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Seasonal Guides for Your St. Augustine Maintenance
During the fall, mowing will occur less often—keeping your St. Augustine slightly higher than the regular 2–4 inch height will encourage deeper root growth which helps it survive in colder temperatures and during winter dormancy.
Water less as temperatures drop—too much water will lead to disease. Water to prevent drought stress while grass is actively growing and after the beginning stages of dormancy to prevent dehydration.
Apply pre-emergent herbicides to fall and winter weeds like chickweed, henbit, Poa annua or purple deadnettle. Apply post-emergent herbicides only when weeds are present. Since St. Augustine is sensitive to certain herbicides (2,4-D and MSMA), use an Atrazine-based post-emergent herbicide. Follow label directions.
It’s recommended you apply a fungicide at preventative rates as this will help the grass enter colder months in a healthier condition. If you have had disease issues around this time before, you may need multiple applications in affected areas. Consider mapping those areas because fungicide treatment can be expensive. If you use a granular variety, water the lawn immediately after application to help soil absorption. A few common diseases that may be found include large patch, Cercospora leaf spot, leaf rust and Bipolaris leaf spots. If you live in South Florida, SCMV infected Floratam St. Augustine tends to develop lethal viral necrosis fall through spring.
Don’t overwater. In the active growing season, St. Augustine needs about 1 inch of water a week from natural rainfall or irrigation. If you apply any granular fertilizer or control product, you will need to water it in. This is a sufficient amount of water for the week. Overwatering may promote disease outbreak. Conduct an irrigation audit to evaluate how much water is being delivered to different areas of your lawn.
Apply a pre-emergent herbicide when soil temperatures reach 55 degrees Fahrenheit. This will prevent summer annual weeds like crabgrass and goosegrass from plaguing your lawn and garden. If you notice any current weeds, control them with a post-emergent herbicide. St. Augustine is sensitive to herbicides with 2,4-D, dicamba, MCPP and MSMA. Use a post-emergent herbicide with Atrazine as its active ingredient.
Apply a systemic fungicide at a preventive rate to keep disease from taking hold of your lawn. You may begin to see disease outbreaks as your St. Augustine begins to green up. St. Augustine may be prone to gray leaf spot at this time. Do not apply fertilizer until you’ve applied a systemic fungicide at a curative rate and your grass has recovered.
St. Augustine mowing heights during the summer generally range from about 2–4 inches. When mowing during the summer, never remove more than 1/3 of the leaf blade at a time. If you remove more than that, you will stress the grass and it may go brown for a short time. Taller blades provide more shade for your root system to stay cool and retain moisture during the hot summer days. If you are returning from vacation, you may have to mow multiple times to get the grass back to the desired height. Wait about 3–5 days between each mowing.
Do not overwater the grass. St. Augustine only needs about one inch of water weekly. Water for longer periods of time, less frequently and in the early morning hours. Take rainfall into consideration.
If drought symptoms or yellow spots occur in a sunny location, check for chinch bug activity. Push a coffee can (with both top and bottom removed) into the ground and fill it with water. Any chinch bugs present will float. Treat for chinch bugs with Bifen L/P, or Bifen XTS if you have 20 or more chinch bugs per 1,000 sq. ft. Other insects to look out for are grub worms, mole crickets, sod webworms, and fall armyworms. If you use a granular variety, water the lawn immediately after application to help soil absorption. Calculate that watering into your weekly watering amount.