. Effect of high-pressure hot-water washing treatment on fruit quality, insects, and disease in apples and pears. Part I. System description and the effect on fruit quality of Anjou pears. Postharvest Biol. Technol. 40:207-215.
- Spotts, R.A., Serdani, M., Mielke, E.A., Bai, J., Chen, P.M., Hansen, J.D., Neven, L.G., and Sanderson, P.G. 2006. Effect of high-pressure hot water washing treatment on fruit quality, insects, and disease in apples and pears. Part II. Effect on postharvest decay of Anjou pear fruit. Postharvest Biol. Technol. 40:216-220.
- Hansen, J.D., Heidt, M.L., Neven, L.G., Mielke, E.A., Bai, J., Chen, P.M., and Spotts, R.A. 2006. Effect of high-pressure hot-water washing treatment on fruit quality, insects, and disease in apples and pears: Part III. Use of silicone-based materials and mechanical methods to eliminate surface pests. Postharvest Biol. Technol.:40: 221-229.
- T.Y. James, F.Kauff, C.L. Schoch, P.B. Matheny, V. Hofstetter, C.J. Cox, G. Celio, C. Guiedan, E. Fraker, J. Miadlikowska, T. Lumbsch, A. Rauhut, V. Reeb, A. E. Arnold, A. Amtoft, J.E. Stajich, K. Hosaka, G.-H. Sung, D. Johnson, B. ORourke, M. Binder, J.M. Curtis, J.C. Slot, Z. Wang, A.W. Wilson, A. Schusler, J.E. Longcore, K. ODonnell, S. Mozley-Standridge, D. Porter, P. M. Letcher, M. J. Powell, J.W. Taylor, M.M. White, G.W. Griffith, D.R. Davies, J. Sugiyama, A.Y. Rossman, J.D. Rogers, D.H. Pfister, D. Hewitt, K. Hansen, S. Hambleton, R.A. Shoemaker, J. Kohlmeyer, B. Volkmann-Kohlmeyer, R.A. Spotts, M. Serdani, P.W. Crous, K.W. Hughes, K. Matsuura, E. Langer, G. Langer, W.A. Untereiner, R. Lucking, B. Budel, D.M. Geiser, A. Aptroot, W.R. Buck, M.S. Cole, P. Diederich, D.M. Hillis, C. Printzen, I. Schmitt, M. Schultz, R. Yahr, A. Zavarzin, D.S. Hibbett, F. Lutzoni, D.J. McLaughlin, J.W. Spatafora, R. Vilgalys. 2006. Reconstructing the early evolution of fungi using
a six gene phylogeny. Nature 44
- Serdani, M., and Spotts, R.A. 2006. Real-time PCR for quantification of decay spore populations in packinghouse water. Abstr. Phytopathology 96(suppl.):S171.
- Grove, G., Falacy, J., Spotts, R., Glawe, D., Mahaffee, W., Galloway, H., and Lunden, J., 2006. Detection of Podosphaera clandestina and Erysiphe necator in the air of cherry (Prunus avium L.) orchards and grape (Vitis vinifera L.) vineyards using PCR and species-specific primers. Abstr. Phytopathology 96(suppl.):S168.
- Calabro, J.M., Spotts, R.A., and Grove, G.G. 2006. Preliminary studies on sweet cherry powdery mildew resistance to DMIs in the Pacific Northwest. Abstr. Phytopathology 96(suppl.):S18.
