Source: VIRGINIA POLYTECHNIC INSTITUTE submitted to NRP
MANAGEMENT OF DISEASES OF TREE FRUITS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0206172
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Apr 1, 2006
Project End Date
Sep 30, 2012
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
VIRGINIA POLYTECHNIC INSTITUTE
(N/A)
BLACKSBURG,VA 24061
Performing Department
ALSON H. SMITH, JR AGRI RES & EXT CENTER
Non Technical Summary
More than 30 diseases of economic importance affect tree fruits in Virginia. Annual disease losses on apples and stone fruits are affected by weather conditions and may vary widely from orchard to orchard and from region to region within the state. Several diseases can cause losses of more than 90% in poorly controlled disease situations. Monitoring of threatening diseases, improving cultural control practices, and timely application of fungicides have provided acceptable management programs for many of these diseases. Ongoing evaluations of fungicides, bactericides, and biocontrol agents are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. Actual impacts of this project are expected to result in reduced pesticide use, retention of fruit yield and quality, efficient use patterns for new pesticides, and continued viability of Virginia's fruit industry. It is estimated that contributions of this project will reduce pesticide usage by 10% and annual disease losses to no more than 5%. If one considers the potential loss of yield and profitability in just 10% of Virginia's orchards and allied businesses, offsetting these yield and quality losses related to fungicide limitations could have a potential financial impact exceeding $10 million dollars. The purpose of this project is to develop and maintain safe, reliable, effective, economical programs for management of tree fruit diseases in Virginia's orchards and postharvest fruit storages.
Animal Health Component
80%
Research Effort Categories
Basic
5%
Applied
80%
Developmental
15%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2121110116080%
2121114116010%
2121119116010%
Knowledge Area
212 - Pathogens and Nematodes Affecting Plants;

Subject Of Investigation
1114 - Peach; 1119 - Deciduous tree fruits, general/other; 1110 - Apple;

Field Of Science
1160 - Pathology;
Goals / Objectives
1. Develop effective, economical programs for in-orchard management of diseases, including: scab, rusts, powdery mildew, and summer diseases of apple and brown rot, scab, and mildews of peach, and fireblight of apple. 2. Develop reliable controls for postharvest diseases of apple, peach and nectarine. 3. Monitoring of resistance to commercial fungicides in populations of pathogenic fungi in orchards, including: a.) apple scab, and b.) bitter rot (Colletotrichum sp.) and other summer diseases of apple, peach and nectarine.
Project Methods
Objective 1: The effectiveness of fungicides, bactericides and biocontrol agents will be evaluated on target diseases on fruit and foliage and degree of phytotoxicity on apple, peach and nectarine. Diseases emphasized will be scab, powdery mildew, rusts, fireblight and summer diseases of apple, and leaf curl, brown rot, scab and mildews of peach. Materials will be applied as dilute sprays or as concentrate sprays with a commercial airblast sprayer using published techniques for apple and peach. Initial application rates will be selected and adjusted to approach the threshold of efficacy based on background information and previous results. Appropriate controls will be included in each test. Where appropriate, disease inoculum will be placed in the test trees. Apple foliage will be scored for disease incidence, leaf area infected, and lesions per leaf. Fruit will be rated after harvest for percent fruit diseased and graded for fruit finish. Fireblight studies will involve blossom and shoot blight phases of the disease. Replicated, artificially inoculated tests plots will be established on mature trees. Natural blight infection periods will be recorded. Treatment effectiveness will be determined by comparing percent susceptible blossoms, percent flower clusters infected, percent control, percent shoots infected and shoot canker length. Disease control and phytotoxicity data will be analyzed statistically as indicated above. Objective 2: Effects of pre-harvest and postharvest treatments will be evaluated by established methods. Replicated apple and peach tests will include untreated controls, standard and experimental treatments. Fruit free of apparent decay will be treated, then examined for disease incidence at regular intervals to determine the period of residual effectiveness. Fruit will be incubated in commercial cold storage to allow natural infection by the inoculum present in the room. Disease control and phytotoxicity data will be analyzed by analysis of variance and the means compared by the Waller-Duncan k-ratio t-test or other appropriate procedures. Percentage data will be transformed by the appropriate transformation (e.g. arcsin or square root transformation) before analysis. Objective 3: To test for possible shifts in sensitivity toward resistance, sterol-inhibiting fungicide-related treatments will be included in test areas where resistance may be building up or in suspect commercial orchards in early season treatments. The basis for determining resistance will be differential mycelial growth on selected rates of the active ingredient in potato dextrose agar (PDA. We will also monitor for resistance to other fungicide classes and explore the use of PCR-based methods for strobilurin resistance, if that is indicated. To test for possible shifts in sensitivity toward resistance of the summer diseases to the strobilurin fungicides, isolates of pathogenic fungi will be collected from orchards where resistance may be building up. The basis for determining resistance will be differential mycelial growth on the strobilurin toxicant in PDA. Tests will be repeated to accommodate analysis of variance of the results.

Progress 04/01/06 to 09/30/12

Outputs
OUTPUTS: Apple disease management research during the 6-yr project period focused on evaluation of experimental compounds for broad-spectrum fungal disease management, for offsetting fungicide resistance, and on testing new materials for managing fire blight. In 2006-12, fungicide testing on apples and peaches included 126 tests of 1,091 treatments. During this period fungicide resistance increased in both apple scab and powdery mildew. Sterol-inhibiting (SI) fungicides had been valued previously for their after-infection control of scab, powdery mildew, and rusts; but the relative commercial value of these compounds has been compromised by development of resistance in the scab and mildew fungi in some Virginia orchards. In 2007, graduate student S. C. Marine identified high levels of SI resistance in populations of Venturia inaequalis, indicating that replacement programs were needed. The strobilurin (QoI) fungicides became the primary SI replacements for scab and mildew control, but in 2011 she also confirmed scab fungus resistance to the QoIs. Since 2009 we have also observed declining control of apple powdery mildew by SIs and QoIs in our research plots compared to control 17 years ago. Based on percent of treated and non-treated leaves infected, control by the SI myclobutanil declined from 90 percent in 1994 to less than 15 percent in 2010, and mildew control by QoIs declined from the 85 percent level down to as low as 30 percent by trifloxystrobin. In 2008-11, several combination products or tank-mixes showed promise for management of SI-resistant scab and other important diseases. Luna Sensation (a package mix of fluopyram and trifloxystrobin) and Merivon (a mix of fluxopyroxad and pyraclostrobin) gave excellent control of powdery mildew and scab, as well as summer diseases. However, in the face of QoI resistance in scab in 2012, Luna Tranquility (a package mix of fluopyram and pyrimethanil) was more effective than Luna Sensation. Flutriafol (Topguard), although an SI triazole fungicide, gives good mildew control, and myclobutanil and flutriafol give excellent quince rust and cedar-apple rust control. Topguard, Luna Sensation, Merivon, and Luna Tranquility suppress the sporulation of overwintering primary powdery mildew shoots, a prerequisite for aggressive seasonal management. Mancozeb, ziram and captan continue to show utility as the primary mixing partners to offset development of resistance to "at-risk" fungicide classes in scab, but sulfur remains the chief fungicide to fill this role for mildew. Pristine (pyraclostrobin + boscalid) gives excellent control of late season diseases. Fludioxonil (Scholar) applied as a postharvest dip treatment, controls bitter rot, white rot and Alternaria rot as well as Penicillium blue mold. Because the supply of active chemical classes of fungicides is limited and development of resistance to many of them is likely, a top priority of this project has been to test new chemistries and integration of these with economical cultural management practices to offset development of resistance among the 10-15 diseases that are an ongoing threat to quality apple production in Virginia and the mid-Atlantic region. PARTICIPANTS: Individuals who worked on the project included research and extension scientists and state and privately sponsored technical staff and county agricultural agents. Clientele include county and regional agricultural agents and consultants and the end users who primarily include commercial and home fruit growers. Each year there were approximately 40 opportunities for training among one or more of these groups. Meetings were organized to meet the joint needs of several related groups including training for extension agents at in-orchard meetings for growers, pest management scouts and agents. These meetings regularly provided in-depth honing of disease, insect and horticultural problem diagnostic skills. TARGET AUDIENCES: The primary target audiences were commercial and home fruit growers and their advisors. PROJECT MODIFICATIONS: During the report period there was increased emphasis placed on web-based approaches, including regular posting of disease updates during the growing season on the blog at: http://treefruitdisease.blogspot.com/

Impacts
Relevant findings involving registered compounds provide revision input for the popular Spray Bulletin for Commercial Tree Fruit Growers which is annually utilized through more than 40,000 web hits and down-loads as well as the traditional printed copies. Results were published in Plant Disease and on-line through Plant Disease Management Reports, and presented at national and regional scientific and commercial production meetings. The potential for resistance by several important diseases to several fungicide classes, the need to manage ten or more diseases, and varying disease pressure from year to year across fruit-growing regions of Virginia underscore the need for ongoing testing of new materials and novel approaches for economical, environmentally sensitive tree fruit disease management. Ongoing fungicide and bactericide evaluations are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. Web-based presentation of research findings and in-orchard extension agent and grower training represent useful forms of outcome assessment. New findings particularly relevant to the Virginia and mid-Atlantic fruit industry were presented at winter and in-orchard meetings with fruit growers. Starting in March 2010 tree fruit disease management information was posted on a blog targeting the Winchester, VA area and the blog: http://treefruitdisease.blogspot.com/ had more than 10,000 pageviews from 95 different countries since its inception. Approximately half of those were from 49 states in the U. S. and 55% of the site visits were from Virginia or West Virginia.

Publications

  • Miller S., K. Yoder. 2011. Chemical and Cultural Approaches to Enhancing Host Resistance to Fire Blight: Plant Growth Regulators. Pp. 249-255 in Fire Blight; History, Biology and Management. T. van der Zwet, N. Orolaza-Halbrendt and W. Zeller eds. APS Press. St. Paul MN. 421 pp.
  • Marine, S. C. D. G. Schmale III, and K. Yoder. 2012. First Report of Reduced Sensitivity to a QoI Fungicide in Apple Scab (Venturia inaequalis) in Virginia and Maryland. Plant Disease 96:1376. http://dx.doi.org/10.1094/PDIS-03-12-0246-PDN
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer, G. Engelman. Management of powdery mildew and other diseases by experimental fungicides and mixed schedules on Idared apples, 2011. Plant Disease Management Reports 6: PF032. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/PF0 32.pdf
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer, G. Engelman. Evaluation of experimental fungicides and mixed schedules on Stayman, Idared, and Ginger Gold apples, 2011. Plant Disease Management Reports 6:PF035. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/PF0 35.pdf
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer, G. Engelman. Early season disease management with experimental fungicides on Red Delicious, Golden Delicious, and Rome apples, 2011. Plant Disease Management Reports 6:PF036. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/PF0 36.pdf
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer, G. Engelman. Early season disease control by protectant fungicides on Nittany apple, 2011. Plant Disease Management Reports 6:PF037. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/PF0 37.pdf
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer, G. Engelman. Evaluation of experimental and registered cover spray fungicides for disease control on Fuji apple, 2011. Plant Disease Management Reports 6:PF034. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/PF0 34.pdf
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer, G. Engelman. Evaluation of disease control by lime sulfur applications timed for bloom thinning of Ginger Gold apple, 2011. Plant Disease Management Reports 6:PF038. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/PF0 38.pdf
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer. Suppression of fire blight blossom blight by experimental and registered compounds on Idared apple, 2011. Plant Disease Management Reports 6: PF031. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/PF0 31.pdf
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer, G. Engelman. Evaluation of experimental fungicides for disease control on Loring peach and Redgold nectarine, 2011. Plant Disease Management Reports 6:STF002. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/STF 002.pdf
  • YODER K., A. Cochran II, W. Royston, Jr., S. Kilmer, G. Engelman. Control of scab and brown rot by tetraconazole and febuconazole on Redhaven peach, 2011. Plant Disease Management Reports 6:STF001. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2012/STF 001.pdf


Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Apple disease management research in 2011 focused on evaluation of 12 experimental materials for broad-spectrum fungal disease management and strategies for avoiding development of fungicide resistance. These included 19 tests of 159 treatments on apples or peaches. Sterol-inhibiting (SI) fungicides have been valued in the past for after-infection control of scab, rusts and powdery mildew; however, the relative commercial value of these compounds has been compromised by development of resistance in the scab and mildew fungi in some Virginia orchards. Previously, graduate student S. C. Marine, in cooperation with Dr. D. G. Schmale, identified high levels of fungicide SI resistance in populations of Venturia inaequalis, indicating that replacement programs are needed. This year she also confirmed resistance in the strobilurin (QoI) fungicides. Scab fungus (V. inaequalis) population monitoring plots involving several fungicide classes have been maintained in an area impacted by resistance to the SI fungicides. Since 2009 we have also observed a decline in SI control of powdery mildew in apple fungicide research plots compared to control achieved 17 years ago. Based on percent of treated and non-treated leaves infected, control declined from 70-90% in 1994 to less than 15% control in 2010. Several combination products or tank-mixes show promise for management of SI-resistant scab and other important early and late-season diseases. Luna Sensation (a package mix of fluopyram and trifloxystrobin) and Merivon (a mix of fluxopyroxad and pyraclstrobin) gave excellent control of powdery mildew and scab, as well as summer diseases; the combination of difenoconazole and cyprodinil (Inspire Super) contributed scab, rust and mildew control to early season alternating application schedules. Flutriafol (Topguard), a triazole fungicide, continued to give excellent powdery mildew and cedar-apple rust control. Pristine (pyraclostrobin + boscalid) gives excellent control of late season diseases. A new area of research in 2011 focused on integrated use of disease control products for crop load management through bloom thinning, an important aspect of organic production. Such relevant findings involving registered compounds provided revision input for the popular Spray Bulletin for Commercial Tree Fruit Growers which is annually utilized through more than 40,000 web hits and down-loads as well as the traditional printed copies. Experimental results were published in Plant Disease and on-line through Plant Disease Management Reports, and presented at national and regional scientific and commercial horticultural meetings. PARTICIPANTS: Individuals who worked on the project included research and extension scientists and state and privately sponsored technical staff and county agricultural agents. Clientele include county and regional agricultural agents and consultants and the end users who primarily include commercial and home fruit growers. There were approximately 40 opportunities for training among one or more of these groups. Meetings are organized to meet the joint needs of several related groups including training for extension agents at in-orchard meetings for growers, pest management scouts and agents regularly provide in-depth honing of disease, insect and horticultural problem diagnostic skills. TARGET AUDIENCES: The primary target audiences are commercial fruit growers and their advisors and home fruit growers. PROJECT MODIFICATIONS: During the past year there has been increased emphasis placed on web-based approaches, including regular posting of disease updates during the growing season on the blog at: http://treefruitdisease.blogspot.com/

Impacts
The potential for resistance by several important diseases to several fungicide classes, the need to manage ten or more diseases, and varying disease pressure from year to year across fruit-growing regions of Virginia underscore the need for ongoing testing of new materials and novel approaches for economical, environmentally sensitive tree fruit disease management. Ongoing fungicide and bactericide evaluations are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. Web-based presentation of research findings and in-orchard training represent useful forms of outcome assessment. New findings particularly relevant to the Virginia and mid-Atlantic fruit industry were presented at winter and in-orchard meetings with fruit growers. Tree fruit disease management information on a blog targeting the Winchester, VA area: http://treefruitdisease.blogspot.com/ was accessed 1,860 times from more than 50 different countries April-Dec.

Publications

  • Gleason M., J. Batzer, G. Sun, R. Zhang, M. Diaz Arias, T. Sutton, P. Crous, M. Ivanovic, P. McManus, D. Cooley, U. Mayr, R. Weber, K. Yoder, E. Del Ponte, A. Biggs, B. Oertel. 2011. A new view of sooty blotch and flyspeck. Plant Disease 95:368-383. http://apsjournals.apsnet.org/doi/pdfplus/10.1094/PDIS-08-10-0590
  • Marine, S. C., D. G. Schmale, K. S. Yoder. 2011. Seasonal distribution of SI fungicide resistance in apple scab populations in Virginia. Phytopathology 101:S114.
  • Jacon, G., T. Kippley, K. Cox, K. Yoder, G. Sundin, J. Alicandro, N. Halbrendt, H. Ngugi, T. Sutton. 2011. Tank-mixing of dodine in early-season apple scab programs and possibilities for renewed use in the eastern U.S. Phytopathology 101:S80.
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer, C. Cochran. 2011. Disease management with integrated fungicide programs on Red Delicious, Golden Delicious, and Rome apples, 2010. Plant Disease Management Reports 5:PF043.
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer, C. Cochran. 2011. Control of early season diseases by protectant fungicides on Nittany apple, 2010. Plant Disease Management Reports 5:PF042
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer, C. Cochran. 2011. Scab suppression by treatments first applied after lesions appeared on Ginger Gold, Jonagold, and Red Delicious apples, 2010. Plant Disease Management Reports 5:PF040.
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer, C. Cochran. 2011. Evaluation of experimental fungicides and mixed schedules on Stayman, Idared, and Granny Smith apples, 2010. Plant Disease Management Reports 5:PF041.
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer, C. Cochran. 2011. Control of powdery mildew and other diseases by experimental fungicides and integrated schedules on Idared apples, 2010. Plant Disease Management Reports 5:PF036.
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer. 2011. Control of bitter rot and Alternaria rot by postharvest dip treatments on Golden Delicious and Empire apples, 2010. Plant Disease Management Reports 5:PF039.
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer, C. Cochran. 2011. Disease control by experimental fungicides and mixtures on Golden Delicious, Idared, and York Imperial apples, 2010. Plant Disease Management Reports 5:PF035.
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer, C. Cochran, J. Saunders. 2011. Demonstration test of Topguard for mildew control under commercial conditions, 2010. Plant Disease Management Reports 5:PF038.
  • Yoder K., A. Cochran II, W. Royston, Jr., S. Kilmer. 2011. Scab and summer disease control by experimental and registered fungicides on Gala apple, 2010. Plant Disease Management Reports 5:PF037.


Progress 10/01/09 to 09/30/10

Outputs
OUTPUTS: Apple disease management research in 2010 focused on evaluation of 12 experimental materials for broad-spectrum fungal disease management and fungicide resistance management. These included 17 tests of 157 treatments on apples or peaches. Sterol-inhibiting (SI) fungicides have been valued in the past for after-infection control of scab, rusts and powdery mildew; however, the relative commercial value of these compounds is being compromised by development of resistance in the scab fungus in some areas of Virginia, especially in Frederick County. High levels of fungicide resistance in populations of Venturia inaequalis, identified by graduate student S. C. Marine in cooperation with Dr. D. G. Schmale, indicate that replacement programs are needed. Scab fungus (V. inaequalis) population monitoring plots involving several fungicide classes have been maintained in an area impacted by resistance to the SI fungicides. Since 2009 we have also observed a decline in SI control of powdery mildew in apple fungicide research plots compared to control achieved 15 years ago. Based on percent of treated and non-treated leaves infected, control declined from the 70-90 percent range in 1994 to less than 15 percent control in 2010. Several combination products or tank-mixes show promise for management of SI-resistant scab and other important early and late-season diseases. A package mix of fluopyram and trifloxystrobin (Luna Sensation, USF 2016A) gave excellent control of powdery mildew and scab, as well as summer diseases; the combination of difenoconazole and cyprodinil (A16001, Inspire Super) contributed scab, rust and mildew control to early season alternating application schedules. Flutriafol (Topguard), a triazole fungicide registered in 2010, gave excellent powdery mildew control in experimental and grower demonstration plots. Pristine (pyraclostrobin + boscalid) continues to give excellent control of late season diseases. Such relevant findings involving registered compounds provided revision input for the popular Spray Bulletin for Commercial Tree Fruit Growers which was utilized through more than 40,000 web hits and down-loads as well as the traditional printed copies. Experimental results were published in Plant Disease and on-line through Plant Health Progress and Plant Disease Management Reports, and presented at national and regional scientific and commercial horticultural meetings. PARTICIPANTS: Individuals who worked on the project included research and extension scientists and state and privately sponsored technical staff and county agricultural agents. Clientele include county and regional agricultural agents and consultants and the end users who primarily include commercial and home fruit growers. There were approximately 40 opportunities for training among one or more of these groups. Meetings are organized to meet the joint needs of several related groups including training for extension agents at in-orchard meetings for growers, pest management scouts and agents regularly provide in-depth honing of disease, insect and horticultural problem diagnostic skills. TARGET AUDIENCES: The primary target audiences are commercial and home fruit growers and their advisors. PROJECT MODIFICATIONS: During the past year there has been increased emphasis placed on web-based approaches, including initiation of the disease update blog: http://treefruitdisease.blogspot.com/

Impacts
The potential for resistance by several important diseases to several fungicide classes, the need to manage ten or more diseases, and varying disease pressure from year to year across fruit-growing regions of Virginia underscore the need for ongoing testing of new materials and novel approaches for economical, environmentally sensitive tree fruit disease management. Ongoing fungicide and bactericide evaluations are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. Web-based presentation of research findings and in-orchard training represent useful forms of outcome assessment. New findings particularly relevant to the Virginia and mid-Atlantic fruit industry were presented at winter and in-orchard meetings with fruit growers. Tree fruit disease management information on a blog targeting the Winchester, VA area: http://treefruitdisease.blogspot.com/ was accessed 2,965 times from 40 different countries April-Sept.

