Turf Grass Research

By Gerald Henry, Ph.D., Assistant Professor, Turfgrass Science, Texas Tech University

The photo shows nine new cultivars that came from the initial breeding work done at Texas Tech with centipedegrass. All of the plants were grown in a soil with a pH of 8.2. The picture was taken three months after germination. The plants that are green are responding favorably to the high soil pH, while the yellow plants are not tolerant to the high soil pH. The green plants will be entered into the centipedegrass breeding program for creation of new cultivars.

The Turfgrass Science program at Texas Tech University in Lubbock, Texas dedicates itself to providing local and statewide support for golf course, athletic field, and home lawn turf management.

Its research focuses on identifying and breeding improved turfgrass varieties, enhancing turfgrass establishment, and developing best management practices for key turfgrass pests. Several years are invested into the identification, collection, and evaluation of turfgrass germplasm through traditional breeding methods.

Centipedegrass

Centipedegrass is a warm-season grass commonly used for home lawns and roadsides throughout the southeastern U.S. from Virginia to Florida and west to Texas. It typically requires less mowing, nitrogen, irrigation, and pest management practices compared to other warm-season turfgrass species.

Limitations to the widespread use of centipedegrass include low tolerance to high soil pH and cold temperatures. Collaborative research with the University of Georgia and Dr. Brian Schwartz over the past few years has been dedicated to the genetic improvement of centipedegrass through the evaluation of seed collected in central and southern China in the fall of 1999. Several new varieties adapted to high soil pH and low temperatures have been identified and are currently entered into the breeding efforts to create improved centipede-grass cultivars. Once these new cultivars are back-crossed with older cultivars that contain desirable traits, they will eventually be given a name. It can take another five years before some of these new cultivars become commercially available.

Heat, Drought and Salt-Tolerant Tall Fescue

Collaborative research with Rutgers University and Dr. Bill Meyer over the past four years has focused on the identification of tall fescue varieties that are heat, drought, and salt tolerant. Most of these experimental lines also exhibit rhizomatous growth, which aids in recovery from wear/stress and reduces the need for annual reseeding to maintain a dense stand of turf.

Research plots subjected to three consecutive months of drought this past summer yielded several new tall fescue varieties that will be entered into the breeding program at Rutgers University in the years to come. Similar to the centipedegrass work, these cultivars are also denoted as experimental lines. It can take another five years before some of these new cultivars become commercially available.

Cores of bermudagrass were removed from research plots to test products to enhance establishment. The two cores on the left were removed from plots treated with a typical starter fertilizer (5-5-5), while the two plugs on the right were removed from plots treated with a typical starter fertilizer (5-5-5) + humic/fulvic acid + calcium lignosulfonate. The two plugs on the right had a 30-percent increase in rooting mass three months after seeding.

Enhanced Turfgrass Establishment

Choosing the proper turfgrass variety is only the first step in creating a healthy stand of turf. Seedlings and immature plants are often more susceptible to environmental stresses since they don't have extensive root systems and can't easily obtain water and nutrients. Reseach indicates that amending the soil with products containing extracted humic/fulvic acid, calcium lignosulfonate, seaweed extracts, and microbial inoculants may enhance seed germination, improve nutrient absorption, and increase root penetration. Research at Texas Tech University with humic/fulvic acid and calcium lignosulfonate yielded a 30-percent increase in rooting mass of bermudagrass grown from seed and plugs during the first few weeks of establishment.

Seaweed Extracts

In other research, combining traditional starter fertilizers with seaweed extracts increased turf roots 23 to 37 percent compared to fertilizer alone after four months of growth. Tierra Resources International, Inc. offers the commercial products that contain humic/fulvic acid. The commercial products that contain calcium lignosulfonate came from Tierra Resources International, Inc. The commercial products that contain seaweed extracts came from Sustane Natural Products.

More than a dozen different species of white grubs damage turf in the southern U.S. Most grubs feed primarily on grass roots, causing a reduction in water and nutrient uptake by plants.

White Grubs

A shift in white grub species is occurring in many areas where masked chafers (Cyclocephala spp.) overlap with Japanese beetles. For reasons not fully understood, urban neighborhoods that previously hosted 80-100 percent Japanese beetle populations are now predominately populated with masked chafers. Selective natural control with milky spore disease and other beneficial pathogens may be part of the explanation for the shift.

Masked chafers are not affected by milky spore disease. Several chemical control options exist for the control of white grubs in turfgrass, however, most of these insecticides provide inconsistent control of masked chafer grubs. Field experiments were conducted at the Texas Tech Turfgrass Research Farm in Lubbock to examine the effect of several insecticides for the control of masked chafer grubs.

Treatments were sprayed in mid-May and consisted of chlorantraniliprole (Acelepyrn) (8 or 16 fl oz/A), halofenozide (Mach 2) (4 qt/A), imidacloprid (Merit) (8.6 oz/A), and clothianidin (Arena) (6.4 or 12.8 oz/A).

Chlorantraniliprole treatments exhibited 100-percent control regardless of application rate 20 weeks after treatment. Control with halofenozide and imidacloprid treatments ranged from 88-to-91 percent. Clothianidin at 6.4 oz/A exhibited 88 percent control, while the higher rate (12.8 oz/A) provided complete control.

The squares that are showing up in the picture illustrate the high level of control of dallisgrass in response to applications of Celsius plus Revolver (foramsulfuron.)

A research trial at the Quaker Research Farm at Texas Tech University examinines the establishment of buffalograss and bermudagrass from seed with different mulching media (no mulch, wheat straw, gin trash, or hydro-mulch).

Dallisgrass: A Troublesome Weed

In 2004, the Southern Weed Science Society survey named dallisgrass as one of the 10 most troublesome turfgrass weeds in 10 of 11 states in the southern U.S.

Dallisgrass is a rhizomatous perennial warm-season grass that has long been used as a forage or roadside grass, but its ability to adapt to a wide range of environmental factors may have led to its success and spread as a turfgrass weed. Until recently, chemical control of dallisgrass was neither efficient, nor cost effective. Typical programs included multiple applications of monosodium methanearsonate (MSMA), which can be damaging to warm-season turfgrasses, or applications of glyphosate, which can be even more harmful to desirable turfgrass species.

Experiments were conducted at Meadowbrook Country Club in Lubbock for the post-emergence control of dalliesgrass in bermudagrass turf. Treatments consisted of combinations of dicamba + iodosulfuron + thiencarbazone (Celsius) (0.08 oz/1000 ft2) and foramsulfuron (Revolver) (0.4 fl oz/1000 ft2) applied in late August or early September. A sequential application was made following dallisgrass re-growth approximately 4-to-5 weeks later. Dallisgrass emergence the following spring was severely reduced (< 5% regrowth) with no bermudagrass damage.

Spring dead spot (SDS) is considered to be the most devastating disease to infect bermudagrass turf throughout the transition zone and southern U.S. where temperatures drop low enough during the winter to induce dormancy.

Spring Dead Spot

Efficacy of fungicides for the control of SDS and other root-infecting fungi may be limited by fungicide penetration into the soil profile. Therefore, cultivation practices aimed at reducing the thatch layer may also increase fungicide infiltration. Experiments were conducted over the past few years at Hillcrest Country Club in Lubbock, Texas to evaluate the effect of cultural practices on fungicide efficacy for the control of SDS disease in bermudagrass.

Cultural treatments were conducted prior to fungicide application and consisted of no cultivation, verticutting, hollow-tine aerification, or aerification + verticutting. Fungicide treatments were applied in mid-August and consisted of fenarimol (Rubigan) at 6 fl oz/1000 ft2 or tebuconazole (Torque) at 0.6 fl oz/1000 ft2. Sequential applications were made 30 days after initial treatment.

Verticutting did not increase the efficacy of either fungicide. Aerification and aerification + verticutting in combination with fenarimol (Rubigan) and tebuconazole (Torque) reduced SDS pressure 44-to-50 percent and 80-to-87 percent, respectively, compared to the application of fungicides alone.

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