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Progress 01/01/05 to 12/31/05
Outputs
A core subset of 31 Asian (ASN) cultivars, 119 European (EUR) cultivars, 8 hybrid cultivars, and 45 species selections of the genus Pyrus was evaluated for resistance to pear scab caused by Venturia pirina and powdery mildew (PM) caused by Podosphaera leucotricha. Three potted, grafted trees of each core accession were artificially inoculated and grown under greenhouse conditions ideal for infection. Orchard trees were evaluated during 10 years for natural fruit scab (FS), and during 3 years for percent of leaves with leaf scab (LS). Potted trees were evaluated for PM symptoms from natural field infections during one season. FS was rated on a scale of 1 to 9 (1 = no scab). Only 34 clones produced leaf symptoms following greenhouse inoculation, however 24 of these also rated high for natural LS in the field. All ASN were nearly free of both FS and LS. No ASN had a mean FS rating greater than 4, and 42% had no scab or negligible ratings. Thirty eight percent of EUR had
mean FS ratings >4, and 8% had no scab or negligible scab. Average LS incidence was 3.4% of leaves for EUR compared to 0.4% for ASN. More than 64% of EUR had >1% LS. EUR with negligible FS and LS include Arganche, Batjarka, Brandy, Erabasma, Muscat, and Passe Crassane. Incidence of both FS and LS in hybrid cultivars was intermediate between that of ASN and EUR. Most species selections had negligible FS, except P. cordata which rated 5. Of 23 EUR rated high for FS, 21 also had >1% LS. For powdery mildew, EUR were overall more susceptible than ASN, with 47% of EUR and 25% of ASN (field) and 93% of EUR and 43% of ASN (greenhouse) being infected with PM. Average PM incidence in the greenhouse (8% for ASN and 31% for EUR) was much higher compared to field infections (2% for ASN and 6% for EUR). In the field, 33% ASN and 38% of EUR with PM symptoms had a mean PM value of >10%. Symptoms were more severe in the greenhouse, with 62% ASN and 80% of EUR with PM symptoms having a mean PM value of
>10%. This study has identified pear cultivars that may be grown without chemical scab and PM control, and that may be useful as parents in breeding for resistance. A three-part model was developed to predict pear scab risk. The model has been applied successfully since 2001, but improvements continue to be made. Using all three parts of the model, control of pear scab at MCAREC was excellent in 2001-2005 with 1 to 2 fungicide sprays per year. We had almost no scab in our autumn evaluations and omitted the first spray of the season each year. This represents a 50 to 67% reduction in fungicide usage.
Impacts
This study has identified pear cultivars that may be grown without chemical pear scab and powdery mildew control, and that may be useful as parents in breeding for resistance. Also, weather station networks are being augmented, pear scab model validation research conducted, and new GIS and web delivery technologies developed for successful implementation of the scab model. This will benefit pear growers throughout the Pacific Northwest with timely, accurate risk prediction for pear scab, resulting in maximum control at minimum cost. Fungicide usage has been reduced by over 50% thus far.
Publications
- Postman, J.D., Spotts, R.A. and Calabro, J. 2005.Scab resistance in Pyrus germplasm. Acta Hort. (ISHS) 671:601-608 http://www.actahort.org/books/671/671_84.htm.
- Serdani, M., Spotts, R.A., Calabro, J.M. and Postman, J.D. 2005.Powdery mildew resistance in Pyrus germplasm. Acta Hort. (ISHS) 671:609-613 http://www.actahort.org/books/671/671_85.htm.
- Gariepy, T.D., Rahe, J.E., Levesque, C.A., Spotts, R.A., Sugar, D, and Henriquez, J.L. 2005. Neofabraea species associated with bulls eye rot and cankers of apple and pear in the Pacific Northwest. Can. J. Plant Pathology 27:118-124.
- Spotts, R.A., Serdani, M., and Coop, L.B. 2005. Where has all the pear scab gone? Proceed. Oregon Horticultural Soc. Paper available at http://www.oregonhorticulturalsociety.org/newsletter/index.php.
- Calabro, J., and Spotts, R.A. 2005. Development of real-time polymerase chain reaction for the detection and quantification of Podosphaera clandestina on sweet cherry. Phytopathology 95:S16.
- Grove, G., Spotts, R., Mahaffee, W., Galloway, H., and Lunden, J., 2005. Detection of Podosphaera clandestina in the air of cherry (Prunus avium L.) orchards using PCR and species-specific primers. Phytopathology 95:S37.
- Olaya, G., Heidel, T., Spotts, R., Sanderson, P., Rosenberger, D., and Tally, A. 2005. Sensitivity of Penicillium expansum isolates to the phenypyrrole fungicide fludioxonil. Phytopathology 95:S77.
