Ecks from Tex said:
I use it every April along with Prodiamine and like it. You have to vary pre-emergents if you want to get in 3-4 apps per year because you can easily reach annual maximums with two applications. Prodiamine and Pennant before summer is a great combo
Your annual max remark you my attention. You can get 12 months of coverage with prodiamine, depending on how much you apply at once, just by taking the annual max and splitting it along intended quantity of applications. Why would you run into a limit otherwise? Is there a benefit to applying more than 2.30lb per year per acre, or is it an issue of the type of turfgrass?
I use preemergent aggressively. My schedule is a function of my grass and my zone along the gulf coast.
Prodiamine is an elite crabgrass control. It actually only provides "up to" 8 months of coverage. That's fine, but for me crabgrass is already germinating in January and my lawn isnt going dormant until after Dec 1. So even if apply the max, I'm not getting 12 months of crabgrass control with one product.
Further, there are diminishing returns with every preemergent. It's a function of rate and time, and ends up looking like a bell curve. So while it may provide up to 8 months of protection at the max rate, an unusual,y hot and wet summer could very easily shorten that to 6 months, with the last two only being 70% effective. So what I do is overlap 4 preemergent applications during the key germination periods. I split Prodiamine in feb and November to equal the max annual rate. I apply Dithiopyr in the early summer to provide additional protection during times when a post-emergent app would likely damage my lawn (yes, even Celsius; y'all don't know the perils of St Augustine).
I apply pennant because Prodiamine is actually not that great of a preemergent for sedges and dollar. To the extent you can control sedge germination, pennant is the elite pre em herbicide. So I apply that in April when sedge is likely to germinate. It just gives me that extra jump in protection and because the active ingredients are different it isn't going to interfere with anything.
I don't think you can hurt your lawn applying a little more than 2.3 lb/acre but I sure as heck don't recommmend it. Just as easy to find a different product and double up on protection, so you are never in a period where the protection is diminishing. It is always at its strongest, which is my goal because I want to have a program where zero post emergent herbicides are necessary.