Robert Crassweller, Ph.D.

Professor of Horticulture

    Expertise:

    Deciduous Tree Fruit Production
    Tree Fruit Rootstocks
    Pruning and Training Tree Fruit
    Apple Varieties
    Tree fruit nutrition
    Asian pear varieties
    Impact of climate change on tree fruit production

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    About Me

    Extension Programs

    As state Extension Specialist for Tree Fruit my duties include developing educational programs for fruit growers throughout the state. I am also in charge of the annual Mid-Atlantic Fruit and Vegetable Conference fruit program for the commercial fruit growers in the region. This program is held annually at the Hershey Convention Center and has attendance from Delaware, Pennsylvania, Maryland, New Jersey, Virginia and West Virginia. Other extension duties include acting as co-leader of the tree fruit and wine grape extension team, coordinating the state wide program in extension for tree fruit, the plant and soil analysis recommendations for tree fruit, pesticide and cultural recommendations for the tree fruit plantings at the Horticultural Research Farm, and Horticultural Section chair for the Pennsylvania Commercial Tree Fruit Production Guide and Horticultural coordinator of the 2016-17 production guide. I am also currently the Editor of The Pennsylvania Fruit News.

    Links

    Resident Instruction

    • HORT 432, Tree Fruit Production.

    Research Interests

    • Tree fruit rootstock evaluation as part of NC-140 research project
    • Tree training and pruning systems
    • Apple cultivar evaluation including disease resistant cultivars
    • Wine grape cultivar evaluation as part of NE-1020 research project

    Professional Associations

    • Treasurer American Pomological Society, 1990 to present
    • Business Manager American Pomological Society, 1990 to present
    • Editor, Pennsylvania Fruit News March, 1987 to present
    • State Horticultural Association of Pennsylvania Executive Board (ex-officio), 1984 to present
    • American Pomological Society, 1980 to present
    • American Society for Horticultural Science, 1977 to present
    • International Society for Horticultural Science, 1992 to present

    Recent Publications

    • Marini, R., W. Autio, B. Black, J. Cline, W. Cowgill, R. Crassweller, P. Domoto, C. Hampson, R. Moran, R. Quezada, T. Robinson, D. Ward, D. Wolfe. 2013. Return bloom on Golden Delicious apple trees as a affected by previous season's crop density on three rootstocks at 11 locations. J. of the American Pomological Society. 67:80-88.
    • Hoover, E., R. Marini, E. Tepe, W. Autio, A. Biggs, J. Clemens, R. Crassweller, D. Foster, M. Foster, P. Hirst, D. Miller, M. Parker, G. Peck, J. Racsko, T. Robinson, M. Warmund. 2012. eApples: A Case Study in Using eXtension.org to Increase Access to Research-Based Information. HortTechnology 22:576-579.
    • Jensen, P., N. Halbrendt, G. Fazio, I. Makalowska, N. Altman, C. Praul, S. Maximova, H. Ngugi, R. Crassweller, J. Travis, T. McNellis. 2012. Rootstock-regulated gene expression patterns associated with fire blight resistance in apple. BMC Genomics 13:9 see http://www.biomedcentral.com/content/pdf/1471-2164-13-9.pdf
    • Harper, J., A. Jimenez-Maldonado, R. Crassweller, D. Smith. 2013. Impact of producer risk preferences on selection of fresh-market apple training systems. Int. J. Fruit Sci. 13:265-273.

    • Marini, R. P.; Autio, W. R.; Black, B.; Cline, J. A.; Cowgill, W., Jr.; Crassweller, R.; Domoto, P.; Hampson, C.; Moran, R.; Parra-Quezada, R. A.; Robinson, T.; Stasiak, M.; Ward, D. L.; Wolfe, D. 2012. Summary of the NC-140 apple physiology trial: The relationship between Golden Delicious fruit weight, crop density at 12 locations as influenced by three dwarfing rootstock. Journal of the American Pomological Society, 2012, 66, 2, pp 78-90.

