Seminole County Residential Horticulturist
St. Augustine grass is one of the most popular turfgrasses in Central Florida. Its tolerance to shade makes it very attractive for use in heavy landscaped gardens. Cultivars differ in their tolerance to plant pests, cold damage, and shade; you must know those differences in order to select the best cultivar for your particular needs.
Fertilization: A good all purpose lawn fertilizer for the spring is a 16-4-8 with a slow release form of nitrogen, preferable with micronutrients. Always follow the rule that nitrogen should be applied at a rate of 1 pound of actual nitrogen per 1,000 square feet. Therefore, if you use a 16-4-8 fertilizer, you need to apply 6.25 pounds per 1,000 square feet or, if you use a 10-10-10 fertilizer, you will need 10 pounds. A high maintenance fertilizer program will require 4 fertilizer applications per year. For central Florida, it means one in March, May, July and September. Iron may be applied in the summer (June) to give the grass a better color, specially, if some yellowing appears in your lawn. Apply 2 oz. of ferrous sulfate in 3 to 5 gallons of water per 1,000 square feet or use a chelated form of iron as indicated in the label.
Irrigation: Watering your lawn may be a tricky business, if you water too much you can promote diseases or if you do not water enough you can encourage insect build up or poor growth of your lawn. You should irrigate only when needed, generally, when the grass blades begin to wilt. Apply ? inches of water and do not water again until wilting starts to occur. Commonly, lawns are watered twice a week.
Weed control: A general rule to follow in weed control is to apply a pre-emergence herbicide around February 15 and post-emergence herbicides in May as needed. Do not apply herbicides if the turf is under stress of water or if air temperatures exceed 85 degrees F.
Mowing: Mowing is a very important practice and many problems arise because of improper mowing practices. Mow the lawn at 3 inches on regular varieties and 2 inches on semi-dwarf varieties. Do not remove more than 1/3 of the leaf blade in each mowing. Make sure that the blades are sharp during the mowing operation, otherwise the leaf blades will be injured more than necessary and the recovery may be slow and predispose the plant to other problems.
Pest and Diseases: St. Augustine grass is affected by many insect and disease problems. Learning to recognize their symptoms is important because if the damage is allowed to continue for a long period of time, the problem could be more difficult to control and the damage could become very expensive. Chinch bugs are probably one of the most important insects in St.
Augustine grass. The best way to control them is to use resistant varieties such as Floratam or Floralawn. There are known cases of chinch bug damage to these cultivars and therefore you should be alert of this insect even if you have a resistant variety. Other insect pests are webworm, army worms, grass loopers, and mole crickets. The most recognized diseases in St. Augustine grass are brown patch and gray leaf spot. Brown patch occurs in warm, humid weather (spring and fall months) and is associated with excessive nitrogen levels. Gray leaf spot occurs during the summer rainy season and it is also associated with high nitrogen levels. The use of fertilizers containing slow release forms of nitrogen can be used to minimize the damage caused by these diseases. Fungicides can also be used to control these diseases. Another disease, known as take-all disease, has been reported frequently in St. Augustine and other grasses. This particular disease is harder to diagnose and very difficult to control. It is usually necessary to replace damaged turf. Only systemic fungicides have some effect in controlling this disease but in many cases, because of the difficulty in identifying this disease, the affected plants are not treated early enough to provide an adequate control of the disease.
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