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Progress 01/01/04 to 12/31/04
Outputs
The objectives of this study were to determine the timing of Botrytis cinerea infection of pear stems and calyxes in the orchard during the growing season and to investigate the development of gray mold decay in storage. Stem tissue was generally resistant to infection by B. cinerea until July, after which time the fungus was isolated from the abscission zone of the stem. Levels of infection were higher in stems sampled at harvest than at previous sample times, and the pathogen was regularly isolated from stems at harvest. Little or no stem end gray mold was detected in d'Anjou pears after three months in storage. The incidence of stem end gray mold increased between three and six months in storage, and further increases occurred between six and eight months. Inoculated calyxes were more susceptible to infection soon after full bloom (April to May) than later in the season. However, inoculation of calyxes in April or May did not result in higher levels of calyx end
gray mold in storage. Thus, the use of preharvest levels of calyx infection is precluded as a predictor of calyx end gray mold in storage. In addition, application of benomyl in the orchard reduced the level of B. cinerea in blossoms but had no effect on levels of gray mold of fruit in storage. Packing and shipping fruit within 3 to 6 months of harvest may mitigate economic losses due to gray mold. The objectives of a second study were to determine the relative incidence of decay in air-stored Anjou pear fruit and to investigate the effect of a prestorage thiabendazole drench on incidence of decay in commercial controlled atmosphere-stored Anjou pears. Neofabraea spp. caused the greatest level of decay in air-stored fruit, followed by Botrytis cinerea and then Penicillium expansum. Decay caused by stem end infections of B. cinerea was higher than calyx end or puncture infections by this pathogen. Secondary infections by B. cinerea caused high levels of decay. Botrytis cinerea
infections of punctures (1.27%), stems (1.09%) and calyxes (0.45%) were responsible for the greatest level of decay in commercial controlled atmosphere storage of undrenched fruit. Low incidence of decay caused by P. expansum (0.12%) occurred in undrenched fruit. A thiabendazole drench prior to storage significantly reduced decay caused by gray mold, as well as that caused by Neofabraea spp. Decay caused by P. expansum was significantly higher in drenched than in undrenched fruit. These results support the current recommendations of a single postharvest application of thiabendazole to control postharvest decay in Anjou pear fruit.
Impacts
Gray mold decay developed most rapidly after 6 months of cold storage. Thus, packing and shipping pear fruit within 3 to 6 months of harvest should mitigate economic losses due to gray mold. A thiabendazole drench prior to storage reduced gray mold and bull's-eye rot but increased blue mold. A single postharvest application of thiabendazole is recommended to reduce overall decay and avoid development of resistance to the fungicide.
Publications
- Lennox, C.L., and Spotts, R.A. 2004. Timing of preharvest infection of pear fruit by Botrytis cinerea and the relationship to postharvest decay. Plant Dis. 88:468-473.
- Lennox, C.L., Spotts, R.A., and Booyse, M. 2004. Incidence of postharvest decay of Anjou pear and control with a thiabendazole drench. Plant Dis. 88:474-478.
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Progress 01/01/03 to 12/31/03
Outputs
Botrytis cinerea Pers.:Fr. is responsible for a major portion of postharvest decay detected in winter pears in the Pacific Northwest. Currently, the only fungicides registered for postharvest application to pear fruit are thiabendazole and captan. The objectives of this research were (i) to determine the baseline sensitivity levels to benzimidazole (thiabendazole) and dicarboximide (iprodione) fungicides of a wild-type B. cinerea population, and (ii) to determine the influence of fungicide application in the orchard and the packinghouse on sensitivity levels of B. cinerea isolates from pear related sources. Isolates of B. cinerea from commercial orchards not treated with a benzimidazole had significantly lower incidence of resistance (0.59 percent) than isolates from orchards in which benomyl had been applied for experimental purposes (16.0 percent), unsprayed control trees in benomyl sprayed orchards (5.33 percent), and isolates from packinghouses where thiabendazole
was applied as a prestorage drench or line spray (3.23 percent). All isolates from all pear related sources tested were sensitive to ten milligrams per liter iprodione. This study provides evidence supporting current recommendations of a single postharvest application of a benzimidazole to control decay caused by B. cinerea, and avoidance of any benzimidazole containing fungicide in the orchard. The aims of a second study were to examine the sources and population sizes of Botrytis cinerea and Penicillium species in Anjou pear orchards, packinghouses and in storage, and to determine the relationship between population sizes and postharvest decay. Densities of B. cinerea ranged from nondetectable to 4.0 colony forming units per square centimeter on fruit, nondetectable to 3.1 colony forming units (CFU) per liter in orchard air, and nondetectable to 1167 CFU per gram in orchard litter. The majority of packinghouse air and orchard soil samples collected yielded no B. cinerea inoculum.
