Progress 08/01/05 to 07/31/09
Outputs
OUTPUTS: Conducted 8 blueberry field trials Conducted 15 laboratory trials Monitored 4 blueberry fields weekly for diseases annually Made presentations at 20 grower meetings, workshops, and conferences. Prepared numerous extension articles related to this project. Developed a disease prediction model for anthracnose fruit rot in blueberry, which will be available in 2010. Updated and expanded information on the MSU blueberry website (www.blueberries.msu.edu) Prepared two new fact sheets. Updated the blueberry pocket IPM Scouting guide (which was also translated into Spanish) PARTICIPANTS: The main participants in this project were Jerri Gillett (Research Assistant), Roger Sysak (Research Technician), and Timothy Miles (PhD student) who conducted the field and laboratory research activities with assistance from undergraduate students. We also worked closely with Rufus Isaacs (Assoc. Professor Dept. Entomology), Keith Mason (Research Assistant, Dept. Entomology) and Paul Jenkins (MSU IPM Program Small Fruit Educator) as part of a project demonstrating the benefits of scouting for diseases and insects. Jeffrey Andresen and Tracy Aichele (Department of Geography) helped develop the disease prediction model and were in charge of the Michigan Automated Weather Network which provided weather data for this project. Experiments were conducted in fields of blueberry growers and at the Trevor Nichols Research Complex in Fennville, Michigan in collaboration with John Wise (Research manager, Dept. Entomology). Research was also done at the Southwest Michigan Research and Extension Center in collaboration with Dave Francis (farm manager) and Tom Zabadal (station director). The project provided training opportunities for Timothy Miles (PhD student) in doing field research and extension, as well as research training for six undergraduate students. Information gathered in this project is shared with on average 25-30 participants in the MSU Blueberry IPM Scout Training Certificate Program, which is held annually. Grower meetings had as many as 70 attendees. Partner organizations are the Michigan Blueberry Growers Association and Michigan Blueberry Advisory Council. TARGET AUDIENCES: The primary target audience for the project is blueberry growers in Michigan and other Great Lakes states as well as extension personnel and private consultants. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The environmental infection requirements and appressorium formation of C. acutatum were investigated in Jersey fruit in nine replicated experiments with potted plants with green fruit, detached twigs with both green and blue fruit, and detached blue fruit. In general, the minimum wetness duration required for infection was 8 to 12 hr at 20 and 25 C, 18 hr at 15 C, and 36 hr at 10 C. The optimal temperature for infection in this study was 25 C. An anthracnose fruit rot risk chart was developed based on the combined data and was evaluated in three separate field trials. A systemic fungicide applied after wetness periods of 6 and 12 hours worked as well as calendar-based sprays and saved 1 to 2 sprays per season. Spray programs using longer wetness durations action thresholds were not as effective. A disease prediction model was developed and incorporated in the MSU Enviro-Weather website. Conidia were collected in rain traps in three blueberry plantings in 2005, 2006, 2007, and 2008 to determine seasonal patterns in spore production. Peaks in conidium dispersal occurred during bloom and early fruit development and again during harvest. The first peak usually occurred when a cumulative total of 132-140 mm rainfall had been reached since April 1 of that year. Rainfall was better correlated with conidium dispersal than temperature. Anthracnose fruit rot infection increased dramatically during harvest. In order to demonstrate the benefits of scouting for management of mummy berry, four field sites in SW Michigan were monitored from 2007 to 2009. Disease pressure was higher in 2008 and 2009 than in 2007. The number of overwintered pseudosclerotia, pseudosclerotia with apothecia, number of apothecia, size of apothecial cups, number of blighted shoots, and the number of mummified berries were counted weekly from April through August each year. The number of apothecia overall had the strongest correlation with the amount of disease at the end of the growing season. Inoculation experiments with Monilinia vaccinii-corymbosi at different freezing temperatures (-0.5, -1.0, -1.5, and -2.0 C) showed that freezing predisposed young shoots to infection. In five field trials, frost-guided fungicide sprays (fenbuconazole within 24 hours of a frost) improved disease control over calendar-based sprays; however, differences were not always significant, and in some years, few or no frosts occurred. The project has lead to improved recommendations and control of mummy berry and anthracnose in blueberry fields in Michigan. One grower reported a savings of $100,000 in fungicides. Updated recommendations and new information were made available to blueberry growers in Michigan and other states through weekly electronic IPM updates, extension articles, the Blueberry IPM Scout Training Course, bi-weekly field meetings, the Michigan Fruit Management Guide, and new fact sheets (mummy berry, anthracnose). In addition, the information gathered in this project was used for a second edition of the Pocket Guide to IPM Scouting in Highbush Blueberries, which has been translated in Spanish as well. An IPM Guide for blueberries will be published in 2010.
