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Crabgrass Preemergent Strategies for Cool Season Grasses
The weather outside is frightful. In fact, as I write this, the northeast is getting hit with our first major winter storm. My toes are still frozen from shoveling snow so trying to think about crabgrass germination seems a bit absurd. However, soon enough we will be faced with the bloom of spring and another year of trying to get ahead of the crabgrass. Given that we have had some really bad crabgrass seasons of late, here are some considerations to help you plan for spring:
What preemergent chemistry should I use for crabgrass?
There are several choices for controlling crabgrass and they all boil down to a choice between cost, convenience and efficacy. Here is a quick run down on the major crabgrass products and some of their pros and cons.
Pendimethylin, (Pre-M®, Pendelum®) “Pendi” is a common crabgrass preemergent used in lawn and turf solutions. It’s relative low cost and reasonable efficacy has driven the popularity of this product. While cost may be attractive for the initial application, there are major drawbacks. Pendimethylin is a root inhibitor and probably has more negative effects on the roots of the grass plant than other crabgrass preemergents used at the recommended label rates. Pendi is not particularly long lived so repeat applications for crabgrass may be needed which negates the cost advantage over other products which require only one application. It can also produce severe yellow/orange staining on sidewalks and can even get tracked into the house so water it in!
Trifluralin, benefin, (Treflan®, Balan®, Team®, Team Pro®) These molecules along with Pendi are dinitroanalynins (DNAs) and are available only to turf and landscape professionals. The products have the characteristic yellow/orange color, but are not as prone to staining. For crabgrass in turf, combinations of Treflan and Balan called Team® and Team Pro® are most commonly used. Benefin is quick acting and provides early efficacy while the trifluralin is longer acting and extends the control of grassy weeds, specifically crabgrass.
Dithiopyr (Dimension®) Dimension is not in the dinitroaniline family, does not have yellow DNA color, and therefore does not stain. Dimension is also less of a root inhibitor than the DNAs. This can be particularly good after a fall overseed since there could still be immature seedlings struggling for a foothold in the lawn. With most crabgrass preemergent products, once the crabgrass has germinated there is no control. Not true with Dimension. There is early post-emergent control of crabgrass. This means you can use it later and still get good results as long as the crabgrass has not gotten past the 2-3 leaf stage. You can also use Dimension in early spring and get a jump on the crabgrass that germinates when soil temperatures reach about 55° F. for 24 – 48 hours. Dithiopyr is the most versatile and forgiving crabgrass preemergent in terms of application timing and has excellent efficacy. The active ingredient does not move much after it has been spread, so there is no leaching or negative impact on the environment. However, be sure to apply the product evenly so you don’t get skips in coverage.
Greenview Fairway Formula offers a fertilizer with crabgrass preventer which contain Dithiopyr (Dimension®) for excellent results in home lawns.
Prodiamine (Barricade®, Cavelcade®) This is another DNA with the distinction of being the least soluble and therefore a long acting product. Prodiamine can last a very long time and some professionals even use fall applications to prevent crabgrass in the following spring. Unfortunately the long residual of this product is a problem if you plan to seed and is a common pitfall for those who underestimate the residual. Prodimaine is available only to turf and landscape professionals.
Siduron (Tupersan®) This is a crabgrass preemergent solution with one huge benefit – selective control of crabgrass while allowing cool season grass seed to germinate. That’s right, you can seed and prevent crabgrass at the same time! If you seed or overseed in spring, look for a starter fertilizer and Tupersan combination like Greenview Seed Starter Fertilizer plus Crabgrass Preventer. Once your new seed is up and running a follow up application is in order as the Tupersan residual lasts 4 to 6 weeks and crabgrass seed will germinate into the summer.
What rate of crabgrass preemergent should I use?
The only official advice I will give here is “consult your local university and read the label”! Here are some basic rules. First cheat at your own risk. Too many times I have seen professionals and homeowners opt for low rates to reduce cost, only to get very poor results because the active ingredient per acre is not enough to give good crabgrass control. This is very common when we are lured into a false sense of security by one or two seasons of low crabgrass pressure. You might get away with applying low rates, and you might save some money, but don’t expect good results if you are not following the manufacturers recommended use rate.
How should I apply my crabgrass preemergent?
How you apply the crabgrass preemergent will be largely a function of your overall application strategy. Some homeowners are willing to invest effort and expense for liquid solutions, but most are not. I think that granular combination products are the most practical for homeowners and require a small investment in a broadcast or drop spreader. As with any lawn product, avoid impervious surfaces to prevent runoff that finds it’s way to ground water sources. As established plants tolerate preemergents fairly well, you can often overlap applications into shrub beds without a problem. In fact these landscaped bed edges are prone to breakthrough, so covering edges are a must.
When should I apply my crabgrass preemergent?
If you are applying a combination product that includes a preemergent with a postemergent such as Greenview Fairway Formula Spring Fertilizer Weed & Feed and Crabgrass Preventer, apply it after the Forsythia has bloomed or when the first dandelion flowers appear. If you apply it too early, the preemergent runs out before the germination period is over. In the fall, apply this product when the weather cools and both the grass and weeds are actively growing, generally around Labor Day for cool season grasses.
Please remember that the Scott’s users will be putting down their fertilizer and crabgrass preventer earlier and more frequently than someone who chooses the combination products from Greenview.
See the product list below for professional quality Greenview weed control products that are available to homeowners: