Progress 10/01/06 to 09/30/11
Outputs
OUTPUTS: The general objective of this project is to determine how environmental and turf management practices influence fungicide performance for disease control. A project designed to understand the dissipation of residual efficacy of fungicides targeted against brown patch (Rhizoctonia solani) control was initiated in 2010. Fungicides included flutolanil, polyoxin d, triticonazole, pyraclostrobin and azoxystrobin. Treatments were applied in field plots once and then sampled seven times at 3- or 4-day intervals. A bioassay method was employed to determine residual efficacy at each sample date. Preliminary results indicate that most effective fungicides maintain 90% or greater residual efficacy for at least 7 days post application. Findings were disseminated through Purdue Turf Program research reports and educational programs offered throughout the state. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Golf course turf managers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results will contribute to more effective and efficient disease control on golf course turf. Brown patch is a common and important disease affecting golf course tees, putting greens and fairways. Cosmetic and structural damage can occur from even moderate outbreaks. The disease threatens during extended periods of hot humid weather in summer, when natural recovery from brown patch outbreaks is slow. Turf managers rely on regular application of fungicides to maintain attractive and functional playing surfaces. Information that leads to adjustments in management practices for improved disease control has economic (fungicide used more efficiently) and environmental (avoidance of excessive sprays) benefits. This project will provide information that will improve turf managers' competence in selecting and scheduling fungicide applications for brown patch control.
Publications
- No publications reported this period
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: The general objective of this project is to determine how environmental and turf management practices influence fungicide performance for disease control. A comprehensive study was completed in 2008 that defined the disease control contributions associated with biofungicides. We observed negligible differences in dollar spot control when any of three biologicals (Bacillus licheniformis, Bacillus subtilis, and hydrogen dioxide) were tank mixed with the standard contact fungicide, chlorothalonil). Results show that in almost all cases the biopesticide products did not enhance fungicide efficacy and did not extend the duration of control. Findings are disseminated thorough Purdue Turf Program research reports and educational programs offered throughout the state. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: The objective of this research is to define the effects of biological fungicides for turf disease control. Targeted audiences include all forms of turf management professionals including golf course superintendents, stadium managers, and lawn care professionals. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
These results contribute to more effective and efficient disease control on golf course turf. Dollar spot is arguably the most important disease affecting golf course tees, putting greens and fairways. Cosmetic and structural damage can occur from even moderate outbreaks. Furthermore, the disease threatens throughout the entire growing season. Turf managers rely on regular application of fungicides to maintain attractive and functional playing surfaces. Information that leads to adjustments in management practices for improved disease control has economic (fungicide used more efficiently) and environmental (avoidance of excessive sprays) benefits. The biopesticide work increases awareness of ineffective products, reducing unnecessary chemical costs.
Publications
- No publications reported this period
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: The general objective of this project is to determine how environmental and turf management practices influence fungicide performance for disease control. A comprehensive study was completed in 2007 that defined the effects if application volume on dollar spot control with penetrant and contact fungicides. We observed negligible differences in disease control with a penetrant (DMI) fungicide applied at 0.75, 1.0, 1.5, and 2.0 gal/1000 sq ft. However, with the contact fungicide (chlorothalonil), disease control suffered at volumes below 1.0 gal/1000 sq ft. An investigation of interactions between a contact fungicide (chlorothalonil) and biopesticides was initiated in 2007 and continued in 2008. Results show that in almost all cases the biopesticide products did not enhance fungicide efficacy and did not extend the duration of control. Findings are disseminated thorough Purdue Turf Program research reports and educational programs offered throughout the state. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Golf Course Superintendents. Professional Lawn Care Operators. Green Industry Business Professionals and Consultants. County Extension Field Staff. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
These results contribute to more effective and efficient disease control on golf course turf. Dollar spot is arguably the most important disease affecting golf course tees, putting greens and fairways. Cosmetic and structural damage can occur from even moderate outbreaks. Furthermore, the disease threatens throughout the entire growing season. Turf managers rely on regular application of fungicides to maintain attractive and functional playing surfaces. Information that leads to adjustments in management practices for improved disease control has economic (fungicide used more efficiently) and environmental (avoidance of excessive sprays) benefits. The application volume research contributes to more effective use of fungicides. The biopesticide work increases awareness of ineffective products, reducing unnecessary chemical costs.
Publications
- McDuffee, D. and Latin, R. 2007. Influence of spray volume on fungicide efficacy for control of dollar spot on creeping bentgrass. Phytopathology 97:S73
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: A project designed to investigate factors that influence fungicide performance on golf course fairways is underway. The study evolved from observations that disease was not adequately managed on numerous golf courses where isolates of Sclerotinia homoeocarpa were sensitive to effective fungicides. Factors under investigation include the residual efficacy of commonly used fungicides, the interaction of fungicides with plant growth regulators, and fungicide deposition factors such as the application rate, interval, and spray volume. Residual efficacy and growth regulator interactions were addressed in the 2006 report. The spray volume work is underway, and research on the fungicide rates and application intervals were completed in 2007. A cost benefit analysis of fungicide rates and application intervals for dollar spot control on creeping bentgrass putting greens was conducted for two fungicides, chlorothalonil (Daconil Ultrex 82.5WG) and iprodione (Chipco 26GT 2SC). Field
trials included four rates and three intervals for each fungicide. Disease severity in field plots was assessed on 19 dates through the course of the 11 week experiment. Fungicide costs were based on wholesale price estimates for 2007. The benefit was defined as the percentage of evaluation dates that disease severity did not exceed the tolerable limit (0.25%) for creeping bentgrass putting greens. For chlorothalonil 100% control was achieved only for three rates at the 7-day application interval. Results demonstrate that low label rates can be very effective when applied at short intervals, and very efficient in terms of cost. For iprodione, results were similar, low label rates provided excellent control when applied at short application intervals. The explanation involves the amount of time that effective residues remain on or in the plant. Previous research demonstrated a sharp decline in residual efficacy of contact and penetrant fungicides 7 - 10 days after application. If
sprays are applied every 21 or 28 days, the turf remains vulnerable to infection towards the end of the spray interval. The spray volume research is in its final stages, preliminary results indicate that spray volume may be more important with contact fungicides than with penetrants. Other factors including nitrogen nutrition and cultivar susceptibility to disease will be investigated as part of an effort to reduce fungicide inputs and costs, while improving turf quality. This information is presented is normally compiled in an annual Purdue Turf Research Report. Results and interpretations are presented at educational workshops and seminars throughout Indiana and the Midwest during winter months.
TARGET AUDIENCES: Golf course managers and agrichemical company staff.
Impacts
An understanding of factors that influence fungicide performance will help golf course superintendents make informed decisions regarding the use of fungicides for disease control. The objective is to establish economically and environmentally sound approaches to disease management. Previously, research demonstrated that on some golf courses, unacceptable levels of control could be attributed to an inherent insensitivity (resistance) in the predominant pathogen population. However, there are many cases where outbreaks are severe, despite the predominance of fungicide-sensitive strains. We are interested in investigating the effects of a variety of other factors that influence fungicide performance including spray volume, interaction with growth regulators, nitrogen nutrition, and cultivar susceptibility. Knowledge of how these factors influence fungicide performance will improve disease management skills and result in less turf damage, quite likely with less fungicide.
The benefits will be described in terms of maintaining safe, attractive, high quality playing surfaces with limited expenditures and only essential amounts of fungicide applied to the environment.
Publications
- No publications reported this period
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Progress 10/01/05 to 09/30/06
Outputs
A project designed to investigate factors that influence fungicide performance on golf course fairways is underway. The study evolved from observations that disease was not adequately managed on numerous golf courses where isolates of Sclerotinia homoeocarpa were sensitive to effective fungicides. Factors under investigation include the residual efficacy of commonly used fungicides, the interaction of fungicides with plant growth regulators, and the spray volume used to deliver fungicide to the turf. A bioassay was developed to address the residual activity of contact and penetrant fungicides used for control of dollar spot on creeping bentgrass fairways. Results indicate that efficacy is significantly reduced ten days after application for all fungicides tested. Residual activity was greater for penetrant fungicides than for contact fungicides. The results support observations and experiences of turf managers regarding severe disease outbreaks before the end of
recommended application intervals. They also suggest that timing of fungicide applications with respect the onset of disease-favorable weather has a significant influence on fungicide performance. The interaction between fungicides and plant growth regulators resulted in different trends for contact and penetrant products. Preliminary results show that expected turf recovery from a dollar spot outbreak was delayed if trinexapac-ethyl (common plant growth regulator) also was applied. From the perspective of preventative approaches for disease control, the plant growth regulator did not influence disease development or fungicide performance. The spray volume research is in its initial stages, but initial results indicate that levels of disease control were significantly reduced where the volume of water used to deliver fungicides was less than 1.5 gal per 1000 square feet. Other factors including nitrogen nutrition and cultivar susceptibility to disease will be investigated as part of
an effort to reduce fungicide inputs and costs, while improving turf quality
Impacts
An understanding of factors that influence fungicide performance will help golf course superintendents make informed decisions regarding the use of fungicides for disease control. The objective is to establish economically and environmentally sound approaches to disease management. Previously, research demonstrated that on some golf courses, unacceptable levels of control could be attributed to an inherent insensitivity (resistance) in the predominant pathogen population. However, there are many cases where outbreaks are severe, despite the predominance of fungicide-sensitive strains. We are interested in investigating the effects of a variety of other factors that influence fungicide performance including spray volume, interaction with growth regulators, nitrogen nutrition, and cultivar susceptibility. Knowledge of how these factors influence fungicide performance will improve disease management skills and result in less turf damage, quite likely with less fungicide.
The benefits will be described in terms of maintaining safe, attractive, high quality playing surfaces with limited expenditures and only essential amounts of fungicide applied to the environment.
Publications
- Latin, R. 2006. Residual efficacy of fungicides for control of dollar spot on creeping bentgrass. Plant Dis. 90:571-575.
- Stewart, J.M., and Latin, R. Influence of trinexapac-ethyl on performance of fungicides for control of dollar spot on creeping bentgrass. 2005 Annual Meeting Abstracts [ASA/CSSA/SSSA/CSSS]. 2005, p. [1].
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Progress 10/01/04 to 09/30/05
Outputs
A project designed to investigate factors that influence fungicide performance on golf course fairways is underway. The study evolved from observations that disease was not adequately managed on numerous golf courses where isolates of Sclerotinia homoeocarpa were sensitive to commonly used fungicides. Factors under investigation include the residual efficacy of commonly used fungicides, the interaction of fungicides with plant growth regulators, and the spray volume used to deliver fungicide to the turf. A bioassay was developed to address the residual activity of contact and penetrant fungicides used for control of dollar spot on creeping bentgrass fairways. Results indicate that efficacy is drastically reduced ten days after application for all fungicides tested. Efficacy half lives for contact fungicides ranged from 6 to 9 days. Efficacy half lives for penetrant fungicides ranged from 10 to 15 days. The results support observations and experiences of turf managers
regarding severe disease outbreaks before the end of recommended application intervals. They also suggest that timing of fungicide applications with respect the onset of disease-favorable weather has a significant influence on fungicide performance. The interaction between fungicides and plant growth regulators resulted in different trends for contact and penetrant products. Preliminary results show that expected turf recovery with a penetrant fungicide was significantly delayed if plant growth regulators also were applied. The spray volume research is in its initial stages, but initial results indicate that levels of disease control were significantly reduced where the volume of water used to deliver fungicides was less than 1.5 gal per 1000 square feet. Other factors including nitrogen nutrition and cultivar susceptibility to disease will be investigated as part of an effort to reduce fungicide inputs and costs, while improving turf quality.
