St. Augustine Grass [ St. Augustine fertilization ]
Richard L. Duble, Turfgrass Specialist
Texas Agricultural Extension Service
© Richard DubleOrigin and Distribution. St. Augustine grass is a widely used lawn grass along the Gulf Coast in the U.S., in Southern Mexico, throughout the Caribbean region, South America, South Africa, Western Africa, Australia and the South Pacific and Hawaiian Islands. The species is primarily of tropical origin and is native to sandy beach ridges, fringes of swamps and lagoons, salty and fresh water marshes and limestone shorelines. St. Augustine grass gradually moved inland to naturally open sites such as streambanks, lakeshores and other moist sites. It tolerates a wide range in soil types, but does not withstand waterlogged or droughty sites.
In the U.S., St. Augustine grass is found from the Carolinas to Florida and westward along the Gulf Coast to Texas and in Southern and Central California. Because of its lack of winter hardiness, St. Augustine grass is restricted to areas with mild winter temperatures. Like bermudagrass, St. Augustine thrives in high temperatures, but the growth of St. Augustine is better than that of bermudagrass in cool, coastal climates.
St. Augustine grass is native to the Gulf of Mexico region, the West Indies and Western Africa. For as long as there have been records, St. Augustine grass has been reported as a seashore pioneer along the Atlantic coasts of Africa and the Americas. Prior to 1800, the species was reported in Uruguay, Brazil, Nigeria, Sierra Leone, the West Indies, Bermuda and South Carolina. In the Pacific, records are not nearly as old, but it was reported in Kauai prior to 1800. By 1840, St. Augustine grass had also been collected from Australia and New Zealand.
Several variants or strains of St. Augustine grass have been reported. The normal strain in early records has a white stigma color and was found to be a fertile diploid with 18 chromosomes. A sterile triploid variant with purple-colored stigmas was first collected around the Cape of Good Hope in 1791. By 1900 it was being used for lawns in Natal and has since been planted in Rhodesia, the Congo, Senegal, Australia and Southern California. In Florida it has been planted for lawns since the 1890's.
St. Augustine grass was moved inland from coastal regions by man for use in pastures and lawns. Its requirements, other than mild winter temperatures, include moist and somewhat fertile soils. St. Augustine grass will not survive in dry inland areas without supplemental irrigation. It is not as drought tolerant or cold tolerant as bermudagrass; consequently, its inland movement has been restricted to states and countries bordering coastal zones.
This species is called "St. Augustine grass" and sometimes "carpetgrass" in the Southeastern United States and in California, "crabgrass" in Bermuda and the West Indies, "gramillon" in Argentina, "wiregrass" in St. Helena and "buffalograss" in Australia and the South Pacific.
Description. St. Augustine grass, Stenotaphrum secundatum (Walt.) Kuntze, is a perennial robust grass widely used for pastures and lawns. In the warmer climates of the tropics and subtropics it rivals bermudagrass in importance.
St. Augustine grass is a coarse textured, stoloniferous species that roots at the nodes. Unlike bermudagrass, St. Augustine grass does not have rhizomes. Its stems (stolons) and overlapping leaf sheaths are generally compressed; leaf blades generally folded, abruptly contracted at the base, rounded at the tip, and smooth; ligule is reduced to a short fringe of hairs; collar is petioled and the sheath greatly compressed and ciliate along the margins. Inflorescences mostly terminal, some also axillary, spike like (corky) racemes and spikelets imbedded in main axis; each raceme bearing 1-3 spikelets; spikelets lanceolate or ovate, awnless and sessil; glumes membranous, the lower glume less than half as long as spikelet; lower floret staminate, upper floret complete and caryopsis ovate to oblong, 2.0-3.0 mm long, often failing to mature.
Adaptation and Use. St. Augustine grass is adapted to moist, coastal areas with mild winter temperatures. It is known to be tolerant of high summer temperatures, and St. Augustine grass retains its color at temperatures as much as 10° lower than those which discolor bermudagrass.
St. Augustine grass tolerates moderate shade, being as good or better than other warm season grasses for shaded sites. However, under densely shaded conditions, St. Augustine grass develops thin, spindly turf.
So long as fertility and drainage are adequate, St. Augustine grass tolerates a wide range of soil types. St. Augustine grass grows satisfactorily at a pH range from 5.0 to 8.5, but develops a chlorotic appearance in highly alkaline soils (above pH 7.5). It does not tolerate compacted or waterlogged soil conditions. St. Augustine grass is highly tolerant of soil salinity, producing satisfactory growth at salt levels as high as 16 mmhos. Bermudagrass will tolerate only slightly higher salt levels.
St. Augustine grass is used primarily for lawns as it does not tolerant traffic as well as some other warm season species. It produces satisfactory turf at moderate levels of maintenance, effectively competes with weeds and other grasses and has only a few serious pests.
In moist, warm climates St. Augustine grass maintains a satisfactory turf cover with only occasional mowing. In drier climates (below 30 inches annual rainfall) it survives with supplemental irrigation. At higher maintenance levels, St. Augustine grass produces a thick, lush, dark green turf that is highly preferred by homeowners.
Varieties. Since St. Augustine grass has been propagated vegetatively for 200 years, only a few strains or varieties have evolved and none have been developed through grass breeding programs. The common strain, a fertile diploid with a white stigma color, is native to the Gulf-Caribbean-W. African region. This species may have crossed with another species of Stenotaphrum to produce the sterile triploid strain originally reported in S. Africa. This strain, distinguished from the common strain by its purple stigma color, has been found in Australia, New Zealand and in the Pacific Islands. It has been planted in Florida since the 1890's and in California since 1920.
Several selections from Florida were made available prior to 1960. Floratine, a purple stigma type, was released by the Florida Agricultural Experiment Station in 1959. Floratine was released for its somewhat finer texture and darker green color than the typical purple stigma type strain found in Florida prior to that time. It also retains its dark green color long into the fall and was reported to tolerate closer mowing than other St. Augustine grass selections.
Prior to Floratine, Bitter Blue was selected as an improvement over coarser textured types of St. Augustine grass used in Florida for lawns. Both of these selections, Floratine and Bitter Blue, are similar to the coarse textured triploid types reported in Florida prior to 1900.
Floratam St. Augustine grass was released by the Florida and Texas Agricultural Experiment Stations in 1972 as a SAD virus and chinch bug resistant selection. Like other Florida types, Floratam is a vigorous, coarse textured St. Augustine grass variety. Floratam has a purple stigma color and is sterile. Stolons of Floratam are large, purplish-red in color with internodes averaging 3 inches in length. Leaf blades are wider and longer than common St. Augustine grass. The morphological characteristics of Floratam are similar to those of Roselawn St. Augustine grass which is used as a pasture grass on muck soils in south Florida.
Floratam is not as cold tolerant as the common type found in Texas. Its use should be restricted to south Florida and the coastal zones of other southern states. Floratam also lacks the degree of shade tolerance that other St. Augustine grass varieties possess.
Seville St. Augustine grass was released by the O. M. Scott and Sons Company in 1980 as a SAD resistant and chinch bug tolerant variety. Seville is much finer textured than Floratam, but it too lacks the necessary cold tolerance to extend its area of adaptation beyond the southern boundaries of the Gulf Coast.
Raleigh St. Augustine grass was released by the North Carolina Experiment Station in 1980 as a cold tolerant, SAD resistant strain. Raleigh is finer textured than Floratam and develops a dense turf much like the Texas Common strain of St. Augustine grass. Raleigh is also more shade tolerant than Floratam. But, unlike Floratam, Raleigh is not resistant to lawn chinch bugs.
A strain of St. Augustine grass grown and produced commercially in Texas since 1920 is called Texas Common. Texas Common is typical of the white stigma type reported to be native to the Gulf-Caribbean-West African region. Texas Common was found to be a fertile diploid with 18 chromosomes. Seedling progeny from this white stigma type show wide variations in morphological characters. However, since the strain has been propagated vegetatively for over 100 years, only a few variations in the grass have been produced. Natural variants of the common strain are found throughout the state. It is assumed that these variants developed from seed produced by the common strains of St. Augustine grass.
Dwarf and variegated types of St. Augustine grass have also been selected from seed produced by Texas Common. However, these strains are more ornamental and novelty grasses than turfgrasses. One of the dwarf types (patented in the U.S. as Garretts 141) has been evaluated for its seed production potential. However, Garrets 141 and its progeny lacks the cold tolerance necessary to extend its area of adaptation beyond Southern Florida and South Texas in the United States.
Propagation. As long as St. Augustine grass has been cultivated, it has been propagated by vegetative means -- stolons, plugs or sod. Only recently has the seed production potential of St. Augustine grass been realized; but, as yet, significant use has not been made of that potential.
As reported by Long and Bashaw at Texas A&M in 1961 only a few strains of St. Augustine grass are fertile. The common strain of St. Augustine grass found in Texas is generally fertile; whereas, the strains used in Florida since before 1900 were found to be sterile.
St. Augustine grass is readily established from sod since the species is vigorous and spreads rapidly by creeping stolons. Sod plugs or stolons planted on 1 to 2 foot spacings can be expected to cover in one growing season. In commercial St. Augustine grass production 300 to 500 square yards (bushels) of sod are planted per acre. In small lawn plantings, 2 to 4 square inch sod plugs are planted on 1 to 2 foot spacings. St. Augustine grass can be successfully established from plugs anytime during the growing season if water is available.
Unlike bermudagrass, St. Augustine grass is not effectively propagated from stolons. St. Augustine grass stolons are much more prone to desiccation than bermudagrass. Also, bermudagrass roots much faster and has a faster growth rate than St. Augustine grass. As a result, St. Augustine grass is not successfully established by hydromulching or broadcasting stolons.
Some St. Augustine grass strains can be established from seed by planting at 1/3 to 1/2 pound of PLS per 1,000 square feet. The rate of establishment from seed planted at that rate would be about the same as for 2 inch sod plugs planted on 1 foot spacings. A seeded St. Augustine grass lawn should be kept moist for several weeks after planting to obtain a satisfactory stand of grass. Only after the seedlings have begun to spread can the grass tolerate dry conditions. St. Augustine grass should be seeded in late spring to early summer.
Fertilization during the establishment period (first three months after planting) is critical to developing a complete cover of St. Augustine grass. A starter fertilizer (one high in phosphorous) or a balanced, complete fertilizer should be applied at planting time. Subsequent applications of nitrogen at monthly intervals at a rate of 1 pound per 1,000 square feet will promote rapid spread of St. Augustine grass plugs. Weeds can be controlled preemerge with atrazine or post emerge with asulam (Asulox) and hormone-type herbicides (2,4-D, MCPP, dicamba).
Management. After establishment the success of St. Augustine grass as a lawn grass depends largely on management. Mowing, fertilization and supplemental watering are required to maintain a dense, green, weed-free turf of St. Augustine grass. In coastal areas where rainfall is adequate, St. Augustine grass will survive with little care. In inland areas, where rainfall is less dependable, close management of water is required to maintain a satisfactory lawn with St. Augustine grass.
The growth rate of St. Augustine grass is dependent on temperature, moisture availability and nutrient availability. Any one of these factors can limit the rate of growth of this species. In the spring with mild daytime temperatures and cool night temperatures, St. Augustine grass greens up, but makes little growth. As day and night temperatures increase during late spring and summer, the growth rate increases. Thus, an established turf of St. Augustine grass may require mowing every 2 weeks in early spring and as often as every five days by late spring if nitrogen fertilizer is applied.
During the fall, as temperatures cool, St. Augustine grass maintains its dark green color, but its growth rate declines sharply. Mowing frequency may be reduced to twice monthly during late fall and early winter.
Mowing heights may range from 1 to 3 inches depending on the frequency of mowing and the degree of shade present. At mowing heights below two inches, St. Augustine grass should be mowed every five days during late spring and summer. At a 2° inch mowing height, a 7-10 mowing schedule is adequate. Above 2° inches, St. Augustine grass should be mowed at 10 to 14 day intervals. In moderate to dense shade, St. Augustine grass should be mowed at about 3 inches at 10 day intervals.
During the fall, mowing height should be raised about ° inch to increase total leaf area of the turf. The increased leaf area will help the grass accumulate energy reserves to get through the winter. The greater leaf area will also help prevent weed invasion during the dormant season.
St. Augustine grass is responsive to nitrogen fertilizer in terms of color and growth rate. On sandy soils St. Augustine grass requires about 1 pound of nitrogen per 1,000 square feet per month during the growing season to maintain satisfactory color and density. At rates above 1 pound per 1,000 square feet, St. Augustine grass produces lush growth that is highly susceptible to insects and diseases. On heavier textured soils ° pound of nitrogen every month is adequate to maintain good color and growth. Thatch accumulation is also a problem when nitrogen fertilization exceeds the required rate.
Late fall fertilization of St. Augustine grass helps maintain color and density of the lawn into the winter and promotes early recovery of the grass in the spring. Thus, to extend the length of time a St. Augustine lawn is attractive, the lawn should receive about 1 pound of nitrogen every 30 to 60 days from early spring through late fall.
St. Augustine grass is sensitive to iron deficiency and readily develops chlorotic symptoms in alkaline or iron deficient soils. This deficiency can be corrected with foliar applications or iron sulfate or iron chelate. Soil applications of iron sources are less effective than foliar application in alkaline soils.
Potassium requirements for St. Augustine grass are about the same as for other grasses. About half as much potassium as nitrogen is required to maintain growth. Potassium has been shown to increase root growth, cold tolerance and drought tolerance in St. Augustine grass.
Phosphorous requirements for established St. Augustine grass are very low and generally met from the soil. Occasional applications of a phosphorous fertilizer material may be required. Newly planted St. Augustine grass will respond to phosphorous fertilizers in terms of an increased rate of spread.[ More about fertilization ]
Insects. Several insect pests cause serious damage to St. Augustine grass lawns. The Southern lawn chinch bug is the most serious pest on St. Augustine grass in Florida where the insect if active most of the year. In other states it ranks among the most serious pests along with SAD, brownpatch and white grub.
The chinch bug damages St. Augustine grass by feeding on the stems at the base of the leaf sheath. Populations of chinch bugs may reach several hundred per square foot with damage usually apparent at 20 to 30 chinch bugs per square foot. Initial injury symptoms from chinch bugs resembles drought stress -- stunted, chlorotic spots in open (full sun) areas of the lawn. As feeding continues, irregular areas of dead grass develop in the lawn.
Timely applications of insecticides will control chinch bugs. Two or more treatments are required during the growing season in most areas, and as many as 5 or 6 may be required in some areas of Florida. Floratam St. Augustine grass is resistant to the Southern lawn chinch bug and is widely used in South Texas where the grass is adapted. In Florida severe damage to Floratam has been observed in lawns infested with chinch bugs.
White grub are also a serious pest on St. Augustine grass lawns. The grubs are the larvae of the May beetle or June bug that develop in the summer and fall just below the soil surface. The grubs feed on roots of St. Augustine grass and cause significant losses of turf during some years. Damage usually appears the following year as dead areas of grass that can be easily lifted from the lawn.
Grub control is difficult since the larvae are often quite large when detected and feed below the soil surface. Also, for them to be effective, insecticides must be drenched into the soil where the insects feed. Since some insecticides are tightly bound to the thatch layer of St. Augustine grass, drenching the material into the soil is difficult.
Timely and proper application of insecticides is the only method of controlling white grubs. Since they are only an occasional problem, inspection of the turf in midsummer is required for effective control. Biological control with milky spore disease has not been effective against this species of white grub.
Sod webworms, armyworms and cutworms can also feed on St. Augustine grass leaves and can cause damage when infestations are heavy. Evidence of heavy feeding by these insects includes a skeletonized appearance of leaf blade, silk-like webs visible in early morning (webs cover earthen tunnel in the thatch layer of turf) or defoliation of lawn in irregular patches. All of the leaf-feeding insects can be easily controlled by insecticides or biological worm control. (Bacillus sp.)
Ground pearls, subterranean scale insects that feed on roots of grasses, can also cause damage to St. Augustine grass lawns. The scale insects attach themselves to grass roots and secrete a waxlike shell around their bodies that resembles a pearl. At the immature scale inside the pearl grows larger, the pearl also increases in size. The pearl may reach 1/8 inch in diameter, and can be found attached to grass roots in the top several inches of soil.
Ground pearl damage becomes evident in spring and summer, particularly during dry periods, as small irregular areas of unthrifty or dead grass. Insecticide treatment should be made in May or early June when the insect is in the crawler stage. Consecutive treatments for 2 or more years may be required for effective control.
Diseases. St. Augustine grass is susceptible to a number of turfgrass diseases including brownpatch, SAD, gray leaf spot, Helminthosporium, Pythium, rust, downy mildew and others. All of these diseases, except SAD, are caused by fungi and can be controlled by good management and fungicides. SAD is a virus disease for which there is no chemical control. Only resistant varieties of St. Augustine grass are effective against this disease. Floratam, Seville, Raleigh and several experimental varieties have shown good resistance to the SAD virus.
Brownpatch and gray leaf spot are the most serious diseases caused by fungi attacking St. Augustine grass. Although these diseases rarely kill St. Augustine, they severely weaken and thin the grass to the degree that the lawn is unsightly. Preventive applications of fungicides are most effective against these diseases.
Weeds. A healthy St. Augustine grass lawn effectively crowds out most weeds. But St. Augustine grass that is not properly maintained or is weakened by insects or disease can be invaded by grassy and broadleaved weeds. Cool season weeds such as henbit, chickweed and clover are a serious problem in dormant St. Augustine grass. These weeds can be controlled by hormone-type herbicides in early spring.
Annual grassy weeds such as fescue, annual bluegrass and crabgrass are best controlled by timely applications of preemergence herbicides. Perennial grasses such as dallisgrass and bermudagrass are difficult to control in St. Augustine grass turf. Nonselective products can be applied as directed sprays to these weeds to obtain control.
Managing White Grubs
Knowing when you have a problem.
White grub damage can be detected by the presence of irregular-shaped areas of weakened or dying grass in the lawn. Less-severely damaged turf lacks vigor and is more vulnerable to invasion by weeds. Depending on location within the state, damage may appear anytime between the months of June and October. Turfgrass damaged by white grubs has a reduced root system and is easily pulled from the soil. Grubs should be readily found in the top few inches of soil, in the turfgrass root zone. Turfgrass usually recovers from white grub damage by fall or the following spring.
At least one turfgrass disease, Take-all Patch, can sometimes be mistaken for white grub damage. Take-all Patch occurs most frequently in spring and early summer, and can be distinguished by the rotted appearance of the roots. In contrast to white grub damage, dead spots caused by Take-all Patch may persist into the summer months.
Most Texas lawns probably do not experience damaging numbers of white grubs in any given year. For this reason, lawns should be inspected for grubs before a decision is made to treat. The best time to inspect for grubs is when they are small (1/2 inch or less). By detecting white grubs early, treatments can be applied before serious root damage occurs. Also, controls are more effective when applied to smaller larvae.
Several sites in the lawn should be examined to find out if treatment is needed. Soil sections at least 3 to 4 inches across and 4 inches deep (deeper samples may be advisable in sandy soils) should be examined for grubs. A good rule of thumb is to examine several soil plugs (up to one square foot per 1,000 square feet of turf) from widely scattered parts of the lawn, being careful to include areas of suspected grub damage. Treatment is justified when more than five white grubs per square foot are found, although some lawns may be able to sustain higher numbers without noticeable damage.
When to Treat.
The best time to inspect for grubs and apply insecticides occurs approximately five to six weeks after the heaviest June beetle flights. Peak June beetles flights occur at different times of the year in different parts of the state. Within a given locale, flight periods may vary as much as two months from year to year, due to variations in rainfall.