Publications

  • Biggs, A. R., D. R. Cooley, D. A. Rosenberger, and K. S. Yoder. 2010. Relative susceptibility of selected apple cultivars to sooty blotch and flyspeck. Online. Plant Health Progress doi:10.1094/PHP-2010-0726-01-RS.
  • Marine, S. C., K. S. Yoder, and A. Baudoin. 2010. Powdery mildew of apple. The Plant Health Instructor. DOI:10.1094/PHI-I-2010-1021-01.
  • Diaz Arias, M. M., J. C. Batzer, T. C. Harrington, A. W. Wong, S. C. Bost, D. R. Cooley, M. A. Ellis, J. R. Hartman, D. A. Rosenberger, G. W. Sundin, T. B. Sutton, J. W. Travis, M. J. Wheeler, K. S., Yoder, and M. L. Gleason. 2010. Diversity and biogeography of sooty blotch and flyspeck fungi on apple in the eastern and midwestern United States. Phytopathology 100:345-355. Online publication. doi/pdf/10.1094/PHYTO-100-4-0345.
  • Yoder, K. S, A. E. Cochran II, W. S. Royston, Jr. and S. K. Kilmer. 2010. Evaluation of experimental fungicides and mixed schedules on Stayman, Idared, and Ginger Gold apples, 2009. Plant Disease Management Reports 4:PF024. Online publication. doi: 10.1094/PDMR04.
  • Yoder, K. S, A. E. Cochran II, W. S. Royston, Jr. and S. K. Kilmer. 2010. Fire blight blossom blight suppression on Idared apple, 2009. Plant Disease Management Reports 4:PF023. Online publication. doi: 10.1094/PDMR04.
  • Yoder, K. S, A. E. Cochran II, W. S. Royston, Jr., S. K. Kilmer and C. Cochran. 2010. Disease management by experimental fungicides on Golden Delicious, Idared, and York Imperial apples, 2009. Plant Disease Management Reports 4:PF025. Online publication. doi: 10.1094/PDMR04.
  • Yoder, K. S, A. E. Cochran II, W. S. Royston, Jr. and S. K. Kilmer. 2010. Early season and summer disease control by experimental and registered fungicides on Nittany apple, 2009. Plant Disease Management Reports 4:PF022. Online publication. doi: 10.1094/PDMR04.
  • Yoder, K. S, A. E. Cochran II, W. S. Royston, Jr., S. K. Kilmer and C. Cochran. 2010. Early season disease management with combined fungicides on Red Delicious, Golden Delicious, and Rome apples, 2009. Plant Disease Management Reports 4:PF021. Online publication. doi: 10.1094/PDMR04.
  • Yoder, K. S, A. E. Cochran II, W. S. Royston, Jr., S. K. Kilmer and C. Cochran. 2010. Control of scab and brown rot by integrated fungicide programs on Loring peach, 2009. Plant Disease Management Reports 4:STF020. Online publication. doi: 10.1094/PDMR04.
  • Yoder, K., L. Combs, and R. Yuan. 2010. Effect of temperature on apple pollen tube growth: implications for bloom thinning. Proceedings of the 105th Annual Meeting of the Washington State Horticultural Association, pp. 68-78.
  • Biggs, A. R., G. W. Sundin, D. A. Rosenberger, K. S. Yoder, and T. B. Sutton, 2010. Relative susceptibility of selected apple cultivars to apple scab caused by Venturia inaequalis. Online. Plant Health Progress doi:10.1094/PHP-2010-0408-01-RS.


Progress 10/01/08 to 09/30/09

Outputs
OUTPUTS: Apple disease management research in 2009 focused on evaluation of 11 experimental materials for broad-spectrum fungal disease management, fungicide resistance management, and fire blight management. These included 18 tests of 159 treatments on apples or peaches. Sterol-inhibiting (SI) fungicides have been valued in the past for after-infection control of scab, rusts and powdery mildew; however, the relative commercial value of these compounds is being compromised by development of resistance in the scab fungus in some areas of Virginia, especially in Frederick county. High levels of fungicide resistance in populations of Venturia inaequalis, identified by graduate student S. C. Marine in cooperation with Dr. D. G. Schmale, indicate that replacement programs are needed. Scab fungus (V. inaequalis) population monitoring plots involving several fungicide classes have been maintained in an area impacted by resistance to the SI fungicides. In 2009 we noticed an additional concern: a decline in SI control of powdery mildew in apple fungicide research plots compared to control achieved 10-15 years ago. Several combination products or tank-mixes show promise for management of SI-resistant scab and other important early and late season diseases. A package mix of fluopyram and trifloxystrobin (USF 2016A, Luna Sensation) gave excellent control of powdery mildew and scab, as well as summer diseases; the combination of difenoconazole and cyprodinil (A16001, Inspire Super) contributed scab, rust and mildew control to early season alternating application schedules. Pristine (pyraclostrobin + boscalid) continues to give excellent control of late season diseases. Such relevant findings involving registered compounds provided revision input for the popular Spray Bulletin for Commercial Tree Fruit Growers which was utilized through more than 115,000 web hits and down-loads as well as the traditional printed copies. Experimental results were published in Plant Disease and on-line through Plant Health Progress and Plant Disease Management Reports, presented at national and regional scientific and commercial horticultural meetings. PARTICIPANTS: Individuals who worked on the project included research and extension scientists and state and privately sponsored technical staff and county agricultural agents. Clientele include county and regional agricultural agents and consultants and the end users who primarily include commercial and home fruit growers. There were approximately 40 opportunities for training among one or more of these groups. Meetings are organized to meet the joint needs of several related groups including training for extension agents at in-orchard meetings for growers, pest management scouts and agents regularly provide in-depth honing of disease, insect and horticultural problem diagnostic skills. TARGET AUDIENCES: The primary target audiences are commercial and home fruit growers and their advisors. PROJECT MODIFICATIONS: During the past year there has been increased emphasis placed on web-based approaches.

Impacts
The potential for resistance by several important diseases to several fungicide classes, the need to manage ten or more diseases, and varying disease pressure from year to year across fruit-growing regions of Virginia underscore the need for ongoing testing of new materials and novel approaches for economical, environmentally sensitive tree fruit disease management. Ongoing fungicide and bactericide evaluations are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. Web-based presentation of research findings and in-orchard training represent useful forms of outcome assessment. New findings particularly relevant to the Virginia and mid-Atlantic fruit industry were presented at winter and in-orchard meetings with fruit growers. Tree fruit disease management information on a web site targeting the Winchester, VA area was accessed 5,776 times during the survey period.