Impacts
An understanding of factors that influence fungicide performance will help golf course superintendents make informed decisions regarding the use of fungicides for disease control. The objective is to establish economically and environmentally sound approaches to disease management. Previously, research demonstrated that on some golf courses, unacceptable levels of control could be attributed to an inherent insensitivity (resistance) in the predominant pathogen population. However, there are many cases where outbreaks are severe, despite the predominance of fungicide-sensitive strains. We are interested in understanding a variety of other factors that influence fungicide performance including spray volume, interaction with growth regulators, nitrogen nutrition, and cultivar susceptibility. Knowledge of how these factors influence fungicide performance will improve disease management skills and result in less turf damage, quite likely with less fungicide. The benefits
will be described in terms of maintaining safe, attractive, high quality playing surfaces with limited expenditures and only essential amounts of fungicide applied to the environment.
Publications
- No publications reported this period
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Progress 10/01/03 to 09/29/04
Outputs
The investigation of the epidemiology of gray leaf spot on perennial ryegrass was continued with a survey of perennial ryegrass golf courses and athletic fields in Indiana. Confirmed outbreaks occurred in Jeffersonville and Bloomington. Disease developed in West Lafayette only after infected turf was transplanted into a stand of perennial ryegrass at the Purdue Turfgrass Research Center. Despite one of the coolest summers in the past two decades, significant damage was attributed to gray leaf spot epidemics. We demonstrated that pathogen populations are diminished extensively during midwestern winters. The summer of 2004 was preceded by a relatively mild winter, thereby increasing the opportunity for pathogen survival. These observations support our contention that the disease will increase and spread over a broad range of environmental conditions, and that in the lower Midwest, the survival of the pathogen population is the limiting factor in the development of gray
leaf spot epidemics. A new project was initiated to investigate factors that influence fungicide performance on golf course fairways. The study evolved from observations that disease was not adequately managed on numerous golf courses where isolates of Sclerotinia homoeocarpa were sensitive to commonly used fungicides. One part of the research addresses the residual activity of protectant and penetrant fungicides used for control of dollar spot on creeping bentgrass fairways. Preliminary results of a bioassay indicate that fourteen days after application effective deposits were not detectable for any of the fungicides tested. Protectant fungicides appeared to begin to lose residual efficacy after 7 days, and effective levels of penetrant fungicides were diminished after 10 days. It is presumed that regular mowing (three times per week)influences fungicide performance by removing active ingredient from growing turf and influences fungicide performance. The results suggest that timing
of fungicide applications with respect to the onset of disease-favorable weather has a significant influence on fungicide performance. The bioassay will be repeated during the next growing season and other factors, such as the use of plant growth regulators will be investigated.
Impacts
Knowledge regarding pathogen survival, the fungicide sensitivity of pathogen populations, and the residual activity of common fungicides will result in more efficient use of turf chemicals and fewer, less severe disease outbreaks. Specifically, the gray leaf spot investigation will help golf course superintendents who are weighing the advantages and disadvantages associated with an approach based on chemical control vs. one involving serious renovation with non-host turf species. Also, using the fungicide sensitivity profiles, superintendents gain an awareness of the dollar spot threat on their own golf courses and often change their management practices accordingly. Finally, an understanding of factors that influence fungicide performance will help golf course superintendents make informed decisions regarding the use of fungicides for disease control. Previously, research demonstrated that on some golf courses, unacceptable levels of control could be attributed to an
inherent insensitivity (resistance) in the predominant pathogen population. However, there are many cases where outbreaks are severe, despite the predominance of fungicide-sensitive strains. We are interested in understanding other factors that influence fungicide performance. By using fungicides judiciously and in a timely fashion, turf managers are likely to apply less fungicide while maintaining safe, attractive, high quality playing surfaces.
Publications
- No publications reported this period
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Progress 10/01/02 to 09/30/03
Outputs
Two projects were completed during the past year. The investigation of the epidemiology of gray leaf spot of perennial ryegrass addressed the over winter survival of the pathogen in the Midwest. Results demonstrate that the pathogen will over winter on infested residue in north central Indiana, but population levels are too low to contribute to the epidemics during the summer. It appears that the experimental site exists within a transition zone between a southern region (Ohio Valley and lesser latitudes) where gray leaf spot outbreaks are chronic; and a northern region (all northern tier Midwestern states) where the disease has not been observed. The information will help turf managers with decisions regarding gray leaf spot control with fungicides, or avoiding the disease by converting athletic fields and golf course fairways to non-host turf species. During the course of the project, a PCR method was developed for rapid identification of the pathogen in host
tissues. We also completed a survey of isolates of Sclerotinia homoeocarpa from Indiana golf courses for sensitivity to three fungicides: iprodione, propiconazole, and thiophanate-methyl. A fungicide sensitivity profile was completed for each participating golf course. Results showed that considerable insensitivity to all three fungicides exists in Indiana populations of S. homoeocarpa. Insensitivity (fungicide resistance) appeared to play a role in dollar spot outbreaks on several golf courses. This information will help golf course superintendents make informed decisions regarding fungicide selection for dollar spot control, and help them develop a sound long term strategy for managing fungicide resistance.
Impacts
Knowledge regarding pathogen survival and the sensitivity of pathogen populations to common fungicides will result in more efficient use of turf chemicals and fewer, less severe disease outbreaks. Specifically, this information will help golf course superintendents who are weighing the advantages and disadvantages associated with an approach based on chemical control vs. one involving serious renovation with non-host turf species. Also, using the fungicide sensitivity profiles, superintendents gain an awareness of the dollar spot threat on their own golf courses and often change their management practices accordingly. As a result, they are likely to apply less fungicide while maintaining an attractive high quality playing surface.
