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Funded Project |
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Funding Program:
IPM Partnership Grants |
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Project Title:
Re-evaluate the role of water in disease prediction models of fire blight |
Project Directors (PDs):
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Lead State: CT Lead Organization: The Connecticut Agricultural Experiment Station |
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Cooperating State(s):
Massachusetts, Maine, New Hampshire, Rhode Island, Vermont |
| Undesignated Funding: $49,908 |
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Start Date: Mar-01-2019 End Date: Feb-28-2021 |
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Pests Involved: Erwinia amylovora |
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Site/Commodity: Connecticut/Apple |
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Area of Emphasis: Impact of weather on disease occurrence |
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Summary:
Fire blight, caused by a bacterial pathogen Erwinia amylovora, is listed as the #1 disease of apple by the Northeastern Fruit Pest Working Group and apple grower associations. As the pathogens enter trees through open flowers during bloom, antibiotic application to cover those flowers is the most effective and widely used chemical control in fire blight IPM. Because the replication rate of E. amylovora on apple flowers is heavily influenced by environmental factors, weather data can be integrated into disease prediction models to infer risk of disease on a given day / period of bloom. Based on the risk, antibiotics will only be used on days of high risk of infection but not on days with low risk of infection. Although the disease prediction models are of great importance, evidence has shown that their prediction accuracy requires further improvement as false positive predictions were produced in recent years. Based on our field observations, we noticed a strong correlation between water and fire blight incidences, yet none of the current models take water into consideration in determining the pathogen epiphytic growth. In this proposal, we will perform experiment validation, both in the laboratory and in the field, and use these data to improve the accuracy of the RIMpro model. Direct outcome of this grant will be an improved RIMpro model, which will lead to more effective control of fire blight and millions of dollar savings on unnecessary antibiotic sprays. Moreover, it will help to alleviate the impact of the unnecessary antibiotics on human health and the environment.
Objectives: Objective 1. Determine the risk of flower infection under different relative humidity on potted apple trees in humidity controlled growth chamber. Objective 2. Determine the impact of relative humidity on bacterial population and virulence gene expression. Objective 3. Simulate the effect of relative humidity in RIMpro in prediction of the risk of fire blight. Objective 4. Disseminate the findings to the New England apple and pear growers and provide education about using disease prediction models to guide streptomycin spray. |
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Final Report: |
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Outcomes Following the presentation, 85% of the participants said they have improved their decision-making skills in controlling fire blight. |
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Outputs We investigated the T3SS expression in epiphytic E. amylovora on stigma and hypanthium of apple flowers, under different relative humidities (RH), using fluorescence microscopy and cultural method. On stigma surfaces, T3SS was expressed in a high percentage of E. amylovora cells, and its expression promotes epiphytic growth. On hypanthium surfaces however, T3SS was expressed in fewer E. amylovora cells than on the stigma, and displayed no correlation with epiphytic growth, even though T3SS expression is essential for infection. E. amylovora cells grown on stigmatic surfaces and then flushed down to the hypanthium displayed a higher level of T3SS expression than cells grown on the hypanthium surface alone. Furthermore, cells pre-cultured on stigma before inoculation on hypanthium caused more infections than cells pre-cultured in a T3SS-repressive medium then used as inoculum, suggesting that the T3SS induction during the stigmatic epiphytic colonization may be beneficial for the subsequent infection. Finally, the epiphytic expression of T3SS is influenced by RH. Higher percentage of stigmatic E. amylovora cells expressed T3SS under high RH than under low RH. We also set up growth chamber experiment evaluating the blossom blight infection thredshold in correlation with relative humidity. We found the infection percentage of the inoculated apple flowers is positively correlated with the relative humidity. Above 70% of flowers, when maintained at 80% or higher relative humidity, developed blossom blight infection whereas less than 20% of flowers got infected when the relative humidity is 60% or below. |
Report Appendices
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