    • Marini, R. P.; Autio, W. R.; Black, B.; Cline, J.; Crassweller, R. M.; Domoto, P. A.; Hampsen, C.; Moran, R.; Quezada, R. A.; Robinson, T.; Stasiak, M.; Wolfe, D. 2012. The influence of crop density on annual trunk growth of Golden Delicious apple trees on three rootstocks at 11 locations. Journal of the American Pomological Society, 2012, 66, 4, pp 183-195.
    • Autio, W. T., Robinson, B. Black, T. Bradshaw, J. Cline, R. Crassweller, C. Embree, E. Hoover, S. Hoying, K. Iungerman, R. Johnson, G. Lang, M. Parker, R. Perry, G. Reighard, M. Stasiak, M. Warmund and D. Wolfe. 2011. Performance of Fuji and McIntosh apple trees after 10 years as affected by several semidwarf rootstocks in the 1999 NC-140 apple rootstock trial. J. Amer. Pom. Soc. 65:2-20.
    • Autio, W. T., Robinson, B. Black, T. Bradshaw, J. Cline, R. Crassweller, C. Embree, E. Hoover, S. Hoying, K. Iungerman, R. Johnson, G. Lang, M. Parker, R. Perry, G. Reighard, M. Stasiak, M. Warmund and D. Wolfe. 2011. Performance of Fuji and McIntosh apple trees after 10 years as affected by several semidwarf rootstocks in the 1999 NC-140 apple rootstock trial. J. Amer. Pom. Soc. 65:21-38.
    • Kelley, J. Hyde, J. Travis, R. Crassweller. 2010. Assessing consumer preferences of scab-resistant apples: A sensory evaluation. HortTechnology. 20:885-891.

    • Robinson, T., L. Anderson, W. Autio, B. Barrit, J. Cline, W. Cowgill, R. Crassweller, C. Embree, D. Ferree, E. Garcia, G. Greene, C. Hampson, K. Kosola, M. Parker, R. Perry, T. Roper, M. Warmund. 2007. A multi-location comparison of Geneva 16, Geneva 41 and M.9 apple rootstocks in North America. Acta Hort. 732:59-65. http://www.actahort.org/books/732/732_4.htm

    • Philip J. Jensen xIzabela Makalowska x Naomi Altman x Gennaro Fazio x Craig Praul x Siela N. Maximova x Robert M. Crassweller x James W. Travis x Timothy W. McNellis. 2009. Rootstock-regulated gene expression patterns in apple tree scions. Tree Genetics & Genomes. 6:57-72.

    • Marini, R., B. Black, R. Crassweller, P. Domoto, C. Hampson, S. Johnson, K. Kosola, S. McArtney, J. Masabni, R. Moran, R. Quesada, T. Robinson and C. Rom. 2009. Performance of Golden Delicious apple on 23 rootstocks at 12 locations: A five-year summary of the 2003 NC-140 dwarf rootstock trial. J. Amer. Pom. Soc. 63:115-127

    • Autio, W., T. Robinson, B. Barritt, J. Cline, R. Crassweller, C. Embree, D. Ferree, E. Garcia, G. Greene, E. Hoover, S. Johnson, K. Kosola, J. Masabni, M. Parker, R. Perry, G. Reighard, S. Seeley and M. Warmund. 2005. Performance of 'Fuji' and 'McIntosh' apple trees after 5 years as affected by several semidwarf rootstocks in the 1999 NC-140 rootstock trial. J. Amer. Pom. Soc. 59(4):192-201.

    • Autio, W.R., T.L. Robinson, B.H. Barritt, J.A. Cline, R.M. Crassweller, C.G. Embree, D.C. Ferree, M.E. Garcia, G.M. Greene, E.E. Hoover, R.S. Johnson, K. Kosola, J. Masabni, M.L. Parker, R.L. Perry,G.L. Reighard, S.D. Seeley, and M. Warmund. 2005. Fuji and McIntosh apple tree performance after 5 years as affected by several dwarfing rootstocks in the 1999 NC-140 Rootstock Trial. Journalof the American Pomological Society 59: 202-214.

