The correct timing to apply preemergent for crabgrass in bermuda is an important entry in this Garden Counselor Question/Answer series, because it may contradict the product's label instructions.
I live in Central North Carolina and have bermuda grass. The turf is not great because we moved here last May and there was already a major crabgrass infestation.
My plan has always been to use pre emergent this year and hope the lawn would rejuvenate itself with the crabgrass problem under control.
Well, here I am about to apply Lesco preemergent and I read on the package do not apply the product if the turf is not thick and well established.
I don't know what to do. I can't take another year of crabgrass takeover. (March, 2016)
Garden Counselor ANSWER:
Yes, you can use preemergent-for-crabgrass-in-bermuda, even if the bermuda-grass is not lush and thriving.
You don't need to wait to improve the lawn condition, because that would be too late for the crabgrass preventer to be most successful.
I think this reply will still be in time to encourage you.
I lived in Statesville for a couple of years, so I am somewhat familiar with your weather conditions. I checked the Cronos Map at the North Carolina Climate Office for soil temperatures, and it looks like most areas in central North Carolina are still in the low 50's (soil, not air temp).
This is a great time to put down the preemergent for crabgrass if you have not already done so. If you did apply it already, you should get great results. You may have seen a small amount of crab grass sprouting already, particularly in warmer or drier areas of your yard.
But the majority of the crab-grass seeds are likely just starting to wake up, so applying within the next couple of weeks (but ASAP) should provide excellent control.
So what about the bermuda grass, and it not being thick and robust right now? Thankfully, this is a bit of a trick question or condition. If a yard has young, immature grass (newly planted seed, or new sod) then it is very vulnerable and susceptible to damage by any type of chemical.
That is not the same condition as compared to a warm season variety of grass which goes dormant during the cold seasons.
Your question suggests that the bermuda lawn has been around for a long time, but is just in poor condition with the crabgrass dominating. You can still consider it established, however, because of the bermuda having the rhizomes underground, which is the core of the individual grass plants.
You cannot hurt a dormant lawn at all by putting down preemergent for crabgrass in bermuda.
(Please Note: this statement may not be true for all types of chemical herbicides. We're just talking about weed preventers here, which stay in the very top layer of soil.)
As new growth starts to come out of the rhizomes, it is not the same process as a new seed starting to sprout. The seed sprout will have its growth interrupted. The bermuda will push right through.
Picture it like a Carolina Panthers running back (the bermuda) who is going to break thru the defensive line (the preemergent barrier) with no problem, while a San Diego Chargers running back (a grass or weed sprout) is going to get stopped in his tracks at the line of scrimmage! (Maybe that's why my current hometown team wants to relocate? -Update: enjoy Los Angeles, chumps!))
Even if some of your bermuda grass has started to green up, the same situation applies. The bermuda has an established root system, compared to an immature new lawn. Whether or not the bermuda lawn is thick is not really relevant in this case.
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Go to PREEMERGENT FOR LAWNS: A User’s Guide To Weed Preventer Products.
Go to When To Apply Crabgrass Preventer to understand more factors affecting all lawns.