In my last post I mentioned that crabgrass preemergence herbicides are packaged as a percentage of the active ingredient (ai). When buying these products first check the bag for what herbicide it contains and what is the percentage of the active ingredient.

Generally the product with higher percentage of active ingredient, the smaller the bag will be by weight. The reason for this is that the application amounts are base on a recommended quantity of .25 lbs. of active ingredient per acre. This where it gets somewhat confusing and requires a simple explanation.

One of the more common herbicides formulated for home use is dithiopyr. Dithiopyr is considered both preemergence and postemergence because it will control crabgrass seedling prior to tiller development. Two examples of products sold locally are Sta-green Crab-EX 0.17% ai in a 17 lb. bag and Green Light with Dimension (dithiopyr)  0.25% ai. in a 10 lb. bag. Both products cover 5000 sq. ft.

Why? Sta-green recommends applying the product at 3.4 lb. per 1000 sq. ft thus the 17 lb bag and Green Light recommends applying the product at 2.4 lbs per 1000 sq. ft. thus the 10 lb. bag.The consumer needs to be aware of this information and base their choice on these facts. The most important thing to do when applying herbicides and fertilizer is to know the square footage of your lawn and apply the correct amount that is recommended on the label. By applying ½ the amount in one direction and ½ the amount at 90 degrees will insure complete coverage of your lawn area. The herbicide must be irrigated into the lawn by a ½ ” rainfall or by sprinkler to give good weed control.

I purchased Green Light at Virginia Beach Feed and Seed on 132 N. Witchduck Road near Cleveland Street and would recommend them for their service and knowledge.

 

Please read and follow the package label.                                                           

Apply wisely to protect the Chesapeake Bay.

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     With temperatures on the rise, daffodils showing color and life returning to normal after an unusually cold, wet winter, it’s time to think about our lawns and gardens.Our lawns major enemy is lurking just inches below the surface. The seeds from last year’s crabgrass crop are waiting for the soil to warm up to 55 degrees to germinate. This can occur in the local tidewater area very soon. My soil thermometer is reading 49 degrees today. The local weather prediction is for temperatures in the upper fifties to near sixty this week with rain later in the week.How do we stop the germination of the crabgrass seed? The only way to control crabgrass is by using a preemergence herbicide. Herbicides containing bensulide, benefin, dithiopyr, oryzalin, pendimethalin and prodiamine inhibit certain phases of cell division during seed germination. The herbicides is absorbed by the root or shoot, cell division is blocked, growth is inhibited and the immature seedling dies.Most formulations of preemergence herbicides for the homeowner are sold as a dry or granular product. Some companies incorporate the herbicide in with fertilizer but please avoid this product because as written in a previous blog, you should not fertilize in the spring. Turfgrass  preemergence herbicides essential do not leach in a downward direction beyond a depth of 2-3 ” due to binding to the soil and organic matter. The herbicide is presented as a percentage of active ingredient (ai). All of the dry formulations of herbicides are stable and maintain their activity for many years if protected from moisture.

Check out your local retailers, see what is available and make careful note of the percentage of active ingredient.

In my next blog entry, I will try to offer a simple approach to buying crabgrass preerergence and spreading it on the lawn.

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