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Monday, July 17, 2017

Weeds in Hybrid Bermudagrass

Q. I have a hybrid Bermudagrass lawn with weed problems of clover, crabgrass and chickweed.  I sprayed the lawn in spring with a liquid weed killer using garden hose. Weeds loved it. I bought a spreadable product which can't be applied during temperatures above the 80's.  Is there anything that I can do before the fall?  
Most high end golf courses like this one in the hot Mojave Desert climate uses hybrid bermudagrass as its base and overseeds with perennial ryegrass in the fall if the price of water permits it. Hybrid bermuda has been the grass of choice in hot climates because of its beauty and resilience.

A. Hybrid Bermudagrass, if managed correctly, will have very few weeds as a residential lawn if mowed, fertilized and watered correctly. Mowing frequently at the proper height, applying high nitrogen fertilizers every 6 to 8 weeks and watering to keep it “perky” keeps most weeds at bay.
Hybrid bermudagrass must be mowed frequently to encourage horizontal growth which is important for keeping weeds at bay. Frequent mowing creates shade on the soil which discourages weed growth. This is a Toro reel-type mower for mowing golf course fairways, greens and tees.
            Mowing height depends on the variety of hybrid Bermudagrass. All of them should be mowed below one inch and a few of them grow best when cut at ½ inch or less. Frequent mowing at these heights encourages a thick, horizontal mat of grass that prevents these weeds.
            Apply high nitrogen fertilizers every 6 to 8 weeks during its growing season, particularly in the summer months. Reduce the amount of fertilizer applied to the grass to between ½ to 3/4 of the recommended rate on the bag. Fertilizing with high nitrogen fertilizers and mowing frequently work well together to prevent weed growth.
Ammonium sulfate is a conventional mineral fertilizer high in nitrogen which promotes leaf, stem growth and dark green color.
            Irrigate during the early morning hours before sunup. Make sure to apply enough water to penetrate the soil 12 inches deep. You will be surprised at how many of these weeds will be eliminated through proper mowing, fertilizing and irrigation.
            Weed control in Bermudagrass is more effective in the spring and fall when temperatures are cooler. Weeds are more resistant to weed killers when stressed by the heat. Weeds are more susceptible to weed killers during cooler months.
Goosegrass looks very similar to crabgrass except for white radiating from the center when it is mowed. Pre-emergent weed killers must be applied about two months later to control goosegrass compared to crabgrass.
            Make sure it is crabgrass and not goosegrass. They look very similar. Crabgrass control begins mid to the latter part of January. Goosegrass control begins 2 months later. Pre-emergent weed killers are applied to the lawn to kill seed as it germinates so these weed killers must be applied before the seed germinates or you’ll get no control. Follow label directions.
Crabgrass doesn't have this white center like goosegrass and it appears much earlier in the season. Weed control for crabgrass happens very early in the spring.
            To control clover and chickweed use a liquid weed killer containing either MCPP, 2,4-D and dicamba OR MCPA, 2,4-D and triclopyr listed as ingredients on the label. Apply it either in combination with a fertilizer and applied with the drop spreader or liquid applied with a compressed air sprayer. Hoes-end applicators, in my opinion, do not do a very good job.
            Do not apply water for 24 hours after an application. Mix a wetting agent with the spray to help it get inside the leaves. Read and follow label directions.

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