Publications
- Wise, J. C., Gut, L. J., Isaacs, R., Schilder, A. M. C., Sundin, G. W., Zandstra, B., Hanson, E., and Shane, B. 2009. Michigan Fruit Management Guide 2010. Extension Bulletin E-154. Michigan State University, East Lansing, MI.
- Miles. T. D., and Schilder, A. C. 2009. Correlation of signs and symptoms of mummy berry in highbush blueberry Acta Horticulturae 810: 379-384.
- Schilder, A. 2009. Overview of blueberry diseases during the 2009 season. Fruit Crop Advisory Team Alert Newsletter (http://ipmnews.msu.edu/fruit/). Posted September 22, 2009.
- Wise, J., Zandstra, B., Miyazaki, S., and Schilder, A. 2009. Speciality (minor-use) crop pesticide prioritization in the 2009 Ir-4 Food Use Workshop. Fruit Crop Advisory Team Alert Newsletter (http://ipmnews.msu.edu/fruit/). Posted September 22, 2009.
- Schilder, A., and Miles. T. 2009. If blueberries are still in bloom, keep up mummy berry sprays Fruit Crop Advisory Team Alert Newsletter (http://ipmnews.msu.edu/fruit/). Posted June 2, 2009.
- Schilder, A. 2009. Bloom and early fruit development: A good time to control fruit rots in blueberries. Fruit Crop Advisory Team Alert Newsletter (http://ipmnews.msu.edu/fruit/). Posted June 2, 2009.
- Schilder, A. 2009. Omega 500 F fungicide labeled for blueberries. Fruit Crop Advisory Team Alert Newsletter (http://ipmnews.msu.edu/fruit/). Posted May 12, 2009.
- Schilder, A., and Miles, T. 2009. Time to scout for mummy berry in blueberry fields. Fruit Crop Advisory Team Alert Newsletter (http://ipmnews.msu.edu/fruit/). Posted April 28, 2009.
- Schilder, A. 2009. 2009 Fungicide update for blueberry. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (1): 5-6.
- Schilder, A., and Miles, T. 2009. Disease management: mummy berry. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (2): 5-6.
- Schilder, A., and Miles, T. 2009. Blueberry disease scouting protocols. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (2): 9.
- Schilder, A., and Miles, T. 2009. Disease management: Mummy berry: apothecia are everywhere. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (3): 4-6.
- Schilder, A., and Miles, T. 2009. Disease management: Mummy berry. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (4): 3-4.
- Schilder, A., and Miles, T. 2009. Disease management: Mummy berry: shoot strikes. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (5): 4-5.
- Schilder, A., and Miles, T. 2009. Disease management: Mummy berry. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (6): 4-5.
- Schilder, A., and Miles, T. 2009. Disease management: mummy berry: shoot and flower strikes. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (7): 5-6.
- Schilder, A., and Miles, T. 2009. Disease management: mummy berry and blueberry shoestring virus. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (8): 3-5.
- Schilder, A. 2009. If blueberries are still in bloom, keep up mummy berry sprays. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (8): 5.
- Schilder, A. 2009. Bloom and early fruit development: a good time to control fruit rots in blueberries. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (8): 6-7.
- Schilder, A., and Miles, T. 2009. Disease management: mummy berry and twig blights. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (9): 5-6.
- Schilder, A. 2009. Blossom and twig blight in blueberry. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (9): 8.
- Schilder, A. and Miles, T. 2009. Disease management: twig blight and mummy berry. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (10): 4-5.
- Schilder, A. and Miles, T. 2009. Disease management: blossom blights and mummy berry fruit infection. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (11): 6-7.
- Schilder, A. and Miles, T. 2009. Disease management: mummy berry and mosaic. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (12): 3-4.
- Schilder, A. and Miles, T. 2009. Disease management: blighted twigs and mummy berry. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (13): 3-5.
- Schilder, A. and Miles, T. 2009. Disease management: mummy berry. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (14): 6-8.
- Schilder, A. and Miles, T. 2009. Disease management: fruit rots. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (15): 5-6.
