Put out crabgrass pre-emergent yesterday. Couldn't believe the wealth of information I combed through in an attempt to get it right. I am absolutely not an expert and I hope someone that does this for a living will lend their advice as well. I used our ZTrak and a JD 175# pull type tow behind spreader. Was done pretty quickly. Thought I would share the information.
1. Ideal time to apply. For me, that's now. I'm using it for a two-fold purpose, both to prevent crabgrass germination as well as to try to control the bermuda grass that likes to invade my fescue lawn. Apply in early spring. Good rule of thumb is that when you start to see some weeds growing around your hardscape (like cracks in sidewalk or edges of driveway) it's time to get the crabgrass pre-emergent out. Those areas are good temperature gauges as they tend to heat up a little before the dirt. I've also heard that another good timing tool is forsythia (yellow flowered bush). When it blooms, get busy! It's also true that crabgrass seeds don't all germinate at once. Some of those seeds will remain dormant until later in the season. The take home message there is that even if you're late in putting it out, it will still do some good.
2. Find a product without fertilizer. Good luck on that one. Here's a hint. The big home warehouses probably don't have it. The benefit of purchasing separately is that the ideal timing for applying the crabgrass pre-emergent and the ideal timing for fertilization don't quite line up. At least they don't where I live. So, if I wait to put down a combo product till a little later in the season where I get the most bang for the buck with the fertilizer, the crabgrass has already germinated and it won't be as effective. Besides, I like a little control in choosing what fertilizer I use. Cost differential will get your attention, too. The product I applied this weekend (Hi-Yield Crabgrass Control) was about $100 to cover 50,000 square feet. Compare that to the brand name Scotts Turf Builder fertilizer and crabgrass preventer that costs about $200 for the same square footage.
3. Which product. Who knew there was so much decision making required here. The product I chose contains benefin and trifluralin to give a little instant control plus some residual activity as well. Besides, it will help make the bermuda grass unhappy without damaging my fescue. There are definitely other options though:
a) Pendimethylin. It works well but it will stain your hardscapes and it can be rough on new grass. It also doesn't have that residual chemical activity so it doesn't last as long in the soil. A brand name for you: Scotts Halts Crab Grass Preventer.
b) Dithiopyr. Great product. Lasts well. Can even be applied a little later than other products and still give good control if you missed your ideal window. I would have used a product with this chemical in it but couldn't find any without fertilizer. A brand name to look for is Pennington Signature Series Crabgrass Preventer or Vigoro Weed Stop Crabgrass and Weed Preventer. Just sounds expensive, doesn't it?!
c) Prodiamine. Works well but is super long lasting so you need to allow a minimum of 6 months before any reseeding after application. A brand to look for is Ferti-loam All Season Crabgrass and Weed Preventer.
Hope the info is helpful. I'll post pics when I see what happens in the coming weeks. Let's hope they aren't pics of crabgrass!