In some areas, May or June beetle species that do not attack turf may become abundant at lights and cause confusion about when to treat. For this reason, it's best to consult with your local county Extension office to confirm the optimal treatment period for your area. Generalized guidelines for the best inspection and treatment times for major metropolitan areas in Texas are summarized in Figure 4.
Figure 4. Optimal treatment times for white grubs in Texas.
Non-chemical controls.
Several non-chemical treatments are available for controlling white grubs. Beneficial nematodes within the genera Steinernema and Heterorhabditis are tiny worms that attack white grubs and other soil inhabiting insects. These microscopic worms can be purchased in stores or through garden supply catalogs. Commercial nematode products are usually designed to be mixed with water and applied to lawns using a hose-end or hand-held sprayer. Recent research shows that under good conditions, commercially- available nematodes can reduce white grub populations by up to 50 percent.
Nematodes must be supplied with adequate soil moisture to help them move down into the soils where grubs are feeding. At least 1/4 inch of water should be applied before, and another 1/4 inch of water applied just after, nematodes are sprayed on the lawn. These worms pose no threat to humans or landscape plants, and are an environmentally sound alternative for those who prefer not to use pesticides on their lawn.
One microbial pesticide, Bacillus popilliae, or milky spore disease, often is recommended for white grub (Japanese beetle) control in other regions of the U.S.; however, it has not been shown to be effective against Texas turf-infesting white grubs.
Spiked sandals sold for aerating turf have been tried with some success for controlling damaging grub populations. According to one study, repeatedly walking over heavily infested turf with the spike sandals may reduce grub populations up to 50 percent. These sandals are available through several garden supply catalogs.
Chemical control.
Proper timing of insecticide treatments is one of the most critical elements for successful suppression of white grubs. Both chemical and biological control measures are most effective when applied against smaller (less than 1/2 inch long) larvae, and less effective against eggs, larger larvae, and pupae. The residual effectiveness of most insecticides is greatly reduced one to two weeks after application; thus, insecticides applied too early may not remain effective in the soil through the egg hatch period. Insecticides applied after the optimal treatment period are often less effective because white grubs have become large and difficult to kill.
If grubs are restricted to certain areas of a yard, treat the infested areas only.
Effective white grub insecticides for use by consumers include chlorpyrifos (Dursban®), diazinon, imidacloprid (Merit®) and isofenphos (Oftanol®). A decline in white grub numbers should be observed within 2 or 3 weeks after treatment. Properly timed and applied chemical treatments should be effective with only one application. When using imidacloprid, applications should be made before damage becomes evident, as this product is most effective against first- and second-instar larvae.
Irrigating the soil prior to insecticide application, particularly when the soils are dry, can improve the effectiveness of insecticides. For dry soils, apply 1/4 to 1/2 inch of water the day before a treatment to improve spray penetration of the soil and to encourage white grubs to move closer to the soil surface. This makes grubs easier to contact with the insecticide treatment.
Post-treatment irrigation is essential. Liquid insecticide formulations must be watered in with 1/2 to 1 inch of water immediately after application to ensure that insecticides reach the root zone. Granular formulations should be irrigated within 24 hours to wash the insecticide into the soil and reduce the chance for the insecticide to be picked up by birds or other wildlife. A rain gauge or straight-sided can should be used to verify that sufficient irrigation water has been applied. Two or more waterings may be needed to apply sufficient water if the soil is wet or difficult to penetrate. If water is applied too quickly, runoff and loss of pesticide may occur.
Heavy thatch buildup can reduce the effectiveness of insecticide sprays. Thatch is the accumulation of dead plant material, such as dead grass stems, between the soil surface and the turfgrass foliage. Thatch layers greater than 1/2 inch can result in greater susceptibility of the turf to plant diseases and can lead to other problems. Recent research has shown that many pesticides bind to thatch, preventing them from reaching the soil, and reducing their effectiveness. Dethatching machines or soil aerifiers (that remove small plugs of soil) can be rented to help remove thatch and enhance penetration of the turf by pesticides. Excessive thatch buildup is more likely to occur with hybrid bermudagrasses, St. Augustinegrass and some zoysiagrasses. Use of mulching mowers to recycle grass clippings should not cause thatch buildup in regularly mowed lawns.