Publications

  • Biggs, A. R., Rosenberger, D. A., Yoder, K. S., Kiyomoto, R. K., Cooley, D. R., and Sutton, T. B. 2009. Relative susceptibility of selected apple cultivars to cedar apple rust and quince rust. Online. Plant Health Progress doi:10.1094/PHP-2009-1014-01-RS.
  • Biggs, A. R., Yoder, K. S., and Rosenberger, D. A. 2009. Relative susceptibility of selected apple cultivars to powdery mildew caused by Podosphaera leucotricha. Online. Plant Health Progress doi:10.1094/PHP-2009-1119-01-RS.
  • Sundin, G. W. N. A. Werner, K. S. Yoder, and H. S. Aldwinckle, 2009. Field Evaluation of Biological Control of Fire Blight in the Eastern United States.. Plant Dis. 93:386-394. doi:10.1094/PDIS-93-4-0386 http://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-93-4-0386
  • Yoder, K., R. Yuan, L. Combs, R. Byers, J. McFerson and T. Schmidt. 2009. Effects of temperature and the combination of liquid lime sulfur and fish oil on pollen germination, pollen tube growth, and fruit set in apples. HORTSCIENCE 44(5):1277-1283.
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. D. Douglas, and C. Cochran. 2009. Disease control by experimental fungicides on Golden Delicious, Idared, and York Imperial apples, 2008. Plant Disease Management Reports 3:PF004. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/PF0 04.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. D. Douglas, and C. Cochran. 2009. Experimental and mixed fungicide schedules on Stayman, Idared, and Granny Smith apples, 2008. Plant Disease Management Reports 3:PF002. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/PF0 02.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. D. Douglas, and C. Cochran. 2009. Postharvest bitter rot and white rot control by Scholar on Ginger Gold and Gala apples, 2008. Plant Disease Management Reports 3: PF019. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/PF0 19.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2009. Test of antibiotics and SAR candidates for blossom blight control on Golden Delicious and Rome Beauty apples, 2008. Plant Disease Management Reports 3: PF008. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/PF0 08.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2009. Suppression of fire blight by antibiotics on Idared apple, 2008. Plant Disease Management Reports 3: PF007. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/PF0 07.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. D. Douglas, and C. Cochran. 2009. Evaluation of apple scab "rescue" treatments applied to Gala and Fuji apples, 2008. Plant Disease Management Reports 3: PF006. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/PF0 06.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. D. Douglas, and C. Cochran. 2009. Disease management by fungicides first applied at petal fall on Idared apples, 2008. Plant Disease Management Reports 3:PF005. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/PF0 05.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. D. Douglas, and C. Cochran. 2009. Broad-spectrum disease management with alternating fungicide programs on three apple cultivars, 2009. Plant Disease Management Reports 3:PF003. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/PF0 03.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. D. Douglas, and C. Cochran. 2009. Scab and brown rot control by integrated fungicide programs on Redhaven peach and Redgold nectarine, 2008. Plant Disease Management Reports 3:STF023. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/STF 023.pdf
  • Yoder, K. S. A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. D. Douglas, and C. Cochran. 2009. Scab and brown rot control by Quash in integrated fungicide programs on peach and nectarine, 2008. Plant Disease Management Reports 3:STF024. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2009/STF 024.pdf


Progress 10/01/07 to 09/30/08

Outputs
OUTPUTS: Apple disease management research in 2008 focused on evaluation of 12 experimental materials for "soft" or biological control, broad-spectrum fungal disease management, and fungicide resistance management, and fire blight management. These included 17 tests of 144 treatments. Sterol-inhibiting (SI) fungicides have been valued in the past for after-infection control of scab, rusts and powdery mildew; however, the relative commercial value of these compounds is being compromised by development of resistance in the scab fungus in some areas of Virginia. High levels of fungicide resistance in populations of Venturia inaequalis, identified by graduate student S. C. Marine in cooperation with Dr. D. G. Schmale, indicate that replacement programs should be considered. Scab fungus (V. inaequalis) population monitoring plots involving several fungicide classes were established in an area impacted by resistance to the SI fungicides. Several combination products or tank-mixes show promise for management of SI-resistant scab and other important early and late season diseases. Unusual weather conditions in 2008 brought losses of as much as 40% fruit infection by rust diseases to some orchards which could have been averted by use of the SI fungicides, but their non-use was due to resistance concerns in scab. Such relevant findings involving registered compounds provided revision input for the popular Spray Bulletin for Commercial Tree Fruit Growers which was utilized through 114,000 web hits and down-loads as well as the traditional printed copies. Experimental results were published on-line through Postharvest Biology and Technology and Plant Disease Management Reports, presented at national and regional scientific and commercial horticultural meetings. PARTICIPANTS: Individuals who worked on the project included research and extension scientists and state and privately sponsored technical staff and county agricultural agents. Clientele include county and regional agricultural agents and consultants and the end users who primarily include commercial and home fruit growers. There were approximately 40 opportunities for training among one or more of these groups and frequently meetings are organized to meet the joint needs of several related groups including training for extension agents at in-orchard meetings for growers, pest management scouts and agents regularly provide in-depth honing of disease, insect and horticultural problem diagnostic skills. TARGET AUDIENCES: The primary target audiences are commercial and home fruit growers and their advisors. PROJECT MODIFICATIONS: During the past year there has been increasing emphasis placed on web-based approaches.

Impacts
The potential for resistance by several important diseases to several fungicide classes, the need to manage ten or more diseases, and varying disease pressure from year to year across fruit-growing regions of Virginia underscore the need for ongoing testing of new materials and novel approaches for economical, environmentally sensitive tree fruit disease management. Ongoing fungicide and bactericide evaluations are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. Web-based presentation of research findings and in-orchard training represent useful forms of outcome assessment. New findings particularly relevant to the Virginia and mid-Atlantic fruit industry were presented at winter and in-orchard meetings with fruit growers. Tree fruit disease management information on a web site targeting the Winchester, VA area was accessed 6,104 times during the survey period, a 15% increase over same period in 2007.