- Schilder, A. and Miles, T. 2009. Disease management: anthracnose and Alternaria fruit rot. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (16): 3-4.
- Schilder, A. and Miles, T. 2009. Disease management. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (17): 5-6.
- Schilder, A. and Miles, T. 2009. Disease management. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (18): 4-5.
- Schilder, A. and Miles, T. 2009. Disease management: anthracnose infections throughout this season. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (19): 4-5.
- Schilder, A. and Miles, T. 2009. Disease management: season overview. Blueberry IPM Newsletter (http://www.isaacslab.ent.msu.edu/blueberryscoutarchive.htm) 3 (20): 3-5.
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Progress 08/01/07 to 07/31/08
Outputs
OUTPUTS: The environmental infection requirements of C. acutatum continued to be investigated in Jersey fruit in replicated experiments with potted plants with green fruit, detached twigs with both green and blue fruit, and detached blue fruit. Green and/or blue fruit were inoculated with a conidial suspension and incubated at 10, 15, 20, 25, or 30 degrees C and 3, 6, 12, 18, 24, 36, or 48 hours of wetness. Fruit were evaluated for the presence of C. acutatum after 7-12 days of incubation. In general, the minimum wetness duration required for infection was 12 hr at 20 and 25 C, 18 hr at 15 C, and 36 hr at 10 C. The optimal temperature for infection was 25 C. In a field trial conducted using wetness period as a disease predictor, two Cabrio (pyraclostrobin) sprays applied after wetness periods of 12 h were as effective as 8 weekly (calendar-based sprays). In addition, conidia were collected in rain traps in three different blueberry plantings in SW Michigan from April until August to determine peaks in spore production. Peaks in conidium dispersal occurred later (June-July) in 2008 than in previous years, likely due to the cold spring and early summer. In order to demonstrate the benefits of scouting for management of mummy berry, signs and symptoms were quantified again in 2008 in four field sites in SW Michigan (cultivars Rubel, Jersey, and Blueray). Disease pressure was higher in 2008 than 2007. The number of overwintered pseudosclerotia, pseudosclerotia with apothecia, number of apothecia, number of blighted shoots, and the number of infected berries were counted weekly from April through August, 2008. Apothecia were observed from April 11 until May 15, 2008; the maximum pseudosclerotium germination rate was 31%; blighted shoots were observed from May 9 to July 1; and infected berries were first observed on July 6. Mummified berries were counted in the bush and on the ground before harvest. Regression analyses were performed to determine which variable would best predict the number of primary and secondary infections. In both years, the number of apothecia overall had the strongest correlation with the amount of disease at the end of the growing season. Videotaped observations of shoot strikes in the field showed that flies may play a greater role than bees in conidium transmission to flowers. Additional inoculation experiments with Monilinia vaccinii-corymbosi at different freezing temperatures (-0.5, -1.0, -1.5, and -2.0 degrees C) showed that freezing predisposed the young shoots to infection, although in the case of Sierra, freezing was not needed for infection when the inoculum concentration was high. Refrigerated spores were better than frozen spores. Temperatures < -1.5 C were injurious to the leaves in some cases. In a field trial in Jersey blueberries, frost-guided fungicide sprays (fenbuconazole within 24 hours of a frost) were numerically but not statistically better than calendar-based sprays, however, there was only one frost event. PARTICIPANTS: The main participants in this project were Jerri Gillett (Research Assistant), Roger Sysak (Research Technician), and Timothy Miles (PhD student) who conducted the field and laboratory research activities with assistance from undergraduate students. We also worked closely with Rufus Isaacs (Assoc. Professor Dept. Entomology), Keith Mason (Research Assistant, Dept. Entomology) and Paul Jenkins (MSU IPM Program Small Fruit Educator) as part of a project demonstrating the benefits of scouting for diseases and insects. Experiments were conducted in fields of various Michigan blueberry growers and of the Trevor Nichols Research Complex in Fennville, Michigan in collaboration with John Wise (Research manager, Dept. Entomology). The project provided training opportunities for Timothy Miles (PhD student) in doing field research and extension, as well as research training for various undergraduate students. Information gathered in this project is shared with on average 25-30 participants in the MSU Blueberry IPM Scout Training Certificate Program, which is held annually. Partner organizations are the Michigan Blueberry Growers Association and Michigan Blueberry Advisory Committee. TARGET AUDIENCES: The primary target audience for the project is blueberry growers in Michigan and other states as well as extension personnel and private consultants. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The project so far has lead to improved recommendations and control of mummy berry and anthracnose in blueberry fields in Michigan. Updated recommendations and new information were made available to blueberry growers in Michigan and other states through weekly electronic IPM updates, extension (CAT Alert) articles, the Blueberry IPM Scout Training Course, bi-weekly field meetings, the Michigan Fruit Management Guide, and several new fact sheets (Mummy berry, anthracnose). In addition, the information gathered in this project was used for a second edition of the Pocket Guide to IPM Scouting in Highbush Blueberries, which has been translated in Spanish as well. Furthermore, some of the new findings were included in a revision of the APS Compendium of Blueberry, Cranberry, and Lingonberry diseases and insects, which will be published in 2009.
