1. Turfgrass Pest Management (Category 3A)

    2. Care of Turfgrass

    Chapter 2

  2. Most people realize the importance of turf as ground cover, and for erosion control. Few understand the ecological benefits of a healthy, vigorous stand of grass.
  3. Like all plants, grass releases the oxygen we breathe. The extensive fibrous root system of turf holds soil in place, and adds organic material. Pollutants, dust, and other particles in snow and rain are filtered by grass plants reducing leaching into the groundwater. Finally, turf stands are one of the most efficient biological systems for breaking down pesticides. These features clearly make healthy turfgrass more than purely an aesthetic concern.
  4. Non-pest disorders as well as pests injure turf. In fact, most turfgrass injury is due to poor growing conditions that occur naturally or are created by maintenance practices. Environmental and cultural disorders include:
  1. -Soil copaction

    2. -Competition with the roots of other plants.

    -Excessive wear or traffic.

    -Too much thatch

  2. - Improper height of cut.

Note: when non-pest disorders are not a problem for turf, rarely are pests damaging.

  1. Many types of organisms are pests of turfgrass:

To best manage pests, be aware that pest problems are often a result, rather than the cause of, poor quality turf.
  1. For turf to grow well, correct amounts of water, nutrients, and sunlight are needed. When one or more climatic or soil conditions do not fall within acceptable ranges, turfgrass becomes stressed. Weakened turf may thin and be easily invaded by weeds. Stressed grass plants are less able to combat and recover from insect or disease injury
  2. The greatest influence on turf health and quality is water. Grass plants need water to grow and maintain tissues, and to cool themselves through transpiration. When water is limited, turf growth stops, transpiration decreases, and grass plants heat up. Eventually water-stressed turf browns-out and goes dormant.
  3. As with all types of plants, turfgrass species are adapted to certain climatic regions. The condition that most limits where grasses are found is their tolerance for cold temperatures.

    4. Cool season grasses: Kentucky bluegrass; perennial ryegrass; fine fescues; tall

    fescue; bentgrass

    Transition grasses: tall fescue; zoysiagrss; bermudagrass

    Warm season grasses: zoysiagrass; bermudagrass; St. Augustine grass;

    Centepedegrass; bahiagrass.

  4. The northern third of the United States, including Michigan, is a cool/cold grass adaptation zone. Shoot qrowth is greatest in cool-season grasses when temperatures are between 60-75˚ F. Maximum root growth occurs when soil temperatures ranges between 50-65˚F. Cool-season grasses brown-out, but survive the winter and hoe periods in a dormant condition.

12. When temperatures are beyond the optimal of 50-75˚F, the entire grass plant is affected. Respiration ― the use of oxygen during the processes of growth and maintenance ― increases with temperature. Conversely the process of making food, photsynthesis, declines with high temperature. Increased plant activity with decreased food production creates a shortage of energy in the plant. Limited energy then is available to produce roots and shoots, maintain tissues and fight pests.