Publications

  • Janisiewicz, W.J, R.A Saftner, W.S. Conway, K.S. Yoder. 2008. Control of blue mold decay of apple during commercial controlled atmosphere storage with yeast antagonists and sodium bicarbonate. Postharvest Biology and Technology 49:374-378. http://ddr.nal.usda.gov/dspace/bitstream/10113/18511/1/IND44070292.pd f
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer. 2008. Concentrate applications of experimental fungicides on Golden Delicious apple, 2007. Plant Disease Management Reports 2:PF033. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 33.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. Cochran. 2008. Performance of an experimental fungicide and mixtures on Stayman, Idared, and Ginger Gold apples, 2007. Plant Disease Management Reports 2:PF034. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 34.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer, C. Cochran. 2008. Evaluation of experimental fungicides on Golden Delicious, Idared, and York Imperial apples, 2007. Plant Disease Management Reports 2:PF045. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 45.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2008. Summer disease management with experimental fungicides on Idared apples, 2007. Plant Disease Management Reports 2:PF035. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 35.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer. 2008. Summer disease and post-storage rot control by experimental fungicides on Idared apples, 2006-07. Plant Disease Management Reports 2:PF036. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 36.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer. 2008. Test of Agri-Fos and ProPhyt for disease management on Red Delicious, Golden Delicious, and Rome apples, 2007. Plant Disease Management Reports 2:PF025. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 25.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer. 2008. Evaluation of a biological material and Agri-Fos trunk treatments for early season disease control on Gala apple, 2007. Plant Disease Management Reports 2:PF024. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 24.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer. 2008. Test of Agri-Fos /Pentra-Bark trunk treatments for early season disease control on Jonagold apple, 2007. Plant Disease Management Reports 2:PF023. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 23.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer. 2008. Test of Agri-Fos/ Pentra-Bark trunk treatments and foliar antibiotic applications for blossom blight control, 2007. Plant Disease Management Reports 2:PF022. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 22.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer. 2008. Fire blight control by experimental antibiotics on Idared apple blossoms, 2007. Plant Disease Management Reports 2:PF021. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/PF0 21.pdf
  • Yoder, K.S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer. 2008. Disease management by experimental fungicides on Loring peach and Redgold nectarine, 2007. Plant Disease Management Reports 2:STF014. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2008/STF 014.pdf


Progress 10/01/06 to 09/30/07

Outputs
OUTPUTS: Apple disease management research in 2007 focused on evaluation of 16 experimental materials for "soft" or biological control, broad-spectrum fungal disease management, and fungicide resistance management, and fire blight management. These included 16 tests of 144 treatments. Sterol-inhibiting (SI) fungicides have been valued in the past for after-infection control of scab, rusts and powdery mildew; however, the relative commercial value of these compounds is being compromised by development of resistance in the scab fungus in some areas of Virginia. High levels of fungicide resistance in populations of V. inaequalis, identified by graduate student S. C. Marine in cooperation with Dr. D. G. Schmale, indicate that replacement programs should be considered. Scab fungus (Venturia inaequalis) population monitoring plots involving several fungicide classes were established in an area impacted by resistance to the SI fungicides. Several combination products or tank-mixes show promise for management of SI-resistant scab and other important early and late season diseases. Such relevant findings involving registered compounds provided revision input for the popular Spray Bulletin for Commercial Tree Fruit Growers which was utilized through 115,000 web hits and down-loads as well as the traditional printed copies. Experimental results were published on-line through Plant Health Progress and Plant Disease Management Reports, presented at national and regional scientific and commercial horticultural meetings. PARTICIPANTS: Individuals who worked on the project included research and extension scientists and state and privately sponsored technical staff and county agricultural agents. Clientele include county and regional agricultural agents and consultants and the end users who primarily include commercial and home fruit growers. There were approximately 40 opportunities for training among one or more of these groups and frequently meetings are organized to meet the joint needs of several related groups. The in-service training for extension agents and in-orchard meetings for growers, pest management scouts and agents regularly provide in-depth honing of disease, insect and horticultural problem diagnostic skills. TARGET AUDIENCES: The primary target audiences are commercial and home fruit growers and their advisors. PROJECT MODIFICATIONS: During the past year more emphasis has been placed on "training the trainer" and web-based approaches.

Impacts
The potential for resistance by several important diseases to several fungicide classes, the need for control of ten or more diseases, and varying disease pressure from year to year across fruit-growing regions of Virginia underscore the need for ongoing testing of new materials and novel approaches for economical, environmentally sensitive tree fruit disease management. Ongoing fungicide evaluations are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. Web-based presentation of research findings and in-service training represent useful forms of outcome assessment: New findings particularly relevant to the Virginia and mid-Atlantic fruit industry were presented at In-service Fruit Training (Oct. 2007) during which VA extension agent attendees increased their knowledge fruit culture and pest management four-fold, and at winter and in-orchard meetings with fruit growers. Tree fruit disease management information on a web site targeting the Winchester, VA area was accessed 5,306 times during the survey period and increased 176% over web visits during June-September compared to the same period in 2006.

