Great PointLots of variables here. Some products work on several weed species, some are mainly crabgrass products. With a mild winter, the crabgrass wasn't banged much, so it's cranking now. Some products have treatment restrictions regarding applications or amounts applied per growing season. If applied too early, they may actually "play out" and by mid-summer be gone. Timing is critical to be sure. We have just started first apps as of Feb.
We have observed both root pruning and looping from Pre-emergents in SA. Seems like Dimension was exhibiting such as much as any of the other products. I guess one needs to weigh all considerations (risk vs. benefit) and make a choice. We will likely run two cycles then that's it. When it's gone it's gone. I've always felt that the one big problem with pre-emergent turf apps is...you never know for sure what the conditions would have been like had you NOT applied any (unless you do half with and half without in side-by-side comparisons). Just give it your best shot, inspect often , document your findings and then run like hell!!! LOL.Great Point
Location Location Location plays a super important part with Pre Emege. 10 to 20 miles can be weeks a part with spring flush and Pre Emege timing.
In years past I have followed the non Pre Emerge policy believing it chemically root pruned my St Augustine. Now I am trying it the other way against my original opinion of Root Pruning being more harmful than good.
Jvan -The window varies with the Zone, end of February is typical down here.
I believe the target application date may have changed in light of the weather conditions, an earlier application is indicated since seed germination is exceeding the threshold levels down here.
Problem is, what does it do to later applications and the window involved. Do you move the second application up proportionately and run the risk a later application being required and having maxed the limits? Or risk the window between applications and spot spray knowing seed has already germinated.
The reason I ask is because I'm expected to inform several HO's regarding the turf conditions and make recommendations. I haven't experienced this type of winter.
I'm inclined to recommend an immediate application now. Split the time difference between now and the next application and bank on a normal cool season this year.