    • Marini, R.P., J.L. Anderson, W.R. Autio, B.H. Barritt, J. Cline, W.P. Cowgill, Jr., R. Crassweller, R.M. Garner, A. Gauss, R. Godin, G.M. Greene, C. Hampson, P. Hirst, M.M. Kushad, E. Mielke, R. Moran, C.A. Mullins, M. Parker, R.L. Perry, J.P. Privé, G.L. Reighard, T. Robinson, C.R. Rom, T. Roper, J.R. Schupp, E. Stover, and R. Unrath. 2006. Performance of 'Gala' on 18 dwarfing rootstocks: Ten-year summary of the 1994 NC-140 rootstock trial. Journal of the American Pomological Society 60:69-83.

    • Crassweller, R., R. McNew, A. Azarenko, B. Barritt, R. Belding, L. Berkett, S. Brown, J. Clemens, J. Cline, W. Cowgill, D. Ferree, E. Garcia, D. Greene, G. Greene, C. Hampson, I. Merwin, S. Miller, D. Miller, R. Moran, J. Obermiller, D. Rosenberger, C. Rom, T. Roper, J. Schupp and E. Stover. 2005. Performance of apple cultivars in the 1995 NE-183 regional project planting: I. Growth and yield characteristics. J. Amer. Pom. Soc. 59:18-27.