Publications

  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2007. Effect of late-season and postharvest fungicide treatments on storage decay in two apple cultivars, 2005-06. Plant Disease Management Reports 1:PF027. URL: http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 27.pdf
  • Marine, S.C., D.G Schmale III, and K.S. Yoder. 2007. Resistance to myclobutanil in populations of Venturia inaequalis in Winchester, Virginia. Plant Health Progress DOI:10.1094/PHP-2007-1113-01-RS. http://www.plantmanagementnetwork.org/sub/php/research/2007/applescab /
  • Yoder, K. S., A. E. Cochran II, S. W. Kilmer, W. S. Royston, Jr., and S. Cochran. 2007. Broad-spectrum disease management by alternate fungicide programs on three apple cultivars, 2006. Plant Disease Management Reports 1: PF030. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 30.pdf
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2007. Integrated biological and streptomycin treatments for fire blight control on Idared apples, 2006. Plant Disease Management Reports 1:PF028. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 28.pdf
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer and S. Cochran. 2007. Full season disease management by experimental fungicides on Gala apple, 2006. Plant Disease Management Reports 1:PF032. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 32.pdf
  • Yoder, K. S., A. E. Cochran II, S. W. Kilmer and W. S. Royston, Jr. 2007. Postharvest rot control by Scholar formulations on Fuji apples, 2005-06. Plant Disease Management Reports 1: PF026. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 26.pdf
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer and L. Brumback. 2007. Season-long disease management by experimental fungicides on Golden Delicious, Idared, and York apples, 2006. Plant Disease Management Reports 1:PF034. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 34.pdf
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer and L. Brumback. 2007. Disease control by experimental fungicides on Golden Delicious and Rome Beauty apples, 2006. Plant Disease Management Reports 1:PF033. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 33.pdf
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer and S. Cochran. 2007. Disease control by flutriafol and mixed schedules on Stayman, Idared, and Granny Smith apples, 2006. Plant Disease Management Reports 1: PF031. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 31.pdf
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer and L. Brumback. 2007. Evaluation of experimental fungicides for fire blight and fungal disease management on Nittany apple, 2006. Plant Disease Management Reports 1:PF029. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 29.pdf
  • Yoder, K. S., A. E. Cochran II, S. W. Kilmer and W. S. Royston, Jr. 2007. Evaluation of gentamicin for fire blight control on Golden Delicious apple, 2006. Plant Disease Management Reports 1:PF035. http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2007/PF0 35.pdf


Progress 10/01/05 to 09/30/06

Outputs
Apple disease management research in 2006 focused on evaluation of 12 experimental compounds for broad-spectrum fungal disease control and fungicide resistance management, and included 14 tests of 127 treatments. Sterol-inhibiting (SI) fungicides have been valued in the past for after-infection control of scab, rusts and powdery mildew; however, the relative commercial value of these compounds is being compromised by development of resistance in the scab fungus in some areas of Virginia. Scab fungus (Venturia inaequalis) population monitoring plots involving several fungicide classes were established in an area where resistance to the SI fungicides was first found in 2004. Testing of 73 scab isolates on agar that contained the SI fungicide, myclobutanil, was conducted by graduate student S. C. Marine in cooperation with Dr. D. G. Schmale III. Growth of isolates from SI-treated trees was significantly less inhibited than those collected from non-treated trees. High levels of fungicide resistance in populations of Venturia inaequalis indicate that replacement programs should be considered. Under moderate scab pressure, the strobilurin compound trifloxystrobin (Flint) performed better than myclobutanil (Nova) for scab control. Several combination products or tank-mixes show promise for management of SI-resistant scab and other important early and late season diseases. Pristine, a mixture of pyraclostrobin and boscalid from two chemical classes, also gave excellent control of scab and flyspeck and good control of sooty blotch mildew and several fruit rots. Six experimental SI fungicides gave expected control of cedar-apple and quince rusts and powdery mildew. But the experimental sterol-inhibiting fungicides, difenoconazole and fenbuconazole, were also surprisingly effective for control of sooty blotch and fly speck. Tanos (a mixture of famoxadone and cymoxanil) was comparable to captan for control of sooty blotch, flyspeck and rots. Two repeated developments confirm potential for improved control of postharvest rot problems: Pristine, applied in the orchard in the late cover sprays, improved postharvest control of bitter, Botryosphaeria, and Alternaria rots as well as Penicillium blue mold. Fludioxonil (Scholar) applied as a postharvest dip treatment, suppressed latent bitter rot and controlled blue mold. Testing of selected materials for managing fire blight on apple involved three tests of 30 treatments which included four biocontrol agents, two antibiotics, copper materials and other fungicides. A tank-mix of two antibiotics, streptomycin and gentamicin gave improved control. In a year in which fire blight control was quite variable among biological control products, Serenade (Bacillus subtilis), did give significant control.

Impacts
The potential for resistance by several important diseases to several fungicide classes, the need for control of ten or more diseases, and varying disease pressure from year to year across fruit-growing regions of Virginia underscore the need for ongoing testing of new materials and novel approaches for economical, environmentally sensitive tree fruit disease management. Ongoing fungicide evaluations are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. A long-term goal of the resistance monitoring research is to direct it toward DNA-based methodologies so that we can rapidly screen for fungicide resistance and more quickly employ the appropriate disease management strategies.

Publications

  • Brown, M. W., S. S. Miller, and K. S. Yoder 2005. Stink bug (Pentatomidae) feeding preferences among apple cultivars. J. Am. Pomological Soc. 60(3):144-148.
  • Yoder, K., A. Cochran II, W. Royston, Jr., S. Kilmer and L. Brumback. 2006. Fireblight control by integrated biological and streptomycin treatments on Idared apple, 2005. Biological and Cultural Tests for Control of Plant Diseases B&C Tests 21:N004
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2006. Storage rot control by postharvest dip treatments on Fuji and Golden Delicious apples, 2004-05. F&N Tests 61:PF013.
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2006. Blossom blight control by antibiotics on Idared apple, 2005. F&N Tests 61:PF014.
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2006. Control of fireblight and fungal diseases by experimental and registered fungicides on Nittany apple, 2005. F&N Tests 61:PF015.
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2006. Fungal disease control by organic and biocontrols on Jonagold apple, 2005. F&N Tests 61:PF016.
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., S. W. Kilmer and L. Brumback. 2006. Evaluation of mixed fungicide schedules on Stayman, Idared, and Ginger Gold apples, 2005. F&N Tests 61:PF017.
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2006. Evaluation of experimental and recently registered fungicides on Golden Delicious apple, 2005. F&N Tests 61:PF018.
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2006. Broad-spectrum disease management by certified organic and home fruit fungicides on three apple cultivars, 2005. F&N Tests 61:PF019.
  • Yoder, K. S., A. E. Cochran II, W. S. Royston, Jr., and S. W. Kilmer. 2006. Broad-spectrum disease control on Loring peach and Redgold nectarine, 2005. F&N Tests 61:STF009.