Densities of Penicillium species ranged from nondetectable to 2.7 CFU per square centimeter on pear fruit, nondetectable to 3.13 CFU per liter in orchard air, nondetectable to 11.8 CFU per liter in packingline air, nondetectable to 3.9 CFU per liter in cold storage air, 38 to 431 CFU per gram in orchard soil, and 131 to 1128 CFU per gram in orchard litter. The mean incidence of gray mold in stored Anjou pear fruit ranged from 0.7 to 10.7 percent. Incidence of blue mold ranged from zero to 16.5 percent. Significant positive correlations were observed between decay and fruit surface populations of B. cinerea and Penicillium species. In conclusion, inoculum levels of these important postharvest pathogens in orchard and packinghouse air, and orchard soil and litter cannot be used as indicators of postharvest decay, whereas the inoculum level on fruit surfaces may be a useful predictor of decay.
Impacts
Our research on resistance of decay fungi has lead to a concerted effort to evaluate new methods of decay control. Several new synthetic fungicides and biological control agents have been evaluated and are approaching EPA registration. In addition, the relationship between populations of decay fungi in the orchard and decay in storage is being validated as a model to predict the risk of decay. New methods will be studied that reduce populations of decay fungi in the orchard. Fruit from high risk orchards can be targeted for short term storage and early marketing, thus reducing losses to both the grower and the packer.
Publications
- Lennox, C.L., and Spotts, R.A. 2003. Sensitivity of populations of Botrytis cinerea from pear related sources to benzimidazole and dicarboximide fungicides. Plant Dis. 87:645-649.
- Lennox, C.L., Spotts, R.A., and Cervantes, L.A. 2003. Populations of Botrytis cinerea and Penicillium spp. on pear fruit and in orchards and packinghouses, and their relationship to postharvest decay. Plant Dis. 87:639-644.
- Spotts, R.A., and Cervantes, L.A. 2003. Populations of Botrytis cinerea on pear fruit and their relationships to stem end gray mold decay. 8th International Congress of Plant Pathology 2:316.
- Gariepy, T.D., J.E. Rahe, C.A. Levesque, R. Spotts, D. Sugar and J.L. Henriquez. 2003. Analysis of putative Neofabraea isolates from bull's eye rot on stored pears from the Pacific Northwest by conventional and molecular methods suggests that N. alba is endemic in western North America. Can. J. Plant Pathol. 25: 109. Abstr.
- Henriquez, J.L., Sugar, D, and Spotts, R.A. 2003. Studies on the etiology and epidemiology of bull's-eye rot of pears. Phytopathology 93 (supplement):S35. Abstr.
- Spotts,R.A., O'Gorman,D.T., Sholberg,P.L. and Chand-Goyal,T. 2003. Partial sequence of the rDNA ITS region of Cystofilobasidium infirmominiatum strain YY6. Published at the National Center for Biotechnology Information website http://www.ncbi.nlm.nih.gov/ (accession AY264716).
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Progress 01/01/02 to 12/31/02
Outputs
d'Anjou pear, the main cultivar grown in the Mid-Columbia region of Oregon is subject to russeting of the fruit surface, resulting in reduced quality and value. The role of Aureobasidium pullulans and Rhodotorula glutinis in russet of pear fruit was studied. Inoculations were done at full bloom and petal fall. Populations of A. pullulans on floral and fruit tissue were monitored during spring in commercial orchards with a history of russet. Russet of fruit in both studies was evaluated at harvest. Inoculation with two strains of each fungus at 10E8 CFU/ml increased russet. Inoculations with 10E4 or 10E6 CFU/ml did not increase russet. In commercial orchards, there was no correlation between fruit russet and the populations of A. pullulans on floral or fruit tissue. Populations were less than 10E3 CFU/g tissue. We conclude that A. pullulans and R. glutinis are not major contributors to russet of d'Anjou pear fruit in the Mid-Columbia region. In a separate study, we
isolated Phytophthora syringae from Granny Smith apples that had been stored at 0 C for three months. Decayed areas were light brown and firm with a slightly indefinite margin. Apples were inoculated with mycelial plugs of P. syringae. Lesions developed at 5 C and 22 C on all inoculated apples but not on noninoculated controls. P. syringae was reisolated from lesions of all infected fruit. This is the first report of postharvest decay of apples by P. syringae in the United States.
