Prodiamine does need to be watered in with about 1/2" of rain or irrigation, but what happens if you get a massive downpour right after you throw down? A real gully washer? Is your prodiamine application ruined and washed away? Should the prodiamine be applied again?
Prodiamine has been used for many, many years by lawn lovers and professional lawn services alike with great success and continues to be used today. In those many years, rain has been thrown down from above after an application, and sometimes nature wins, but sometimes you also need to have a little faith that the Prodiamine will do its job.
As far as reapplication, you do not want to reapply your pre-emergent. You don't know for sure if this product has been washed out a little, a lot, or not at all. So, you don't reapply because you don't know what has made it into the soil and you don't want to over-apply.
Variables such as rain are also the reason that we recommend what Allyn calls the "split application strategy" for pre-emergent in the spring. This strategy calls for an application of pre-emergent as soil temperatures cross 50 heading to 55 in the spring and a second application as temperatures cross from 60/65 into 70. The second application is your backup and will give you peace of mind in the midst of torrential rain landing in the lap of your first application. If the rain comes for your second application, you can have peace of mind knowing that your first round of pre-emergent was thrown down. In the fall, you have the winter cold as nature's backup for killing off any of the weeds your pre-emergent wasn't able to stop.
*Please note that the above information also applies to the pre-emergent Dithiopyr.
For more information on this, please see the video below:
Click HERE for our FREE Pre-Emergent Guide
Keywords: Prodiamine, pre-emergent, preemergent, rain, washed away, reapply, Dithiopyr