Publications
- Brownback, L., and Latin, R. 2002. Survey of isolates of Sclerotinia homoeocarpa in Indiana for sensitivity to three fungicides. Phytopathology 92:S10.
- Harmon, P. F., Dunkle, L. D., and Latin R. 2003. A rapid PCR-based method for the detection of Magnaporthe oryzae from infected perennial ryegrass. Plant Dis. 87:1072-1076.
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Progress 10/01/01 to 09/30/02
Outputs
This research involves an investigation of the epidemiology and management of Magnaporthe.oryzae (formerly M. grisea) associated with infested perennial ryegrass in the midwestern U.S. Objectives included,1, investigation of over-winter survival of the pathogen in three environmental regimes, 2, identification of periods of pathogen activity on perennial ryegrass in the field, and 3, a PCR-based method for detecting the pathogen in infected tissues. Results to date show that survival of M. oryzae on infested perennial ryegrass residue was significantly reduced after exposure to ambient field conditions from November to May compared to exposure in dry controlled-environment conditions. Dry exposure to temperature regimes that mimicked surface temperatures during winter and spring resulted in similar levels of survival as dry residue exposed to constant 23 C for the same time period. These results suggest that temperature is not the only factor that determines the
extent of survival. It is likely that moisture and microbial activity on the infested residue also influence over-winter survival. A Burkard air-sampling device was used to determine initial periods of pathogen activity in a stand of inoculated perennial ryegrass. Although conidia were detected in early July in 2001 and 2002, symptoms did not develop at the experimental site. During those summers, the disease occurred sporadically throughout Indiana. It is possible that the pathogen survives the winter in north central Indiana with infested residue, but that primary inocula for summer outbreaks are windblown conidia produced by epidemics that occur on more southern stands of perennial ryegrass. The field research project is entering its third year.
Impacts
Survival through winter, albeit at low levels, suggests that primary inoculum for summer outbreaks of gray leaf spot is produced on infested ryegrass residue within stands of perennial ryegrass. However, it is also possible that surviving inoculum has little or no effect on epidemics in north central Indiana, and that primary inoculum is represented by airborne conidia that are produced by epidemics further south. Determination of the source of primary inoculum will contribute towards improved gray leaf spot management practices. Fungicide application tactics are likely to differ if primary inoculum is not produced from local infested residue. Knowledge regarding pathogen survival and the source of primary inoculum will result in more efficient use of fungicide and fewer, less severe outbreaks in Indiana.
Publications
- Harmon, P., and Latin, R. 2002. Over-winter survival of Magnaporthe oryzae on perennial ryegrass in the Midwest: disease management implications. Phytopathology 92: S34.
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Progress 10/01/00 to 09/30/01
Outputs
This research involves an investigation of the ability of M. grisea associated with infested perennial ryegrass to survive winter conditions typical of the Midwest. Specific objectives included,1, investigation of pathogen survival in three environmental regimes over a six month sampling period, 2, determination of the influence of temperature on short term pathogen survival, and 3, identification of periods of pathogen activity on perennial ryegrass in the field. Results to date show that survival of M. grisea on infested perennial ryegrass residue was significantly reduced after exposure to ambient field conditions from November to May compared to exposure in dry controlled-environment conditions. Dry exposure to temperature regimes that mimicked surface temperatures during winter and spring resulted in similar levels of survival as dry residue exposed to constant 23 C for the same time period. These results suggest that temperature is not the only factor that
determines the extent of survival. It is likely that moisture and microbial activity on the infested residue also influence over-winter survival. A Burkard air sampling device was used to determine initial periods of pathogen activity in a stand of inoculated perennial ryegrass. Conidia were detected in early July, soon after infested residue was introduced into the ryegrass turf surrounding the Burkard unit. Pathogen activity, as determined by the number of conidia collected with the sampling device, increased steadily through July and August until it reached a maximum in early September. By then, the stand of perennial ryegrass turf at the experimental site was seriously damaged by the disease, and it coincided with reports of outbreaks on perennial ryegrass fairways on golf courses in north central Indiana. The research currently is beginning its second year.
Impacts
Survival through winter, albeit at low levels, suggests that initial inoculum is produced on infested ryegrass residue within stands of perennial ryegrass. The detection of pathogen activity (via spore trapping) nearly two months prior to the appearance of obvious turf damage supports our premise that the pathogen does not survive well through midwestern winters and that low survival capacity influences the progress of gray leaf spot epidemics during summer months. The long lag phase of the epidemic could have important disease management implications. At our field research site, symptoms were detected in mid-July, but only after careful examination of individual leaf blades. Most turf managers would not discover infected turf until damage is clearly evident. At that time, initiation of fungicide applications for gray leaf spot control may have disappointing results. However, if turf managers applied remedial treatments at the first sign of pathogen activity rather
than when outbreaks are apparent from a distance, it is probable that satisfactory control will be achieved with less fungicide.
Publications
- Harmon, P. Rane, K. Ruhl, G. Latin, R. 2000. First report of gray leaf spot on perennial ryegrass in Indiana. Plant Dis. 84 (4): 492.
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Progress 10/01/99 to 09/30/00
Outputs
The research was designed to investigate options for avoiding or reducing the potential severity of take all patch, caused by Gaeumannomyces graminis f. sp. avenae (Gga), on creeping bentgrass before they occur. Experiments were conducted to investigate the influence of fungicide and treatments to modify root zone pH on the severity of take all patch. Prior to seeding, aluminum sulfate was lightly incorporated into the top 1 - 2 inches of the root zone mix to achieve target pH levels of 5.5, 6.5, and 7.5. After the turf was established, subplots were treated periodically with ammonium sulfate (21-0-0) or a complete fertilizer (18-4-10) and fungicide (propiconazole at 0.5 oz ai/1000 sq ft) in fall and spring. Plots were inoculated by introducing Gga-infested millet seed into the turf after a 1" deep soil core was removed from 3 sites in each treatment plot. Treatment performance was evaluated by indexing the degree of take all patch development around the inoculation
sites each month during the growing season. In 1999, take all patch symptom expression was significantly reduced by all treatments, including the aluminum sulfate treatment used to acidify the root zone mix prior to seeding. Results from 2000 showed that root zone pH returned to that of the initial root zone mix (approximately 7.5), and that the pH factor did not influence take all patch development two years after the aluminum sulfate application. The only treatments that significantly suppressed disease development involved fungicide applications in April and May. There also appeared to be no influence of pH on fungicide performance. However, periods of weather conditions favorable for take all patch development were brief, and disease outbreaks were moderate to slight. The project will enter its fourth year (out of five) in 2001.