Publications
- Miles. T. D., and Schilder, A. M. C. 2008. Correlation of mummy berry signs and symptoms. Acta Horticulturae (in press).
- Gillett, J. M., and Schilder, A. M. C. 2008. Environmental requirements for infection of blueberry fruit by Colletotrichum acutatum. Acta Horticulturae (in press).
- Schilder, A., Isaacs, R., Hanson, and Cline, B. 2008. A Pocket Guide to IPM Scouting in Highbush Blueberries. Michigan State University Extension Bulletin E-2928. 2nd Edition.
- Schilder, A., Isaacs, R., Hanson, Cline, B., Garcia-Salazar, C., and France, A. 2008. A Pocket Guide to IPM Scouting in Highbush Blueberries. Michigan State University Extension Bulletin E-2928. (Spanish version).
- Wise, J. C., Gut, L. J., Isaacs, R., Schilder, A. M. C., Sundin, G. W., Zandstra, B., Hanson, E., and Shane, B. 2008. Michigan Fruit Management Guide 2009. Extension Bulletin E-154. Michigan State University, East Lansing, MI.
- Miles, T., and Schilder, A. 2008. Disease update: mummy berry. Michigan Blueberry IPM Update, Vol. 2 (1): 3.
- Schilder, A. 2008. Pest of the week: mummy berry. Michigan Blueberry IPM Update, Vol. 2 (1): 5-6.
- Schilder, A. 2008. Fungicide label update. Michigan Blueberry IPM Update, Vol. 2 (1): 8-9.
- Miles, T., and Schilder, A. 2008. Disease update: Attack of the mummy berries! Michigan Blueberry IPM Update, Vol. 2 (2): 3.
- Miles, T., and Schilder, A. 2008. Disease update: Mummy berry. Michigan Blueberry IPM Update, Vol. 2 (3): 4.
- Schilder, A. 2008. Pest of the Week: Botrytis. Michigan Blueberry IPM Update, Vol. 2 (3): 2.
- Schilder, A. 2008. Topsin M Section 18 request for blueberries still pending. Michigan Blueberry IPM Update, Vol. 2 (3): 9.
- Miles, T., and Schilder, A. 2008. Disease update: Mummy berry presses on. Michigan Blueberry IPM Update, Vol. 2 (4): 4.
- Miles, T., and Schilder, A. 2008. Pest of the week, anthracnose. Michigan Blueberry IPM Update, Vol. 2 (5): 2.
- Miles, T., and Schilder, A. 2008. Disease update: Shoot strikes strike back! Michigan Blueberry IPM Update, Vol. 2 (5): 4.
- Schilder, A. 2008. Topsin M Section 18 request for blueberries denied by EPA. Michigan Blueberry IPM Update, Vol. 2 (4): 5.
- Schilder, A. 2008. PropiMax fungicide labeled for use in blueberries. Fruit Crop Advisory Team Vol. 23 (2).
- Schilder, A. 2008. Now is a good time to monitor for mummy berry in blueberries. Fruit Crop Advisory Team Vol. 23 (3).
- Jenkins, P., Isaacs, R., and Schilder, A. 2008. Blueberry IPM kick-off meeting. Fruit Crop Advisory Team Vol. 23 (3). Schilder, A. 2008. Topsin M Section 18 request for blueberries still pending. Fruit Crop Advisory Team Vol. 23 (5).
- Miles, T., and Schilder, A. 2008. Mummy berry shoot strikes sighted in blueberries. Fruit Crop Advisory Team Vol. 23 (6).
- Schilder, A. 2008. Topsin M Section 18 request for blueberries denied by EPA. Fruit Crop Advisory Team Vol. 23 (7).