Environmental considerations.
Unnecessary insecticide applications sometimes create more problems than they solve. Pesticides can have detrimental effects on beneficial organisms, like earthworms, that help decompose thatch. Most insecticides do not discriminate between "good" and "bad" bugs and may kill beneficial insects that help control other pests. Also, unnecessary pesticide applications can increase the risk of insecticide resistance developing among white grub and other pest populations. For these reasons, routine, "preventative" insecticide applications to lawns for white grub control are not recommended.
Heavy rainfall can wash recently applied pesticides out of lawns, especially if the ground is saturated with water when the treatment is applied. Avoid treating lawns just before a heavy rain is expected. Also try to avoid application of pesticides to street gutters and sidewalks. Drop-type spreaders are less likely to scatter pesticide granules off the target site than are rotary-type spreaders. (Figure 5). Pesticide runoff from improper pesticide applications reduces the effectiveness of a treatment and can pollute above-ground and underground water supplies.
One should be aware that certain insecticides can be highly toxic to birds and other wildlife. Always read and follow label directions, including the precautionary statements pertaining to potential environmental hazards. Apply only the labeled rates, avoid pesticide use near streams and ponds, and irrigate treatments promptly to help reduce the risk to non-target organisms like birds. Diazinon is especially toxic to birds and has been a problem contaminant in many community wastewater and stormwater effluents. Particular care should be taken when using this product where songbirds or other birds are abundant or where contamination of surface water may occur. Never dispose of leftover diazinon or any other pesticide down sewer or stormwater drains. Such actions can cause toxicity to fish and other aquatic organisms.
For more information on pests, pest control, and pesticide products, please see Extension publication, B-1373, House and Landscape Pests.
http://harris-tx.tamu.edu/IPM/OtherInsects/managingwhitegrubs.html
Core Aeration
It's entirely possible that the grass will be unable to take up the nutrients provided by spring fertilization due to poor soil conditions. Is the soil beneath your grass hard and lumpy? Does water run off after the grass has been irrigated? Does it always seem "thirsty", i.e. wilts by the next summer's day? Is it not as green as it should be? If so, then your lawn is a prime candidate for core aeration.
Core aeration is a performed with a special machine that pulls out plugs of soil. This opens up the soil structure, allowing air, water and fertilizer nutrients to penetrate more deeply reaching the grass roots. Core aeration makes the soil more friable, "crumbly", a condition allowing roots to grow down rather than up. When roots are growing up this is thatch. Friable soil also helps earthworms, nature's core aerators, to better able tunnel through the lawn, moving more nutrients and water. Plus the casings they leave behind are excellent fertilizers.
Mid-March through April is a good time to do this as the soil is usually softer from our spring rains, making it easier to core aerate. Whether you perform the core aeration, or hire a company for the job, make sure the machine being used has the appropriate length tines and spacing. Soil scientists and turfgrass experts recommend tines are a minimum of 4-inches in length, with a spacing of 2- to 3-inches. If the tines on the machine are farther apart, it will need to go over the same area multiple times.
First, make sure to mark off sprinkler heads -- you don't want to run the machine over them. Not only will that damage them, it will also damage the machine's tines making it useless. Core aerate the lawn. The cores then can be either left to degrade naturally, or be broken up a day or two afterwards by simply mowing over them. Apply an organic lawn fertilizer at 2 - 3 times the recommended rate. The reason for choosing an organic fertilizer is that compacted soils are not only nutrient poor, they structurally weak, which is why they became compacted in the first place. Organic fertilizers contain materials that help build up soil structure. Because organic fertilizers have high amounts of insoluble nitrogen, this amount will last longer, allowing you to skip that midsummer feeding in July if you so choose. Once this has been done, water the lawn thoroughly to help move both the soil and fertilizer into the holes. The holes will eventually fill in, completely disappearing within month.
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