Find out if weather conditions are right for downy mildew with Enviro-weather

New Enviro-weather tool helps cucurbit growers determine if weather conditions are favorable for downy mildew.

The recent change in weather has been especially favorable for downy mildew development on cucumbers and other cucurbits.  The disease organism causing downy mildew in cucurbits does not overwinter in the state of Michigan.  Each year spores arrive in the state from other locations.  The spores then move via air currents from field to field and county to county.  Once spores have arrived, the development and spread of downy mildew is influenced by local weather conditions.  In general, downy mildew prefers cool, wet and cloudy weather.  Days that are sunny, hot and dry are not favorable for the rapid development and spread of the disease. 

A new tool on Michigan State University’s Enviro-weather provides growers with a tabular summary of weather conditions that may influence downy mildew development.  Daily temperature (maximum, minimum and average), sky conditions (cloudy, partly cloudy or mostly sunny), relative humidity (minimum, maximum and average), total rainfall, and the number of hours of leaf wetness (out of 24), are listed in a table for the selected location.   Growers can use the table and to assess whether conditions in their area are conducive to downy mildew. 

To use this tool:

1.  Type into your Internet browser. 

2.  From the Enviro-weather home page (map of Michigan with yellow dots indicating the location of weather stations), select your closest station by clicking on the dot.

Michigan Enviro-weather

3.  Then click on “Vegetables” in the light green bar at the top of the page.

Enviro-weather bar

4.  A list of crops is displayed in the light-brown column to the left of the page.  Open the "cucurbits" category by clicking on it.

Michigan Enviro-weather

5.  Then click on “weather variables affecting Cucurbit Downy Mildew” to see the table. 

Michigan Enviro-weather

The table will display daily weather conditions for the last two weeks at the location you selected on the home page. If you’d like to see conditions at another Michigan location, you can change the selected weather station by using the pull-down menus at the top of the screen (“Region” and “Station”).

If you’d like to see weather conditions for a different range of dates, you can select new start and end dates using the pull-down menus.  After you have made changes to the weather station or the dates, you must click on the “execute” button to finalize those changes.  A new table with revised settings will appear. 

At the bottom of the page is a link,  “About Downy Mildew in Cucurbits,” which will take you to Dr. Mary Hausbeck’s informational web page. 

As with any other new tool, we are asking users for feedback on how to improve it.  If you have comments or questions about this, or any other Enviro-weather tool, please contact Beth Bishop, Enviro-weather Coordinator at 517 432-6520 or  Many thanks go to Dr. Hausbeck and her lab for conceiving of the idea and for their work on this new Enviro-weather tool and to Project GREEEN for providing funds for its development.

Dr. Hausbeck's work is funded in part by MSU's AgBioResearch.

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