- Schilder, A., Wharton, P., and Miles. T. 2008. Mummy berry. Michigan State University Extension Bulletin E-2846.
- Miles. T., and Schilder, A. 2008. Anthracnose Fruit Rot. Michigan State University Extension Bulletin, E-3039.
- Miles, T. D., Wharton, P. S., and Schilder, A. M. C. 2008. Cytological and chemical evidence for an active resistance response to infection by Colletotrichum acutatum in Elliott blueberries. Acta Horticulturae (in press).
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Progress 08/01/06 to 07/31/07
Outputs
The environmental infection requirements of C. acutatum were investigated in Jersey fruit in four different replicated experiments with potted plants with green fruit, detached twigs with both green and blue fruit, and detached blue fruit. Green and/or blue fruit were inoculated with a conidial suspension and incubated at 10, 15, 20, 25, or 30 degrees C and 3, 6, 12, 18, 24, 36, or 48 hours of wetness. At the end of the incubation period, fruit on potted plants were dried with forced air and allowed to ripen naturally. Green and blue fruit on detached twigs as well as detached blue fruit were removed and surface sterilized with 10% bleach for 2 min. Green fruit was cut in half and placed on potato dextrose agar in Petri dishes, and blue fruit was incubated in moist chambers at room temperature and 100% relative humidity. Fruit were evaluated for the presence of C. acutatum after 7-12 days of incubation. Background infection was found to be a problem in some of the
fruit lots. In general, the minimum wetness duration required for infection was 12 hr at 20 and 25 C, 18 hr at 15 C, and 36 hr at 10 C. The optimal temperature for infection was 25 C. In addition, conidia were collected in rain traps in three different blueberry plantings in SW Michigan from April until September to determine peaks in spore production. Data will be subjected to regression analysis to determine what environmental variables are best correlated with spore dispersal. In order to demonstrate the benefits of scouting for management of mummy berry, signs and symptoms were quantified. Four field sites in southwest Michigan (cultivars Rubel, Jersey, and Blueray) were evaluated weekly from April through August 2007. The number of overwintered pseudosclerotia, pseudosclerotia with apothecia, number of apothecia, number of blighted shoots, and the number of infected berries were counted at ten locations per field. At the beginning of the season, one field had low, two fields had
intermediate and one field had high numbers of pseudosclerotia. Apothecia were observed from April 16 until May 11; blighted shoots were observed from May 11 to June 8; and infected berries were first observed on June 22. Mummified berries were counted in the bush and on the ground on July 6, right before harvest. Regression analyses were performed to determine which variable would best predict the number of primary and secondary infections. At all four sites the number of apothecia had the strongest correlation with the amount of overall disease at the end of the growing season. Two inoculation experiments with Monilinia vaccinii-corymbosi at different freezing temperatures (-0.5, -1.0, -1.5, and -2.0 degrees C) showed that freezing predisposed the young shoots to infection. However, infection levels were low and temperatures < -1.5 C were injurious to the leaves. In a field trial in Jersey blueberries, frost-guided vs. calendar-based fungicide (fenbuconazole) sprays did not show a
significant difference; however, there were few frost events.
Impacts
Lime sulfur sprays applied to the bush at early green tip or to the ground significantly reduced mummy berry shoot strikes but not mummified fruit at harvest.
Publications
- Schilder, A. 2007. Monitor for mummy berry in blueberries. Fruit Crop Advisory Team Vol. 22: 5.
- Schilder, A. 2007. Mummy berry update in blueberries. Fruit Crop Advisory Team Vol. 22: 6.
- Schilder, A. 2007. Blossom blight in blueberries. Fruit Crop Advisory Team Vol. 22: 7.
- Schilder, A. 2007. Overview of small fruit diseases during the 2007 growing season. Fruit Crop Advisory Team Vol. 22: 18.
- Wise, J. C., Gut, L. J., Isaacs, R., Schilder, A. M. C., Sundin, G. W., Zandstra, B., Hanson, E., and Shane, B. 2007. Michigan Fruit Management Guide 2008. Extension Bulletin E-154. Michigan State University, East Lansing, MI.
- Schilder, A. M. C., Gillett, J. M., and Sysak, R. W. 2007. Evaluating reduced-risk fungicides for anthracnose control in blueberries, 2006. Plant Disease Management Reports 1:SMF014.