Impacts
Elimination of yeasts as causes of russeting of d'Anjou pear fruit allows research to focus on other possible causes. The first report of Phytophthora syringae in stored apples in the Mid-Columbia region is a cause for concern, but less than 1% of the fruit were infected in 1988, 1990, and 1991; and this decay has not been observed since 1991. Thus, no special control measures are necessary at this time.
Publications
- Spotts, R.A., Cervantes, L.A., and Facteau, T.J. 2002. Integrated control of brown rot of sweet cherry fruit with a preharvest fungicide, a postharvest yeast, modified atmosphere packaging, and cold storage temperature. Postharvest Biology and Technology 24:251-257.
- Spotts, R.A., and Cervantes, L.A. 2002. Involvement of Aureobasidium pullulans and Rhodotorula glutinis in russet of d'Anjou pear fruit. Plant Disease 86:625-628.
- Spotts, R.A., and Grove, G.G. 2002. First report of Phytophthora syringae causing rot on apples in cold storage in the United States. Plant Disease 86:693.
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Progress 01/01/01 to 12/31/01
Outputs
The objective of this research was to determine quantitative relationships between incidence of pear fruit decay and inoculum dose of Botrytis cinerea and Penicillium expansum using dry conidia applied to wet or dry pears in a settling tower. On wet fruit, incidence of gray mold fruit rot increased from 0.1 to 83.1 percent as the airborne concentration of B. cinerea conidia increased from 0 to 8.6 spores per liter of air. Significantly less decay occurred in fruit inoculated dry compared to wet, particularly in fruit wounded after inoculation. Incidence of blue mold increased from 1 to 100 percent as the airborne concentration of P. expansum conidia increased from 0.1 to 803.5 spores per liter of air.Blue mold incidence was not affected by fruit wetness or time of wounding relative to inoculation. All regressions of decay incidence versus airborne and surface conidial concentrations were highly significant (P= 0.01). Preharvest application of Flint failed to control
blue mold in stored d'Anjou pear fruit, but CIM (Cryptococcus yeast) and Ziram application gave good control. Fludioxonil, JAN PL-40, and CIM controlled blue mold and gray mold in a postharvest drench application. The percent of Penicillium expansum spores resistant to fludioxonil was less when fludioxonil was mixed with CIM than when Fludioxonil was used alone. An experimental product containing citric acid failed to control blue and gray mold. Vegetable oil (Fruit Shield) and zinc (Flowzin) did not control blue mold, but CIM alone or combined with the oil gave good control. Sanitation (cleaning and fumigation with quaternary ammonium compounds) reduced the level of P. expansum spores in the air and on surfaces in a commercial packinghouse. Spores of Botrytis cinerea in orchard air, litter, and on fruit surfaces are harvest, 2001 were at their lowest level in several years. Preliminary relationships between levels of airborne spores of B. cinerea and P. expansum and stem end decay
were determined. Survival structures (sclerotia) of B. cinerea were found on about 20 percent of infected fruit on the orchard floor, and over 90 percent were still viable in July, 2001. Wild blackberries were not a source of gray mold spores during pear harvest in 2000 and 2001. Germination times for spores of B. cinerea, Mucor piriformis, and P. expansum on pear tissue at 30F were, 37, 97, and over 100 hours, respectively. Blue mold, gray mold, and Mucor rot of d'Anjou pears were lowest in fruit harvested one week before commercial harvest and highest three weeks after commercial harvest.
Impacts
The relationship between inoculum dose of dry, airborne spores and disease incidence will be used in a prediciton model to determine the postharvest decay risk at the time of harvest. The yeast Cryptococcus infirmo-miniatus is currently in the EPA registration process and will provide excellent biocontrol and resistance management.
Publications
- Spotts, R.A. and L.A. Cervantes. 2001. Disease incidence-inoculum dose relationships for Botrytis cinerea and Penicillium expansum and decay of pear fruit using dry, airborne conidia. Plant Disease 85:755-759.
- Spotts, R.A. 2001. Decay-the big picture. Proceed. 17th Ann. Wash. Tree Fruit Postharvest Conference. Wenatchee, March 14, 2001.
- Spotts, R.A. and L.A. Cervantes. 2001. Involvement of Aureobasidium pullulans and Rhodotorula glutinis in russet of d'Anjou pear fruit. Phytopathology 91 (supplement):S83-84.
