Late Blight Risk Monitoring- Michigan State University
2016
Frequently Asked Questions
  1. What is Late Blight Risk Monitoring?
  2. How do I start using the Late Blight Risk Modeling Site?
  3. What do the colors of the markers on the map mean, and why are they different colors?
  4. What is the "Risk Level" and what does it mean?
  5. What are DSV's?
  6. What are the 24hr and 72hr gridded forecasts?
  7. How do you come up with your spray recommendations?
  8. How did you come up with your recommended fungicide rates?
  9. What is Volunteer Survival?
  10. What are "P values" and what are they used for?
  11. How did you get that Google Map on your website?
  12. I have a different question/problem. Who should I contact?

  1. What is Late Blight Risk Monitoring?

    Late Blight Risk Monitoring is a service provided by Michigan State University to Michigan potato growers. The objective of the program is to provide growers with up-to-date information to help them make timely and effective disease management decisions. Late blight of potato, caused by Phytophthora infestans, spreads in potato canopies by continuous leaf and stem infection when inoculum is present and favorable environmental conditions, typically moist cool weather, exist. The Late Blight Risk Monitoring website uses real-time weather data from the Michigan Agricultural Weather Network (MAWN) to estimate when conditions are most favorable for a disease epidemic and provides fungicide recommendations appropriate to that risk. For more information see: Web-interactive integration of regional weather networks for risk management of late blight in potato canopies.

  2. How do I start using the Late Blight Risk Modeling Site?

    The Late blight Risk Model predicts the first occurrence of potato late blight and its subsequent spread based on seasonal accumulation of severity values (DSV's; see the Explanations page for more details). Accumulation of severity values should start at plant emergence. In our model we start accumulating severity values on May 1st, but you can select your own emergence date using the "Calculate your own" emergence page. To start using the Late Blight Risk Modeling site just select the marker on the map that is closest to your location. It will pop up a dialogue with the Risk Level for your area, and you can click on it to get a spray recommendation for your area. Or as mentioned above you can use the "Calculate your own" page to get a personalized recommendation.

  3. What do the colors of the markers on the map mean, and why are they different colors?

    The markers on the map change color according to the risk level for that location. Markers can be green (low risk), yellow (medium risk), orange (high risk), purple (equivalent to pink; late blight seen within 2-5 miles) or red (late blight seen within 1 mile). For more information on how and when the colors change see the Explanations page.

  4. What is the "Risk Level" and what does it mean?

    The Risk Level is a estimation of whether the conditions are favorable for the initiation of a late blight epidemic and determine what the fungicide spray recommendation will be. For more information on risk levels and their corresponding spray recommendations see the Explanations page.

  5. What are DSV's?

    DSV stands for Disease Severity Value. Disease severity values are based on various combinations of the number of hours (in a given time period) with a relative humidity of 80% or greater and the average temperature during this period. They are used to predict when conditions are most favorable for disease initiation. For more information see the Explanations page.

  6. What are the 24hr and 72hr gridded forecasts?

    The new gridded forecasting models for the full state of Michigan are based on the National Weather Service National Digital Forecast Database. This data is used to predict late blight conducive conditions and calculate a risk value [0 (no risk) or 1] for 5 km grids across Michigan. The risk is calculated using a NeuroWeatherNet Model and is the latest version of an artificial neural network (ANN) based late blight risk model. The estimates of risk are based on daily predicted minimum temperature, cloud cover (AM and PM), quantity of precipitation estimates (AM and PM), hours estimated to be above the leaf wetness and temperature thresholds necessary for potato late blight development (calculated both with and without precipitation) and hourly-based estimate of overall risk for the day (calculated both with and without precipitation). For further details on this research see Baker et al., 2014, Journal of Agricultural Sciences and Baker et al., 2014, Computers and Electronics in Agriculture.

    Web-interactive integration of regional weather networks for risk management of late blight in potato canopies.

  7. How do you come up with your spray recommendations?

    Spray recommendations are based on data from field trials carried out at Michigan State University and other universities. For more information see Web-interactive integration of regional weather networks for risk management of late blight in potato canopies.

  8. How did you come up with your recommended fungicide rates?

    Recommended fungicide rates (see the Fungicide rates page) are based on field trials and the manufacturers recommended rate which can be found on the product label. For more information contact you local fungicide supplier.

  9. What is Volunteer Survival?

    Potatoes that are left in the field at harvest are known as volunteer potatoes. In areas where winter soil temperatures are not cold enough to kill tubers left in the field, they can survive the winter and become a serious weed problem the following spring (click here for more information). In addition, volunteer potatoes which survive the winter can harbor pests and diseases. Epidemics of potato late blight can be initiated from mycelium of Phytophthora infestans, which survives over winter in infected volunteer potatoes. Studies at MSU have shown that tubers of most cultivars appear to breakdown after exposure to 27°F for about one day. We have developed a model which predicts the likelyhood of tuber survival over the winter based on soil temperatures at 2 and 4 inches between November 1st and March 31st. If tubers were exposed to temperatures below 27 °F for more than 120 h between 1 November through 31 March at 4 and 2” depth then the risk of tuber survival is considered low (indicated by a green marker pin). If tubers were exposed to temperatures below 27 °F for less than 120 h at 4” depth and greater than 120 h at 2” depth then there was a moderate risk of tuber survival (indicated by a yellow marker pin). If tubers were exposed to temperatures below 27 °F for less than 120 h at 4” depth and less than 120 h at 2” depth then there was a high risk of tuber survival (indicated by an orange marker pin).

  10. What are "P values" and what are they used for?

    P values (also known as P-day values) are used to predict early blight (caused by Alternaria solani) and the need for protective fungicides. P values are cumulative and according to the model used on this site once they reach over 300 then protective sprays must be applied. See the early blight bulletin for more information.

  11. How did you get that Google Map on your website?

    You can add Google Maps to your website using the Google Maps API. For more information see the Google Maps Help page.

  12. I have a different question/problem. Who should I contact?

    This FAQ is updated periodically when new questions or issues arise. To contact us with questions/problems see the Contact Us page or email:

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Page Last Updated - 25 May 2016