Michael Womack
| News | Sports | Business | Opinions | Columns | Entertainment |
| Science/Technology | Weather | Archives | E-mail Us |

Saturday, January 29, 2000

Now time to battle grassburs

Key to victory against stubborn foe in turf wars is to attack early, often

 

Our warm season turf grasses are dormant during these cooler winter months. Although most homeowners are thankful for the respite from mowing, a new battle seems to be emerging in lawns in the wake of weekly mowing. The enemy is grassburs.
   Grassburs or sandburs are annual grassy weeds which can be a serious lawn problem. They can be found anywhere but are most prevalent in sandy soils.
   The grassbur life cycle begins in early spring when temperatures stimulate the dormant burs - the actual seed - to germinate. After a few months of growth and development, spiny seed heads appear. Grassburs will die after producing seed during the first hard freeze. Unfortunately, our mild winter and lack of significant freezing weather is allowing last year's crop of burs to build up reinforcements for this spring's turf wars.
   When we see the burs or get pricked by the tiny menace, we realize there is a problem. Unfortunately, by then it may be too late to quickly get the problem under control. The proverb of "one year's seed is seven years' weeds" seems to hold true for this pest. Allowing the weed to generate seeds will produce several future generations of weeds, sometimes over several years. Remember that one of the keys to successfully controlling any weed is keeping your lawn mowed to prevent weeds from going to seed!
   Controlling this weed is often difficult and there is no "one-shot" cure-all. A systemic approach incorporating both cultural and chemical control measures will prove to be the most successful.
   Preventing seeds from germinating is the first step in breaking the life cycle. The time for this first line of defense is now, in January and early February, by use of a pre-emergent herbicide, a weed killer that prevents seeds from germinating. Once the young plants are growing, pre-emergent weed killers are no longer effective on those plants, even though they should help to prevent more seeds from emerging.
   Recommended pre-emergent turf herbicides include orazylin (Surflan), simazine, benefin (Balan), orazylin + benefin (XL herbicide), and DCPA (Dacthal). Product names will vary with the manufacturer, so check the label to make sure the product contains one of the chemicals listed. Always read the label and follow all product directions. Be sure to keep these herbicides away from trees and other plants with feeder root systems.
   As spring progresses into summer, grassburs will continue to pop up. Even if pre-emergents were used, they will eventually break down.
   Post-emergent control is dependent upon your lawn type. For those with Bermuda grass, you are in luck; MSMA, a contact herbicide, can be safely and effectively used. Unfortunately, St. Augustine grass is very sensitive to MSMA and will die if treated with this product. There is not an effective chemical control method for grassburs in St. Augustine, so hand pulling or spot treatments with glyphosate (Round-up) become your only options. If you choose to try glyphosate, be careful - it will damage all desirable turfgrasses if they come into contact with the chemical.
   During the summer months, repeat post-emergent treatments to combat any grassburs previously missed. Once seed heads start forming, use a grass catcher on your lawn to remove the stickers and reduce seed contact with the soil. Since our winter has been mild, you may need to take this action now to reduce grassbur seed heads.
   Do not use bur-infested clippings for mulch without proper composting. Compost that reaches 160 degrees will kill most weed seeds; however, most home compost bins do not reach those temperatures, so you may need to properly dispose of that yard waste.
   The bottom line for weed control is to promote a dense, healthy, weed-resistant turf through adequate and timely fertilization, frequent mowing and proper watering. Spring fertilizers should not be applied until the grass, not the weeds, is actively growing and has been mowed 2-3 times. You can safely apply a 4-1-2 ratio fertilizer which has approximately 50% slow-release nitrogen, starting in mid-March.
   Understanding the life cycle and the different control measures available will allow you to set your strategy. Then timely control measures will give you the advantage necessary to ensure victory in your turf war against this prickly menace.
   For more information on turf care, contact the Nueces County Extension Office at 767-5217.
  
  

2000 Caller-Times Publishing Company, a Scripps Howard newspaper. All rights reserved.