Impacts
Results of this research will provide increased awareness among golf course superintendents to the influences of fungicide applications and acidifying fertilizer treatments on the development of take all patch of creeping bentgrass. Superintendents may use knowledge generated by this research to direct their take all patch control efforts and resources during spring months, when the pathogen is most active. Identification of appropriate and effective treatment windows will result in more efficient use of fungicide and fertilizer. Benefits are associated with the reduction of chemical inputs without increasing risk of unacceptable disease outbreaks.
Publications
- No publications reported this period
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Progress 10/01/98 to 09/30/99
Outputs
The research was designed to investigate options for avoiding or reducing the potential severity of take all patch, caused by Gaeumannomyces graminis f. sp. avenae (Gga), on creeping bentgrass before they occur. Experiments were conducted to investigate the influence of fungicide and treatments to modify root zone pH on the severity of take all patch. Prior to seeding, aluminum sulfate was lightly incorporated into the top 1 - 2 inches of the root zone mix to achieve target pH levels of 5.5, 6.5, and 7.5. After the turf was established, subplots were treated periodically with ammonium sulfate (21-0-0) or a complete fertilizer (18-4-10) and fungicide (propiconazole at 0.5 oz ai/1000 sq ft) in fall and spring. Plots were inoculated by introducing Gga-infested millet seed into the turf after a 1" deep soil core was removed from 3 sites in each treatment plot. Treatment performance was evaluated by indexing the degree of take all patch development around the inoculation
sites each month during the growing season. Preliminary results show that fungicides and fertilizer significantly affected take all patch development. Also, over a 4 month evaluation period, significant differences in disease development were associated with target pH plots of 5.5 (least disease), 6.5, and 7.5 (greatest disease). By altering the pH in the top one or two inches of substrate (prior to establishment of creeping bentgrass turf) to levels that do not favor pathogen growth and disease development it appears that the likelihood of severe take all patch development may be lessened significantly.
Impacts
If preliminary results are verified, then outbreaks of take-all patch may be reduced to an extent where the disease will be more effectively and efficiently managed with other treatments.
Publications
- No publications reported this period
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Progress 10/01/97 to 09/30/98
Outputs
Controlled environment experiments were conducted to determine the relationship between temperature, leaf wetness duration, and infection of perennial ryegrass by Rhizoctonia solani. Infection of grass plants raised in pots and exposed to a source of active R. solani mycelium were evaluated at various combinations of temperature and leaf wetness duration. Temperatures included 15, 18, 21, 24, and 27 C. Leaf wetness periods were 9, 12, 15, 18, and 24 h. Disease was most severe (more than 50 brown patch lesions per pot) when plants were in contact with the inoculum source for 24 h at 24 C. The least amount of disease (0 lesions per pot) occurred at 15 C for a 9 h wet period. The data were subject to analysis of variance with orthogonal polynomial contrasts. Significant terms were included in a regression model that described the relationship between temperature and wetness and infection. The polynomial model included linear and quadratic terms for temperature and
wetness duration. The model adjusted coefficient of determination was 0.93, indicating an excellent fit to the data. The model is intended for use in an improved brown patch warning system for perennial ryegrass in the Midwest. The purpose of this research was to define the relationship between temperature, leaf wetness duration and disease incidence by R. solani. The results are expected to contribute towards an improved disease warning model with application against brown patch on perennial ryegrass in the Midwest.
Impacts
(N/A)
Publications
- Gross, M. K., Santini, J. B., Tikhonova, I., and Latin, R. 1998. Influence of temperature and leaf wetness duration on infection of perennial ryegrass by Rhizoctonia solani. Plant Disease 82:1012-1016.
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Progress 10/01/96 to 09/30/97
Outputs
This research concerned the survival of the bacterial spot pathogen (Xanthomonas campestris pv. vesicatoria (Xcv) in tomato transplant production facilities. Research results demonstrate that: - After a few weeks, the pathogen was not detectable on plastic trays stored in an unrefrigerated environment. - The bacteria are not likely to survive at detectable levels from one season to the next on wood, stone, and metal surfaces. - Conventional surface disinfestants are very effective in reducing the amount of contamination associated with plastic trays. These results support the conclusion that contaminated transplant production materials are not likely sources of primary inoculum contributing to severe disease outbreaks in subsequent seasons. With conventional sanitation practices, the threat posed by surviving inoculum is greatly reduced or eliminated. It appears that devastating early season outbreaks of bacterial spot are most likely instigated by inoculum introduced
with contaminated seed. Other research designed to assess the benefit of fungicides for controlling fruit and foliage diseases on tomatoes used for processing, showed that fungicides are essential for tomato production in the Midwest. Results indicated that only the 7-day fungicide application interval using chlorothalonil consistently maintained anthracnose fruit lot below the 2.5% acceptable industry threshold for whole peeled tomatoes. Benefits were expressed in terms of the return on each fungicide dollar spent. It was concluded that tomato growers can expect a $10.00 - $14.00 return for every fungicide dollar invested in their crop.
