Leonard from Matthews, Nc writes
The common product which contains Quinclorac in part does not seem effective for crabgrass in the 80-95 degree days in summer.
Quinclorac 75 DF should be applied only in temperatures below 85. You should apply in the early morening or late evening on hot temperature days. The product label does state the following regarding crabgrass: Complete control may not be achieved under certain conditions to crabgrass at 2 - 4 tiller stage. In these cases you will need to make a sequential application for control. For best results apply with methylated seed oil either before the second tiller stage or as the weed grass mataures. You should treat whenever the crabgrass has just emerged or after it has matured for best results, whenever this is in your area. You can also check with your local cooperative extension office for the best advice on timing.
Answer last updated on: 07/21/2017