Good afternoon and thank you for your question.  Unfortunately, I cannot confirm from the photos alone that you are dealing with white grubs.  Can you please roll back the turf and provide a photo so I can get an idea of the white grub populations you are experiencing.  

If it is grubs, it is likely too late to get this product down and taken up into the plant.  Because it is a systemic insecticide, it could take over two weeks to get taken up into the plant and be effective. Possibly even longer with the drought we have been experiencing and since the grass is not actively growing, the function of the phloem and xylem has slowed way down. Waiting for rain would even delay the process even further.

Typically at this time of year, we also also dealing with third instar larvae (the largest and final larval stage) present in the soil. It is recommended that the application is made prior to the third instar grub due to the fact that they stop feeding and descend into the soil as winter approaches.  This insecticide is much more effective when applied as a preventative verses a curative. 

Once I see the photo, I can better guide you.  Thank you again for your question.

Jen