Predicting the risk of cucurbit downy mildew in the eastern United States using an integrated aerobiological model

  • K. N. Neufeld
  • A. P. Keinath
  • B. K. Gugino
  • M. T. McGrath
  • E. J. Sikora
  • S. A. Miller
  • M. L. Ivey
  • D. B. Langston
  • B. Dutta
  • T. Keever
  • A. Sims
  • P. S. Ojiambo
Original Paper

Abstract

Cucurbit downy mildew caused by the obligate oomycete, Pseudoperonospora cubensis, is considered one of the most economically important diseases of cucurbits worldwide. In the continental United States, the pathogen overwinters in southern Florida and along the coast of the Gulf of Mexico. Outbreaks of the disease in northern states occur annually via long-distance aerial transport of sporangia from infected source fields. An integrated aerobiological modeling system has been developed to predict the risk of disease occurrence and to facilitate timely use of fungicides for disease management. The forecasting system, which combines information on known inoculum sources, long-distance atmospheric spore transport and spore deposition modules, was tested to determine its accuracy in predicting risk of disease outbreak. Rainwater samples at disease monitoring sites in Alabama, Georgia, Louisiana, New York, North Carolina, Ohio, Pennsylvania and South Carolina were collected weekly from planting to the first appearance of symptoms at the field sites during the 2013, 2014, and 2015 growing seasons. A conventional PCR assay with primers specific to P. cubensis was used to detect the presence of sporangia in rain water samples. Disease forecasts were monitored and recorded for each site after each rain event until initial disease symptoms appeared. The pathogen was detected in 38 of the 187 rainwater samples collected during the study period. The forecasting system correctly predicted the risk of disease outbreak based on the presence of sporangia or appearance of initial disease symptoms with an overall accuracy rate of 66 and 75%, respectively. In addition, the probability that the forecasting system correctly classified the presence or absence of disease was ≥ 73%. The true skill statistic calculated based on the appearance of disease symptoms in cucurbit field plantings ranged from 0.42 to 0.58, indicating that the disease forecasting system had an acceptable to good performance in predicting the risk of cucurbit downy mildew outbreak in the eastern United States.

Keywords

Aerobiological modeling system Cucurbit downy mildew Risk prediction True skill statistic ROC analysis Spore deposition 

Notes

Acknowledgements

This work was supported by grants from the United States Department of Agriculture-National Institute of Food and Agriculture (USDA-NIFA) OREI Award 2012-51300-20006 and USDA-NIFA RIPM Awards 2012-34103-19622 and 2012-41530-19623.

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Copyright information

© ISB 2017

Authors and Affiliations

  • K. N. Neufeld
    • 1
  • A. P. Keinath
    • 2
  • B. K. Gugino
    • 3
  • M. T. McGrath
    • 4
  • E. J. Sikora
    • 5
  • S. A. Miller
    • 6
  • M. L. Ivey
    • 6
    • 7
  • D. B. Langston
    • 8
  • B. Dutta
    • 9
  • T. Keever
    • 1
  • A. Sims
    • 10
  • P. S. Ojiambo
    • 1
  1. 1.Center for Integrated Fungal Research, Department of Entomology and Plant PathologyNorth Carolina State UniversityRaleighUSA
  2. 2.Department of Plant and Environmental SciencesClemson UniversityCharlestonUSA
  3. 3.Department of Plant Pathology and Environmental MicrobiologyPennsylvania State UniversityUniversity ParkUSA
  4. 4.Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant ScienceCornell UniversityRiverheadUSA
  5. 5.Department of Entomology and Plant PathologyAuburn UniversityAuburnUSA
  6. 6.Department of Plant PathologyOhio State UniversityWoosterUSA
  7. 7.Department of Plant Pathology and Crop PhysiologyLouisiana State UniversityBaton RougeUSA
  8. 8.Tidewater Agricultural Research and Extension Center, Department of Plant Pathology, Physiology and Weed ScienceVirginia Polytechnic Institute and State UniversitySuffolkUSA
  9. 9.Department of Plant PathologyUniversity of GeorgiaTiftonUSA
  10. 10.State Climate Office of North CarolinaNorth Carolina State UniversityRaleighUSA

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