Impacts
(N/A)
Publications
- Byrne, J. M., Hausbeck, M. K., and Latin, R. X. 1997. Efficacy and economics of management strategies to control anthracnose fruit rot in processing tomatoes in the Midwest. Plant Dis. 81:1167-1172.
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Progress 10/01/95 to 09/30/96
Outputs
Models that define the relationship between infection by three melon pathogens (Alternaria cucumerina, Colletotrichum orbiculare, and Didymella bryoniae) and moisture and temperature were tested in muskmelon fields and experimental field plots in 1996. The models were programmed into a microprocessor that uses temperature and leaf wetness data to advise muskmelon and watermelon farmers when to spray for Alternaria leaf blight, anthracnose, and gummy stem blight. Farmers saved 2-4 sprays over the calendar-based 7-day spray program without increasing risk to disease. The models will be tested in a comparison of satellite-generated environmental data and data acquired from on-site instruments. Bacterial fruit blotch of watermelon is a relatively new disease that first appeared in Indiana in 1989. The bacterial pathogen, Acidovorax avenae subsp. citrulli, was introduced with contaminated watermelon seed. Greenhouses used to raise watermelon transplants from seed offer
environmental conditions that are very favorable for disease spread and increase. Growers are very concerned about disease spread in the greenhouse and the possibility of survival in the facilities from one season to the next. Factors that affect survival and spread of the pathogen in transplant production facilities were investigated. Results confirmed that the pathogen was splash-dispersed from infected to healthy plants. Eliminating overhead irrigation was the most certain method of limiting spread. Application of copper hydroxide.
Impacts
(N/A)
Publications
- Latin, R., and Evans, K. J. 1996. Development and delivery of a forecaster for Alternaria leaf blight of muskmelon. Phytopathology 86: (in press) (Abstr.).
- Latin, R., Tikhonova, I., and Rane, K. 1996. Spread of Acidovorax avenae subsp. citrulli in watermelon transplant facilities. Phytopathology 86: (in press) (Abstr.).
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Progress 10/01/94 to 09/30/95
Outputs
Models that define the relationship between infection by two melon pathogens (Alternaria cucumerina and Colletotrichum orbiculare) and moisture and temperature were tested in muskmelon fields and experimental field plots in 1995. The models were programmed into a microprocessor that uses temperature and leaf wetness data to advise muskmelon farmers when to spray for Alternaria leaf blight and anthracnose control. Farmers who used the system saved 2-4 sprays over the calendar-based 7-day spray program without increasing risk to disease. The model is being revised to provide advisories for watermelon farmers in 1996. Bacterial fruit blotch of watermelon is a relatively new disease that first appeared in Indiana in 1989. The bacterial pathogen, Acidovorax avenae subsp. citrulli, was introduced with contaminated watermelon seed. Greenhouses used to raise watermelon transplants from seed offer environmental conditions that are favorable for disease spread and increase.
Growers are very concerned about disease spread in the greenhouse and the possibility of survival in the facilities from one season to the next. Factors that affect survival and spread of the pathogen in transplant production facilities were investigated. Results confirmed that the pathogen was splash-dispersed from infected to healthy plants. Eliminating overhead irrigation was the most certain method of limiting spread. Application of copper hydroxide to seedlings also reduced spread of the fruit blotch pathogen.
Impacts
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Progress 10/01/93 to 09/30/94
Outputs
A model that defines the relationship between infection by Alternaria cucumerinaand moisture and temperature was tested in muskmelon fields and experimental field plots in 1994. The model was programmed into a microprocessor that uses temperature and leaf wetness data to advise farmers when to spray for Alternaria leaf blight control. Farmers who used the system in 1994 saved 2- 4 sprays over the calendar-based 7-day spray program without increasing risk to disease. Research was conducted to determine the relationship between Alternaria leaf blight epidemics and muskmelon quality as defined by soluble solids content (SSC). In general, SSC decreased as severity of the epidemics increased. Plots treated with fungicides to protect against disease resulted in high quality fruit as determined by SSC. Similar research is underway to investigate the effect of powdery mildew epidemics on soluble solids content of muskmelon. A project to investigate the use of host-resistance
and fungicides for control of tomato anthracnose was recently completed. Less fungicide could be used on resistant cultivars to achieve acceptable levels of anthracnose control. Further reductions in the amount of fungicide applied occurred where the weather-based model was combined with a tomato cultivar with anthracnose resistance.
Impacts
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Progress 10/01/92 to 09/30/93
Outputs
A model that defines the relationship between infection by Alternaria cucumerinaand moisture and temperature was tested in muskmelon fields and experimental field plots in 1993. Different types of environmental sensors were evaluated for their appropriateness in developing and implementing a weather-based spray schedule for control of Alternaria leaf blight. A relative humidity (RH) sensor was more consistent in defining moist periods within the crop canopy than two different leaf wetness sensors. The weather-based system using the RH sensor resulted in excellent disease control in comparative trials with calendar-based spray programs. Research was conducted to determine the relationship between Alternaria leaf blight epidemics and muskmelon quality as defined by soluble solids content (SSC). In general, SSC decreased as severity of the epidemics increased. Plots treated with fungicides to protect against disease resulted in higher quality fruit as determined by SSC. A
weather-based program for scheduling fungicide applications for control of tomato diseases was evaluated in experimental field plots in 1993. Use of the model resulted in good control of tomato anthracnose with fewer fungicide applications than the conventional fixed-interval spray schedules. Further reductions in the amount of fungicide applied occurred where the weather-based model was combined with a tomato cultivar with anthracnose resistance.