    • Miller, S., C. Hampson, R. McNew, L. Berkett, S. Brown, J. Clemens, R. Crassweller, E. Garcia, D. Greene, G. Greene. 2005. Performance of apple cultivars in the 1995 NE-183 regional project planting: III. Fruit sensory characteristics. 2005. J. Amer. Pom. Soc. 59:28-43.
    • Miller, S., R. McNew, B. Barritt, L. Berkett, S. Brown, J. Cline, J. Clemens, W. Cowgill, R. Crassweller, E. Garcia, D. Greene, G. Greene, C. Hampson, I. Merwin, D. Miller, R. Moran, C. Rom, T. Roper, J. Schupp and E. Stover. 2005. Effect of cultivar and site on fruit quality as demonstrated by the NE-183 regional project on apple cultivars. HortTechnology 15:886-895.
    • Greene, D. A. Azarenko, B. Barritt, R. Belding, L. Berkett, J. Cline, W. Cowgill, R. Crassweller, D. Ferree, E. Garcia, G. Greene, C. Hampson, R. McNew, I. Merwin, D. Miller, S. Miller, R. Moran, M. Parker, D. Rosenberger, C. Rom, T. Roper, J. Schupp and E. Stober. 2004. Multidisciplinary evalutation of new apple cultivars: The NE-183 regional project. J. Amer. Pom. Soc. 58:61-64.
    • Miller, S., R. McNew, R. Belding, L. Berkett, S. Brown, J. Clemens, J. Cline, W. Cowgill, R. Crassweller, D. Ferree, E. Garcia, D. Greene, G. Greene, C. Hampson, I. Merwin, R. Moran, T. Roper, J. Schupp and E. Stover. 2004. Performance of apple cultivars in the 1995 NE-183 regional project planting: II. Fruit quality characteristics. J. Amer. Pom. Soc. 58:65-77.
    • Crassweller, R. M. and D. E. Smith. 2004. Will high density work for processing apples. Acta Horticulturae 636:661-666.
    • Crassweller, R. M. and D. E. Smith 2003. Apple cultivar sensitivity to azoxystrobin fungicide. J. Amer. Pom. Soc. 57:166-168.
    • Harper, J. K., R. M. Crassweller, D. E. Smith. 2002. Impact of apple rootstock/cultivar on processing market profitability. J. Amer. Pomological Society. 56:112-117.
    • Crassweller, R. M. 2001. Apple variety development - NE-183 and Beyond. PA Fruit News 81(4):24-27.
    • Crassweller R. M. 2001. ReTain™ a harvest management tool. In Proceedings of Penn State Cooperative Extension Fruit School on Plant Growth Regulators. W. C. Kleiner L. Roth eds. Pgs. 12.1-12.6.
    • Crassweller, R. M. 2001. The basics on thinning chemicals for apples. In Proceedings of Penn State Cooperative Extension Fruit School on Plant Growth Regulators. W. C. Kleiner L. Roth eds. Pgs 1.1 - 1.9
    • Crassweller, R. M., D. E. Smith, and L. D. Tukey. 2001. Performance of 'Golden Delicious' and 'Delicious apples on dwarfing rootstocks. Acta Horticulturae 557:47-54.
    • Hirst, P. M., W. R. Autio, J. A. Barden, G. R. Brown, R. M. Crassweller, P. A. Domoto, and J. R. Schupp. 2001. Performance of trees in the 1990 NC-140 apple cultivar rootstock planting: Additional cultivars and rootstocks. J. Amer. Pom. Soc. 55:178-184.
    • Autio, W. R., J. L. Anderson, J. A. Barden, G. R. Brown, R. M. Crassweller, P. A. Domoto, A. Erb, D. C. Ferree, A. Gaus, P. M. Hirst, C. A. Mullins, J. R. Schupp. 2001. Location affects performance of Golden Delicious, Jonagold, Empire, and Rome Beauty Apple Trees on five rootstocks over ten years in the 1990 NC-140 cultivar rootstock trial. J. Amer. Pom. Soc. 55:138-145.
    • Autio, W. R., J. L. Anderson, J. A. Barden, G. R. Brown, R. M. Crassweller, P. A. Domoto, A. Erb, D. C. Ferree, A. Gaus, P. M. Hirst, C. A. Mullins, J. R. Schupp. 2001. Performance of Golden Delicious, Jonagold, Empire, and Rome Beauty Apple Trees on five rootstocks over ten years in the 1990 NC-140 cultivar rootstock trial. J. Amer. Pom. Soc. 55:131-137.
    • Crassweller, R. M., J. W. Travis, D. E. Smith. 2000. Nutritional methods to reduced fire blight susceptibility. PA Fruit News 80(4):14, 16.
    • Crassweller, R. M., D. E. Smith and K. Myung. 2000. Improving production efficiency of York Imperial by determining flowering and spur characteristics. PA Fruit News 80(4):10, 12, 14. NC-140. 2000. Performance of 'Gala' apple on 18 dwarf rootstocks: A Five year summary of the 1994 NC-140 dwarf rootstock trial. Journal of the American Pomological Society (in press)