- Spotts, R.A., L.A. Cervantes, and T.J. Facteau. 2001. Control of brown rot of sweet cherry fruit with a preharvest fungicide, a postharvest yeast, and modified atmosphere packaging. Phytopathology 91 (Supplement):S190.
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Progress 01/01/94 to 12/30/94
Outputs
ORE00426 'Bosc' (Pyrus communis, L.) pears harvested at commercial maturity withflesh firmness (FF) of 75N from the Medford District of Oregon were stored in either air or step-wise low O2 at -1 C during the 1992-3 and 1993-4 seasons. The combination of prestorage heat (28 C for 1 day) and step-wise low oxygen storage effectively reduced side rot by 60 and 63% in 1993 and 1994, respectively. Even greater decay control was obtained with the fungicides imazalil and Exp10412A on inoculated fruit and thiabendazole plus captan on noninoculated fruit. The effects of soil moisture, temperature, and nutrient availability on the population dynamics of Mucor piriformis were studied using moisture levels from -0.1 to -40 kPa, temperatures from -1 to 25 C, and three nutrient levels adjusted with pear juice. All three factors affected the population dynamics of M. piriformis in soil. Few interactions occurred among the factors, and no interactions were observed consistently.
Populations of M. piriformis were higher in soil at -0.1 kPa than in drier soils. Propagule density was highest in soil at 5 and 10 C during the first 30 days of the study but greater at -1 and 5 C during the last 30 days. Propagule density consistently increased as soil nutrient concentration increased. Results are discussed in relation to dynamics of M. piriformis in pear orchard soils.
Impacts
(N/A)
Publications
- SPOTTS, R. A., and L. A. CERVANTES. 1994. Effects of soil moisture, temperature,and nutrient availability on the population dynamics of Mucor piriformis. Mycological Research 93:342-346.
- SPOTTS, R. A., and T. CHAND-GOYAL. 1994. Sclerotinia rot of pears in Oregon. Phytopathology 84:1102.
- SPOTTS, R. A., and P. G. SANDERSON. 1994. The postharvest environment and biological control. Pages 43-56. In: Biological control of postharvest diseases - theory and practice. C. L. Wilson and M. E. Wisniewski, eds. CRC Press, Inc., Boca R CHAND-GOYAL, T., and R. A. SPOTTS. 1994. A standard method for studying the microbial ecology of fruits. Phytopathology 84:1083.
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Progress 01/01/93 to 12/30/93
Outputs
Short-term low O(subscript 2) storage of `d'anjou' pears to control superficial scald disorder as influenced by CO(subscript 2) levels. Treatments of `d'Anjou" pears (Pyrus communis, L.) with 0.5% O(subscript 2) (1 month) plus 1.0% O(subscript 2) (2 months) suppressed superficial scald effectively if the CO(subscript 2) level was at 0.5%. Treated fruit were scald free within 2 months of holding in air at -1(degree)C. If the CO(subscript 2) level in the storage was minimal (<0.03%), only the continuous 0.5% O(subscript 2) treatment for 2 or 3 months was capable of controlling scald after fruit had been returned to air storage for 2 months. An initial 2-week treatment with high CO(subscript 2) (12%) followed by regular CA storage (2% O(subscript 2) / 1% CO(subscript 2)) for 2.5 months did not suppress scald effectively. The promising short-term low O(subscript 2) regimes for the control of superficial scald of `d'anjou' pears are: 1) 0.5% O(subscript 2) (<0.03%
CO(subscript 2)) for 3 months; and 2) 0.5% O(subscript 2) (1 month) - 1.0% O(subscript 2) (2 months) with CO(subscript 2) at 0.5%.
Impacts
(N/A)
Publications
- CHEN, P.M., VARGA, R.J., and XIAO, Y.Q., 1993. Inhibition of (alpha)-farnesene biosynthesis and its oxidation in peel tissue of `d'Anjou' pears by low-O(subscript 2)/elevated CO(subscript 2) atmospheres. Postharvest Biol. & Tech. 3:215-223.
- KOCA, R.W., HELLICKSON, M.L., and CHEN, P.M., 1993. Mass transfer from `d'Anjou' pears in CA storage. J. Amer. Soc. Agric. Eng. 36:821-826.
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