Impacts
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Progress 10/01/91 to 09/30/92
Outputs
Investigation of the influence of environmental parameters on infection of muskmelon by Alternaria cucumerina resulted in the development of a statistical model that defines the association between infection and leaf wetness duration and temperature. Relationships defined in the model were integrated with research on the persistence of fungicide on muskmelon leaves to develop a weather-based decision support system to help schedule fungicide applications. The weather-based program was tested in commercial muskmelon fields in 1992. Excellent disease control was achieved in fields sprayed according to the weather-based system with 2-3 fewer fungicide applications that the calendar-based spray schedule. Empirical models (critical point, multiple point, and AUDPC) were developed to describe an observed relationship between Alternaria leaf blight and yield loss in muskmelon. All models provided a reasonably good fit to the data, however,the critical point models appear
have the greatest potential for use in evaluating disease management decisions. A weather-based program for scheduling fungicide applications for control of fruit and foliage diseases of tomato was evaluated in experimental field plots in 1992. Use of the model resulted in good control of tomato anthracnose with fewer fungicide applications than the conventional fixed-interval spray schedules. Further reductions in the amount of fungicide applied occurred where the weather-based model was combined with a tomato cultivar with anthracno.
Impacts
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Progress 10/01/90 to 09/30/91
Outputs
Research is in progress to develop models designed to provide decision support for the control of diseases on muskmelons and tomatoes. Empirical models were developed to describe an observed relationship between Alternaria leaf blight and yield loss in muskmelon. Data used to develop and validate the models were obtained from replicated experimental field plots at two locations from 1988-1991. Critical point, AUDPC, and multiple point models were derived and tested. All models provided a reasonably good fit to the data, however, a single AUDPC model described losses at both locations whereas separate critical point and multiple point models were necessary for each location. The critical point models have potential for use in evaluating disease management decisions. Investigation of the influence of environmental parameters on infection of muskmelon by Alternaria cucumerina resulted in the development of a statistical model that defines the association between infection
and leaf wetness duration and temperature. Relationships defined in the model will be integrated with research on the persistence of fungicide on muskmelon leaves to develop a program to help schedule fungicide applications. A weather-based program for scheduling fungicide applications for control of fruit and foliage diseases of tomato was evaluated in experimental field plots in 1991. Use of the model resulted in good control of tomato anthracnose with 30% fewer fungicide applications than the conventional fixed-interval spray schedules.
Impacts
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Progress 10/01/89 to 09/30/90
Outputs
Research activity was directed towards an investigation of the persistence of fungicides on melon leaves for control of Alternaria leaf blight of muskmelon (caused by Alternaria cucumerina). A bioassay using the percentage of germinated A. cucumerina conidia as the response variable was conducted to monitor the loss of deposit over time (10 days) for two fungicides, chlorothalonil and mancozeb. Fungicide persistence was evaluated in wet and dry regimes. Results indicate that although the loss of fungicides from leaf surfaces progressed in a linear fashion, the two fungicides differed significantly with respect to the rate of loss of the deposit. Under a wet regime where leaf wetness remained constant for 12 hr each day of the test, effective levels of mancozeb were removed 5 days after application whereas effective levels of chlorothalonil were present for up to 10 days after application. It was concluded that the standard fungicide application interval of 7 days
may not be appropriate for all fungicides. Results are being included into the knowledge base of an expert system for melon disease control decisions. Related research concerns the determination of potential yield reductions caused by A. cucumerina. Multiple regression analysis was used to describe the yield reduction that results from different types of Alternaria leaf blight epidemics. Data from 44 leaf blight epidemics over the past 3 years at 2 locations were used to develop the model.
Impacts
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Progress 10/01/88 to 09/30/89
Outputs
Research activity was directed towards an investigation of the persistence of fungicides on melon leaves for control of Alternaria leaf blight of muskmelon (caused by Alternaria cucumerina). A bioassay using the percentage of germinated A. cucumerina conidia as the response variable was conducted to monitor the loss of deposit over time (10 days) for two fungicides, chlorothalonil and mancozeb. Fungicide persistence was evaluated in wet and dry regimes. Results indicate that although the loss of fungicides from leaf surfaces progressed in a linear fashion, the two fungicides differed significantly with respect to the rate of loss of the deposit. Under a wet regime where leaf wetness remained constant for 12 hr each day of the test, effective levels of mancozeb were removed 5 days after application whereas effective levels of chlorothalonil were present for up to 10 days after application. It was concluded that the standard fungicide application interval of 7 days
may not be appropriate for all fungicides. Results are being included into the knowledge base of our expert system for melon disease control decisions. Related research concerns the determination of potential yield reductions caused by A. cucumerina. Multiple regression analysis was used to describe the yield reduction that results from different types of Alternaria leaf blight epidemics. Data from 44 leaf blight epidemics over the past 3 years at 2 locations were used to develop the model.
Impacts
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Progress 10/01/87 to 09/30/88
Outputs
Research on artificial intelligence applications in disease management resulted in the development of MDMS (Muskmelon Disorder Management System), an expert system designed to diagnose infectious and noninfectious disorders of muskmelon (Cucumis melo var. reticulatus). During a consultation, the user is prompted by the computer to indicate (from a menu) types of symptoms observed. The system was validated in the field during the 1987 growing season by comparing conclusions drawn by the expert system with those of a human expert over a wide range of diagnostic problems. The computer response was correct with a 100% confidence level for more than 75% of the 81 sample cases representing 11 different diseases that were addressed by the system. The system was developed using a knowledge engineering language (Texas Instruments Personal Consultant Plus) and operates on an IBM compatible computer with a 640 k and a disk drive. The diagnostic portion of the program is expected
to be released in early 1989. A prototype decision support system was developed for muskmelon powdery mildew control recommendations. Decision rules for fungicide applications were developed from research on the relationship between mildew severity and yield loss. Rules for control recommendations are part of the MDMS knowledge base and are structured to be adaptable to other diseases.
