EAST LANSING, Mich. — Using last year’s calendar or worse yet, your memory, to predict pest outbreaks and schedule applications is unreliable. Michigan State University Extension recommends a better method is to use growing degree days (GDD) as a predictor of physiological plant status, writes Kevin Frank in a recent blog from Michigan State University Extension.

Since 2006, turfgrass professionals have been using GDDTracker.net to guide them in scheduling applications to predict the application timing for the suppression of annual bluegrass (Poa annua L.) seedhead production in the spring.

As the website evolved, additional models were added to predict application timing for crabgrass preemergence herbicides, spring broadleaf herbicide timing, broadleaf weed flowering, crabgrass germination and Japanese beetle adult emergence.

As the number of models increased, the use of GDDTracker has expanded from primarily turfgrass professionals to include homeowners interested in properly timing applications to their lawn.

Click MSU Extension for a more detailed discussion of using the GDDTracker.