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.
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 normally start accumulating severity values on May 1st, but in 2017 the start date was April 1. 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.
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.
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.
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.
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.
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).
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.
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.
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