Impacts
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Progress 01/01/87 to 12/30/87
Outputs
Research on artifical intelligence applications in disease management resulted in the development of an expert system designed to diagnose infectious and noninfectious disorders of muskmelon (Cucumis melo var. reticulatus). During a consultation, the user is prompted by the computer to indicate (from a menu) the types of symptoms observed. The system was validated in the field during the 1987 growing season by comparing conclusions drawn by the expert system with those of a human expert over a wide range of diagnostic problems. The computer response was correct with a 100% confidence level for more than 75% of the 81 sample cases representing 11 different diseases that were addressed by the system. The system was developed using a knowledge engineering language (Texas Instruments Personal Consultant Plus) and operates on an IBM compatible computer with 256 k and a disk drive. The knowledge base will be expanded to address other disorders and to provide control
recommendations for each disorder diagnosed.
Impacts
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Progress 01/01/86 to 12/30/86
Outputs
A survey of cucurbit powdery mildew species in Indiana involving 46 samples from 19 counties showed that Sphaerotheca fuliginea was predominant over Erysiphe chicoracearum. Species determinations were made by mounting fresh conidia in a KOH solution on a glass microscope slide, examining the conidia, and searching for the presence of fibrosin bodies. S. fuliginea was concluded if a sample tested positive for fibrosins. Results of experiments involving fungicidal control of powdery mildew showed that the disease caused yield loss in muskmelons and pumpkins. The extent of loss appears related to the length of the time the crop is allowed to develop without interference from powdery mildew. Research was initiated on the nature of the interaction between ozone and Alternaria leaf blight of muskmelon. Twenty-one day old seedlings of the cultivar Burpee Hybrid were exposed to three doses of ozone (0.0, 0.1, and 0.2 ppm) before and after inoculation with a conidial
suspension of Alternaria cucumerina. Results showed that infection by A. cucumerina increased where exposure to 0.1 ppm ozone occurred before inoculation. Decreased infection occurred on plants exposed to 0.1 ppm ozone after inoculation and on plants exposed to 0.2 ppm ozone regardless of the timing of the ozone treatment.
Impacts
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Progress 01/01/85 to 12/30/85
Outputs
Results of experiments onmuskmelon powdery mildew support previous suggestions that significant bulk yield losses occur only when disease onset precedes the beginning of the four week harvest period. The development of a quantitative description of the relationship between disease and yield loss was hampered by inconsistent disease assessments. Attention is being focused on establishment of more accurate disease appraisal methods via analysis of incidence/severity relationships. Other research demonstrated that incidence of Fusarium wilt of muskmelon increased where larvae of striped cucumber beetles were allowed to feed on roots growing in soil infested with the Fusarium wilt pathogen. Also, pre-emergence application of a metalaxyl fungicide was shown to significantly reduce melon seedling losses caused by Pythium spp. Research on Fusarium wilt resulted in quantitative description of wilt resistance in muskmelon. Quantification allows different levels of
resistance to be determined objectively and distinguished statistically. Quantitative descriptions of resistance can be incorporated into disease management programs by projecting wilt related yield losses for each muskmelon cultivar. Current research efforts involve integration of resistance and other disease control methods including cultural sanitation and fungicide application.
Impacts
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Progress 01/01/84 to 12/30/84
Outputs
Results of experiments on muskmelon powdery mildew support previous suggestions that significant bulk yield losses occur only when disease onset precedes the beginning of the four week harvest period. The development of a quantitative description of the relationship between disease and yield loss was hampered by inconsistent disease assessments. Attention is being focused on establishment of more accurate disease appraisal methods via analysis of incidence/severity relationships. Other research demonstrated that incidence of Fusarium wilt of muskmelon increased where larvae of striped cucumber beetles were allowed to feed on roots growing in soil infested with the Fusarium wilt pathogen. Also, pre-emergence application of a metalaxyl fungicide was shown to significantly reduce melon seedling losses caused by pythium spp.
Impacts
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Progress 01/01/83 to 12/30/83
Outputs
Emphasis has been placed on determining the relationship between the severity ofmuskmelon diseases and associated yield losses. Diseases under investigation include powdery mildew, crown blight (a foliage blight associated with a magnesium deficiency), Fusarium wilt, and injury caused by exposure to high concentrations of airborne phytotoxicants. Results of work in 1982 showed that bulk yields of early maturing varieties are not affected by powdery mildew because of the lateness of the epidemic with respect to crop development. Current efforts are aimed at exploring methods to accurately assess mildew severity on muskmelon foliage. Results of crown blight experiments indicate that although Mg may be deficient in soil and leaf tissue, supplemental foliar application of magnesium sulfate did not reduce the severity of the crown blight symptoms. In 1983 muskmelon damage, traditionally regarded as symptoms of downy mildew, was diagnosed as injury caused by airborne
phototoxicants, primarily ozone and sulfur dioxide. Damage to vines varied within and among fields in southwestern Indiana. Studies involving Fusarium wilt of muskmelon are targeted at describing potential yield losses of fields infested with the pathogen. Investigations of losses caused by fruit and foliar diseases of processing tomatoes are intended in the future.
Impacts
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Progress 01/01/82 to 12/30/82
Outputs
Quantitative assessment of yield losses caused by vegetable crop diseases. Emphasis has been placed on determining the relationship between the severity of muskmelon diseases and associated yield losses. Diseases initially under investigation are powdery mildew, downy mildew and crown blight (a foliage blight associated with a magnesium deficiency). Results from 1982 powdery mildew experiments showed that disease development late in the season was not well correlated with yield loss. Disease severities recorded at the final harvest date ranged from 5-82%, yet no signficant differences among yields were realized. This is believed to be due to the lateness of the epidemic with respect to crop development. Assuming that early epidemics will significantly decrease yields, these data suggest that powdery mildew can be adequately managed by employing methods to delay the onset of the epidemic to some particular stage of crop development. Although yield loss data associated
with downy mildew epidemics are not available, observations from field plots affected by crown blight support inferences made from powdery mildew results. Sustained foliar damage that first appared early in the season resulted in greater yield loss than later occurring damage. Models defining the disease severity-yield loss relationships will be developed as more data are obtained.
Impacts
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