    • Koc, A. B., P. H. Heinemann, R. M. Crassweller. 2000. Automated cycled sprinkler irrigation system for frost protection of apple buds. Applied Engineering in Agriculture. 16:231-240.
    • Crassweller, R. M., D. E. Smith. 1999. Apple training system trials - 1998. PA Fruit News. 79(2):76-78.
    • Crassweller, R. M., D. E. Smith and J. E. Griggs. 1999. Establishment of 1998 NC-140 Sweet Cherry rootstock planting. PA Fruit News. 79(3):43-44. Smith, D. E., R. M. Crassweller. 1999. The use of ReTain to reduce drop and improve color and size of McIntosh, and Golden Delicious apples. PA Fruit News. 79(3):37-42.
    • Crassweller, R. M. 1998. Señalmientos acerca de la polinización para incrementar la cosecha de manzanas. Memorias Simposium Internacional sobre Apicultura y Polinización. 20 February, Cuauhtemoc, México. Sponsored by Centro de Investigación en Alimentacion y Desarrollo. pg 5-11.
    • Greene II*, G.M., J.K. Harper, W.J. Kleiner and R.M. Crassweller. Jan. 9, 1998. A horticulturist's view of the economics of apple production systems. Illinois Speciality Growers Convention. Pheasant Run Resort, St. Charles, IL.
    • Crassweller, R. M. (ed.) 1997. Small Scale Fruit Production Guide. Penn State University College of Agricultural Sciences. 178 pp.
    • Barden, C., and R. M. Crassweller. 1997. Good manufacturing practices for Pennsylvania cider. PA Fruit News 77(7):25-28, 31-32.
    • Crassweller, R. M. 1997. What's happening electronically. PA Fruit News 77(6):6,8.
    • Greene, G. M., W. C. Kleiner, R. M. Crassweller. 1997. Influence of rootstocks on the growth, productivity and longevity of apples (Report of 1996 Research). PA Fruit News 77(2):71-74.
    • Crassweller, R. M. 1996. Peach survey results. Pa Fruit News. 76(3):27-28.
    • Crassweller, R. M. 1996. 137th Annual Meeting. Pa Fruit News. 76(3):6.
    • Crassweller, R. M. 1996. A call from the future. PA Fruit News. 76(4):6,8.
    • Crassweller, R. M. 1996. Can it be done. Pa Fruit News. 76(5):4, 6.
    • Crassweller, R. M. 1996. The effects of summer pruning on apples and peaches. PennPages #2940143 (revised)
    • Crassweller, R. M. 1996. References Materials for Fruit Production. PennPages #29401262 (revised)
    • Crassweller, R. M. 1996. Pear maturity indices. PennPages #2940149 (revised)
    • Crassweller, R. M. 1996. Orchard site selection. PennPages #29401147 (revised)
    • Crassweller, R. M. 1996. Identifying apple and other fruit varieties. PennPages #29401160 (revised)
    • Crassweller, R. M. 1996. Whose land is it? Pa Fruit News. 76(8):6,8.
    • Crassweller, R. M. 1996. Long range planning. Pa Fruit News. 76(7):4,6.
    • Crassweller, R. M. and D. E. Smith. 1996. Influence of training systems on tree size, yield, and fruit quality of 15 peach cultivars. HortSci. 31:666. (abstr.)
    • Crassweller, R. M, D. E. Smith, L. D. Tukey. 1996. Yields of Mature Apple Trees on Various Rootstocks. Proceedings of the 71st Cumberland Shenandoah Fruit Workers Conference.
    • Rajotte, E. G., R. M. Crassweller, J. W. Travis. 1996. Pennsylvania Tree Fruit Production Guide. The Pennsylvania State University. 246 pp.
    • NC-140.1996 Performance of the NC-140 Cooperative apple rootstock planting: I. Survival, tree size, yield and fruit size. Fruit Var. J. 50:6-11.
    • NC-140.1996. Performance of the NC-140 Cooperative apple rootstock planting: II. A 10 - year summary of TCA, Yield and Yield efficiency at 31 sites. Fruit Var. J. 50: 11-18.
    • NC-140. 1996. Horticultural characteristics of 'Starkspur Supreme Delicious' apple on 15 rootstocks at 24 sites. Fruit Var. J. 50: 18-24
    • Crassweller, R. M. 1995. High density and processing - Do they mix? Compact Fruit Tree 28:43-47.
    • Crassweller, R. M. 1995. Choosing a nursery for fruit trees. PennPages #2940113 (revised)
    • Heinemann, P. H., Z. A. Varghese, C. T. Morrow, H. J. Sommer III, R. M.
    • Crassweller. 1995. Machine vision inspection of 'Golden Delicious' apples. Applied Engineering in Agriculture. 11(6):901-906.
    • Crassweller, R. M. 1994. The winter of 93-94 - One to remember. PA Fruit News 74(4):4,6.
