Dew Point

The "Dew Point" is a very important metric in turfgrass management because it's an indicator of disease potential. Many fungi require free water for spore germination and thus we consider dew for extended periods to be a bad thing.

• Dew is moisture formed by condensation of water vapor on a cool surface. It occurs mostly at night and for our discussion, occurs on the leaf surface. 

• The dew point is the temperature at which the air can no longer hold all of its water vapor and it must condense into a liquid, in our case, as dew. Simply, it's the temperature at which dew forms.

• If the dew point is high on a summer night, say 72 degrees, it means that as the temperature cools to 72 degrees, dew forms. Therefore, the chance for disease is greater with a higher dew point for as you recall, fungi need free water for spore germination.

• With high dew points, we scout rigorously for disease and when appropriate apply fungicides to protect the turf.