St Augustine grass is primarily of tropical origin and is native to salty and fresh water marshes, sandy beach ridges, the outskirts of swamps and lagoons, and limestone shorelines. Though it will survive in most types of terrain, it does best in moist and reasonably fertile soil. Two things it will not stand are waterlogged areas and very dry areas, so watering St Augustine correctly is an essential dynamic to its general health.
So, speaking in loose terms, most of the problems we see in St Augustine are caused by 1) shallow or bad quality soils, and 2) improper watering procedures. To test whether the soil is bad you need to do an analysis. You can buy kits online and can either send it to a commercial lab, or get a free assessment through your local Agricultural Extension Office. Soil amendment can take a number of different tacks depending on the result, but in general an application of compost once a year is nearly always adequate to solve most problems. In terms of watering, St Augustine grass requires one half inch of water per week, but the secret is to water it deeply, then let it dry out before watering again. Optimally, this means watering once per week until the half inch total is achieved. If you are not sure how much water your irrigation system puts down, simply put an empty can or rain gauge in the middle of the lawn and see how long it takes to get to the half inch line. If you are getting a lot of run-off into the street try cycling through the system twice and half the run time per station.
Chinch bugs can cause serious damage to St Augustine lawns by feeding on the stems at the base of the leaf. At first the damage may look like drought stress with chlorotic (yellowing) areas in the full sun and then dead areas. Chinch bugs can be controlled with insecticides with two or three applications, but remember that one thing chinch bugs cannot stand is moisture. This is why they gravitate to the full sun areas of the lawn where it is driest. Therefore another solution is to apply water to the general area. This will at least discourage these horrible pests.
White grub. Formed from the larvae of June bugs, they develop in the late summer and fall just below the soil surface. When they hatch they begin feeding on the turfgrass roots. This can be a significant problem because there is no sign of any problems until grass starts dying, and when the grubs are detected they are already quite large. The real damage normally appears the following year as dead areas. To treat these pests insecticides have to be drenched into the soil so as to reach and illuminate the grub.
Brownpatch is a common problem with St Augustine caused by an invading fungi. It normally starts as a small circular area in the lawn and expands quite quickly outward. This fungi will rarely kill the grass and in a typical brownpatch circle you will see new grass springing up in the center as the fungi works its way outward, but it can seriously weaken the lawn and make some areas look stunted and patchy with weeds mixed it. Because brownpatch is a fungi it only operates in a specific pH spectrum so killing it is really quite simple. Mix up a spray of baking soda and water and apply it liberally to the effected areas (one tablespoon per gallon is adequate). Again here, the important thing to know about brownpatch is moisture. Unlike chinch bugs brownpatch loves the damp, especially when the nighttime temperature dips below seventy degrees. This is why you will see this problem in early spring or fall. In this situation try not to water the lawn overnight. Make sure the sun is up to help counter the moist conditions on the ground. If you do get this disease in your lawn it might be an indication of the turfgrasses general bad health. An application of compost in the spring every year should go a long way to solving the problem.
Unlike fungal diseases such as brownpatch, gray leaf spot and other, St Augustine Decline (SAD) is viral in nature. The SAD virus, like all viruses, is a microscopic particle found inside the cells of St. Augustinegrass. Inside the plant cell, the virus reproduces and spreads to other cells throughout the plant. As more and more cells become infected with the virus, the vigor of the plant is reduced causing a chlorotic mottling of the leaf. The early stages are sometimes confused with chlorosis. Leaves showing chlorosis caused by iron deficiency are either uniformly yellow or show characteristic yellow stripes parallel to the mid-vein of the leaf. Iron chlorosis also appears first in the new, or young leaves, whereas SAD produces the mottling in young and older leaves. Chlorosis is a problem that can be fixed by feeding iron to the plant, but SAD is by an order of magnitude worse. The disease with slowly progress over a period of years until the lawn is so weakened Bermuda grass starts to take over, or weeds. The best control is to introduce varieties of St Augustine that are resistant to the virus, such as Raleigh and Seville. These resistant types will eventually crowd out the diseased parts of the lawn. Unfortunately there is no treatment for SAD, so when installing St Augustine make sure the contractor is using a SAD resistant variety.
Steve Gilder has been following a lawn mower around for over twenty years, and as well as an unhealthy fascination with turgrass, he also likes local history
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