    • Crassweller, R. M. 1994. Does anyone care about production information? PA Fruit News 74(7):6,8.
    • Crassweller, R. M. 1994. Who should be the audience? PA Fruit News 74(8):6,8.
    • Crassweller, R. M. 1994. Accentuate the positive. PA Fruit News 74(10): 4, 6
    • Crassweller, R. M. 1994. Designing a fruit extension program. PA Fruit News 74(11): 4, 6.
    • Heisey, L.W., P.H. Heinemann, C.T. Morrow, R.M. Crassweller. 1994. Automation of an intermittent overhead irrigation frost protection system for an apple orchard. Appl. Engin. in Agr. 10:669-675;
    • Crassweller, R.M., J.W. Travis, P.H. Heinemann and E.G. Rajotte. 1993. The actual and potential future use of expert system technology in horticulture. Hort. Technology 3:203-205;
    • C.M. Werner, R.M. Crassweller, T.E. Clark. 1993. Cold hardiness of peach stem tissue over two dormant seasons. Fruit Varieties Journal 47:72-79;
    • Crassweller, R.M., G.M. Greene II, S.S. Miller and V. Eby. 1993. A chemical thinning expert system on the Penn State Apple Orchard Consultant expert system. Acta Horticulturae. 313:215-218;
    • Crassweller, R.M., J.W. Travis, E.G. Rajotte, J. McClure, and P.H. Heinemann. 1993. Building expert systems for use by commercial farmers. Acta Horticulture 313:205-208
    • Brown, K., P Hammer, R Crassweller, G Greene, L Lehman-Salada 1993 Predicting firmness of 'York Imperial' apples after long-term storage. HortTechnology 3: 318-322.
    • Travis, J. W., E. Rajotte, R. Bankert, K. D. Hickey, L. A. Hull, V. Eby, P. H. Heinemann, R. Crassweller, J. McClure, T. Bowser, and D. Laughland. 1992. A working description of the Penn State Apple Orchard Consultant, an expert system. Plant Disease. 76:545-554.
    • Crassweller, R. M. and G. M. Greene. 1991. 1990 Evaluation of cultivars for maturity development and storage potential. PA Fruit News. 71(2):35-39.
    • Crassweller, R. M., H. L. Braun, T. A. Baugher, G. M. Greene II, and R. A. Hollander. 1991. Color evaluations of 'Delicious' strains. Fruit Var. J. 45:114-120.
    • Crassweller, R. M. and S. J. Wallner. 1991. The Pennsylvania State University: A commitment to the land-grant philosophy. HortScience. 26: 618, 624.
    • Crassweller, R. M. and G. M. Greene and S. S. Miller. 1991. A decision support system for chemical thinning of apples. Proc. 67th Cumberland Shenandoah Fruit Workers Conference.
    • Greene, G. M. and R. M. Crassweller. 1991. 1992 Pennsylvania apple calcium spray recommendations. Proc. 67th Cumberland Shenandoah Fruit Workers Conference.
    • Heinemann, P. H., C. T. Morrow, J. D. Martsolf, R. M. Crassweller, and K. B. Perry. 1991. A decision support program for the design and management of frost protection systems. Proc. 67th Cumberland Shenandoah Fruit Workers Conference.
    • Heinemann, P. H., C. T. Morrow, J. D. Martsolf, R. M. Crassweller, and K. B. Perry. 1991. A decision support program for the design and management of frost protection systems. Proc. 67th Cumberland Shenandoah Fruit Workers Conference.
    • Crassweller, R. M. and G. M. Greene. 1990. Evaluation of cultivars for processing storage potential. Pa Fruit News 70(2):26,28-34.
    • Crassweller, R. M., V. Esh, and J. W. Travis. 1990. An expert system for selecting peach and nectarine cultivars. HortScience 25:1449.
    • Crassweller, R. M., J. W. Travis, P. H. Heinemann and E. G. Rajotte. 1990. Commercial applications of expert systems in apple production. HortScience 25: 1176
    • Crassweller, R. M., and S. J. Wallner. 1990. Pennsylvania - The keystone of horticulture. HortScience 25:1462,1699.
    • Crassweller, R. M., P. H. Heinemann, and E. G. Rajotte. 1989. An expert system on a microcomputer for determining apple tree spacing. HortScience 24:148.
    • Crassweller, R. M. and R. A. Hollander. 1989. Consumer evaluations of 'Delicious' apple strains. Fruit Varieties Journal. 43:139-142.

    Background

    Education
    Ph.D., Horticulture, Ohio State University, 1980 M.S., Horticulture, Ohio State University, 1978 B.S., Botany, Miami University, 1976