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Progress 08/01/05 to 07/31/06
Outputs
The overall goal of this project is to expand integrated disease management options for highbush blueberry production using real-time disease risk advisories based on weather conditions and disease scouting. The specific objectives are to: 1) Develop and evaluate an advisory for mummy berry control based on scouting for apothecia and the role of frost in shoot infection; 2) Develop and evaluate an advisory for anthracnose control based on the relationship between key environmental variables and spore release; 3) Develop and validate a predictive model for anthracnose fruit infection based on thresholds of leaf wetness duration at different temperatures; and 4) Demonstrate the use of real-time advisories to growers and document changes in disease control practices as a result of the advisories. To determine whether freezing increases susceptibility of highbush blueberry shoots to infection by Monilinia vaccinii-corymbosi, potted plants (cv. Bluehaven) at green tip were
frozen at -0.5, -1.0, -1.5, and -2.0 degrees C for 1 hour followed by inoculation with ascospores. There was a linear increase in shoot strike incidence (0.4, 1.2, 3.4, and 3.8%, respectively) with decreasing temperature (P=0.07), suggesting that frost predisposes young shoots to infection. No shoot strikes were observed in non-frozen plants. A frost-guided spray program (7-10 day schedule with a fungicide application within 24 h of a frost if the last spray was more than 5 days ago) was compared to a regular 7-10-day schedule for control of mummy berry in 2005 and 2006. Fungicide treatments were applied with a CO2 sprayer at 55 psi to 4-bush plots in an RCBD with 4 replications. In both years, there was only one frost event during the study period. The frost-guided program tended to perform consistently (but not statistically) better than the regular spray schedule. Release of C. acutatum conidia was monitored using rain traps in two and three Jersey fields in 2005 and 2006,
respectively. Rainwater samples were collected weekly throughout the season. In both years, large peaks in spore dispersal did not occur until the end of the season, probably due to extended warm, dry conditions around bloom. To determine requirements for infection of blueberry fruit (cv. Jersey) by Colletotrichum acutatum berries on potted plants and detached twigs, and detached berries were inoculated and incubated at different leaf wetness durations and temperatures. In the potted-plant experiments, the highest infection incidence occurred at 25 degrees C. In general, infection incidence increased up to 48 h of wetness, but a minimum of 12-18 h of wetness was needed for infection at the optimum temperature. In the twig and detached fruit experiments, similar trends were seen, but background inoculum and possible spore survival between inoculation and evaluation affected the results. Several new weather stations were installed in the blueberry-growing region of Michigan as part of
the Michigan Automated Weather Network and will be useful for application and validation of models that will be developed in this project.
Impacts
We expect that by the end of the project we will have developed practical risk advisories that will reliably guide disease control decisions by highbush blueberry growers in Michigan. We expect to have incorporated the models in the MSU blueberry and Michigan Agriculture Weather Network websites. As the network is expanded with additional weather stations, more growers will be able to make use of the risk advisories. We anticipate that the models will help growers reduce pesticide use overall, and that they will get better disease control in the process, enhancing the quality and value of fruit produced in Michigan. This will positively benefit the blueberry industry by reducing input costs as well as worker, consumer, and environmental exposure to crop protection chemicals. An additional benefit will be an increased understanding of the biology of blueberry pathogens and increased confidence of blueberry growers in their disease control efforts.
Publications
- Schilder, A.M.C., Gillett, J.M., and Sysak, R.W. 2006. Evaluation of fungicides for control of mummy berry in Rubel blueberries, 2005. Fungicide and Nematicide Tests 61:SMF023.
- Schilder, A.M.C., Gillett, J.M., and Sysak, R.W. 2006. Evaluation of fungicides and dormant sprays for control of mummy berry in blueberries, 2005. Fungicide and Nematicide Tests 61:SMF024.
- Wise, J.C., Gut, L.J., Isaacs, R., Schilder, A.M.C., Zandstra, B., Hanson, E., and Shane, B. 2005. Michigan Fruit Management Guide 2006. Extension Bulletin E-154. Michigan State University, East Lansing, MI.
- Schilder, A. 2005. Control of fruit rots in blueberries after bloom. Fruit Crop Advisory Team Alert 20 (10):4-5.
- Schilder, A. 2005. Small fruit diseases during the 2005 growing season. Fruit Crop Advisory Team Alert 20 (18):1-3.
- Schilder, A., and Grube, B., 2005. Monitoring and control of mummy berry in blueberries. New Hampshire Cooperative Extension Bulletin, 2005.
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