  1. All plants require sunlight for photosynthesis, but preference in the amount of sunlight differs with plant species. In generl, grasses do best when grown on sunny and partially-sunny sites.
  2. Turf grown without adequate light is shallow-rooted, thin, and more prone to diseases. In fact, shade itself is sometimes considered a turf disorder.
  3. Soil type influences the level of moisture, air, and nutrients available to grass plant roots. While soil requires many years to develop, it is easily destroyed by disturbances such as construction grading.
  4. Soil is comoposed of inorganic particles (minerals) and organic matter (remains of organisms), water, air, and soil organisms.
  5. An ideal soil contains 50% organic and inorganic solid particles, and 50% open space (pores). Soil pores are filled with water and air. The percentage of pores occpied by water depends upon soil type, drainage pattern, and time of the year.
  6. The inorganic part of soil is made up of sand, silt, and clay particles. Soil texture is defined by the percentage of large, medium and small particles making up the soil.
  7. Sand is relatively large-sized mineral particles. When packed together sand particles typically resist compaction and may large pores are created. Because large-sized particles hold a limited amount of water and nutrients, sandy soils are relatively unfertile, but drain well.
  8. Clay particles have the greatest ability to hole nutrients and water, but compact tightly together. Clay soils are known for their density and "wetness," and lack of air-filled pores. While nutrients will not readily leach out of clay soils, they may be held too tightly to be absorbed by roots.
  9. An ideal soil, which has good nutrient and water-holding capacity as well as plenty of air-filled pores, is composed of all sized particles.
  10. Soil pH is a measure of soil acidity. Most turfgrass grows adequately in soil with a pH from 5.0 to 7.5.
  11. Soil pH greatly affects the availability of nutrients to plants. Plants grown in soil with a pH far from the 6.0-7.0 range can be deficient in certain nutrients. Phosphorus and iron are elements the will form insoluble compounds that roots cannot absorb. Add lime to raise soil pH, and sulfur to lower pH. As with all soil adjustments, never alter soil pH without first testing the soil.
  12. The percentage of clay particles and organic matter determines the nutrient-holding capacity of soil. Nutrients in a soil are in constant flux, becoming more or less available as soil conditions change. You must understand the function of the 16 nutrients and determine which needs to be supplemented for each turf stand .
  13. Remember, even when you suspect that injured turf is showing symptoms of nutrient deficiency, soil analysis is the only way to be certain.
  14. There are three primary nutrients required by plants in relatively large amounts: nitrogen (N), phosphorus (P or P2O5) and potassium (K or K2O). Micronutrients, such as iron and sulfur, are elements used by plants in relatively small amounts.
  15. Compared to other nutrients nitrogen is used in the largest quantity by turf. Dry turf clippings are about 5% nitrogen by weight. Turf deficient in nitrogen may have poor color, decreased elasticity, and is less able to compete with weeds. Nitrogen is oftern unavailable to turf roots because it leaches through the soil rapidly and is used by soil organisms, or simply has not been supplied. It is no surprise that turfgrass responds more to nitrogen applications that any other element.
  16. Periodic applications of nitrogen fertilizer are necessary to maintain good quality turf. However, too much nitrogen results in a thin root system relative to top growth, increased disease, and reduced drought and wear tolerance. Also, nitrogen fertilizer can contaminate surface and ground waters. Do not over-apply nitrogen. Do not exceed a rate of one pound of actual nitrogen per 1,000 square feet in a single application.
  17. Phosphorus is important for root development, maturation, and seed production. Since it is practically immobile in soil, few soils are deficient in phosphorus. Turf deficient in phosphorus shows purpling of grass blades. This symptom can be confused with the color change caused by cold weather.
  18. Phosphorus is strongly absorbed to soil particles and so can be carried into surface waters with eroding soil. Except for newly-established turf stands, phosphorous applications should be limited without evidence of deficiency. A soil test of 50 pounds of phosphorus per acre is adequate for turf growth.
  19. Turf uses potassium in quantities second only to nitrogen. This element is important for rooting, and wear and climatic stress tolerance. Turf deficient in potassium has yellowing and dead blade tips. These symptoms are rarely obvious, however. Even though the level of potassium in a soil is high, it may not be available for absorption by turf root. Therefore, routine application of potassium fertilizer at a ratio of 3:2 (3 parts nitrogen to 2 parts potassium) is beneficial in many situations. Potassium application will not result in dramatic growth. Do not interpret lack of green-up as a lack of benefit.
  20. Micronutrients are elements used by turf in relatively small amounts. They include manganese, boron, copper, and zinc. Typically, micronutrients required by turf are naturally present in Michigan soils in adequate amounts. High soil pH can "bind up" micronutrients so that they are unavailable to roots. Iron is a micronutrient commonly deficient in plants growing in alkaline soils (pH greater than 7.0). Iron-deficient grass blades have blotchy yellow patches, or are white. Application of iron fertilizer provides temporary green-up of turf. Since the deficiency is due to soil alkalinity, long-term treatment requires modifying the soil pH.
  21. One teaspoon of soil can contain a billion bacteria, a million fungi, and several thousand algae. Fortunately, most of these organisms improve soil conditions for plants growth. As they feed, soil organisms break sown organic matter and release nutrients. Pesticides can also be broken down by soil organisms. Burrowing creatures aerate the soil and increase drainage.
  22. Turf managers often battle disorders that are a resuld of poorly-established turf. Prevent chronic turf problems by carefully selecting and installing turfgrass.
  23. There are dozens of varieties of Kentucky bluegrass, perennial ryegrass and fine fescue commercially available for planting in Michigan. It is crucial to select grass species or varieties best suited to the growing conditions and planned used of the site.
  24. Grass species and varieties differ in their apperarance, wear tolerance, and maintenance requirements. They also differ in their susceptibility to damaging pests and tolerance of poor growing conditions. No turfgrass variety will meet all of your needs, so carefully consider which turf features are most important for each site.
  25. Turf stands made up of several grass types have greater genetic variation, and so better resist pests and adapt to different growing conditions.
  26. For this reason, grass seed is commonly marketed as blends of varieties or mixes of grass species. For instance, blends or mixes may contain a shade tolerance grass that will take over where the dominant grass dies out. Species mixtures are more adaptable, but are not as uniform, as blends.
  27. Consider using seed of fescue and ryegrass varieties containing fungi endophytes. These are naturally-occurring fungi that are harmless to grass plants, but repel or kill chewing insects. Make use of this natural control whenever possible, but be aware that endophyte fungi can be harmful if eaten by livestock.
  28. Avoid or reduce future turf problems by following proper planting procedures. Preparing a site for a new turf stand requires planning, materials, and labor:
  1. - Plow, rototill, disc, or otherwise work the soil to a depth of at least 6 inches.
  1. Be certain to properly care for newly-planted grass. Even the best planting materials and procedures will not succeed will not succeed without post-planting care.
  2. The amount and frequency of watering depends upon weather conditions. Check new turf regularly so that adjustments in watering can be made before turf becomes stressed. Keep new strands moist but not wet. Decrease the frequency and amounts of irrigation as seedlings begin to develop.
  3. Mow as soon as new turf grows past the desired height. Always keep mower blades sharp and properly adjusted to make clean cuts. Dull blades may pull up seedlings, or make ragged cuts which slows healing and may encourage disease infection.
  4. New stands benefit from fertilization a couple of weeks after seedlings emerge or new roots develop. Nitrogen fertilizer should be applied at a low rate (1/2 pound N per 1,000 square feet). Include potassium since it is particularly beneficial to establishing turf plants. To avoid burning soft, new grass plants, water fertilizer in immediately after application.
  5. Weeds are likely to invade establishing turf stands, but new grass plants are tender and have sparse root systems. Avoid exposing young grass plants to herbicides or other pesticides. Use other methods like pulling weeds and mowing until the turf is well-established. If pesticides must be used, check the label for use on newly-established turf.
  6. Maintaining turf is often the greatest landscape cost. Surprisingly little time and forethought is given to this task. Depending upon species, use and landscape importance,turfgrass requires:

48.When developing a turf management program, remember there is no benefit to managing turf at a level of visual or wear quality above that required for its use. Neither the aesthetic value nor utility of roadside grasses would be improved through intensive mowing, fertilizing, or irrigation.
  1. During dry periods there may not be enough rainfall to maintain actively growing turf. Supplying the right amount of water is not simple. Research shows that an average of 40% of irrigated water exceeds turf needs. Too much water is just as damaging to turf as is drought. So, how much water should be applied to turf? Ther are no simple answers. Learn the turfs water requirements and consider site conditions.
  2. The amount of water used by turf is measured as evapotranspiration—water lost by evaporation plus the water used in transpiration. When the amount of water lost due to evapotransiration is greater than the amount turf roots absorb, wilt and stress occurs.
  3. In general, turf requires a total of one inch of water per week from rainfall, irrigation or both. Most sources recommend applying water once a week during the early morning hours. But, researchers found this irrigation method can increase disease or cause turf to dry out and become stressed. During hot, droughty periods turf may better benefit from daily, light (1/5-2/5") afternoon waterings Since this practice will not deliver a full inch of water per week, regularly check the moisture of deeper soil and apply additional water when necessary.
  4. Obviously, turf cannot properly be watered using an automatic irrigation system set once during the growing season!
  5. Though mowing is one of the most costly maintenance procedures, it often becomes a routine practice that is not evaluated or adjusted. Good mowing practices at preferred heights of cut generates dense, uniform, vigorous turf. A general rule of thumb is to remove no more than one-third of the grass blade per mowing. Cutting turf too short may scalp the plants and damage the crowns, and reduce vigor. Thin or injured turf encourages weed and other pests. Conserve water in turf during hot,dry weather by raising the height of cut and mowing during cooler hours of the day.
  6. Grass clippings are routinely removed from low-cut, high-maintenance stands to improve appearance and texture. Clippings are also routinely removed from ‘ordinary’ grass stands with the misbelief that this practice prevents excessive thatch build-up. As clipping are removed. And, grass clippings should not be overlooked as a significant source of nutrients.
  7. One year’s worth of degrading clippings provide 4 pounds of nitrogen, 1 pound of phosphorus, and 2 pounds of potassium per 1,000 square feet. When clippings are removed, fertilization must be increased by 25-50%.
  8. Set a clear objective when planning to fertilize turf. Consider the species/variety’s nutrient preferences, and stresses affecting the turf. If the management goal is to promote growth, than nitrogen applications are warranted. Medium to high-quality turf requires fertilizing each season. However, roadside turf used for erosion control may require little or no fertilization.
  9. Many types of liquid and solid fertilizers are available for use on turf. Characteristics:

    10. Water-soluble. Nutrients are readily available to truf roots and provide a quick response.

    Slow release (slow-soluble) fertilizers release nutrients over time. They are more expensive, but fewer applications at higher rates are possible with less chance of burn.

    Synthetic fertilizers have compounds produced artificially by humans. They can be slow or quick release.

    Organic fertilizers: The nutrients are part of naturally-formed compounds and are released over time.

    Fertilizer analysis is the ration of actual nitrogen (N), phosphorus (as P2O5), and potassium ( as K2O) in complete fertilizer. A 21-4-8 fertilizer contains 21% nitrogen, 4% P2O5, and 8% K2O.

  10. Fertilizer burn usually occurs with high rates of soluble fertilizer, especially when applied to frozen ground, onto wet foliage, or during hot weather. Injury may be restricted to grass blades, but severe burn can damage roots and kill grass plants.
  11. To prevent turf injury when fertilizing:
  1. Compacted and heavy clay soils have less air and a hard surface that drains poorly. Lack of air, beneficial organisms and drainage all contribute to poor turf quality.
  2. Holes can be made in compacted soils with mechanical aerators. Aeration increases the movement of air in the soil and improves drainage. Machines that remove cores form the are generally more efficient aerators than those that spike or slit the soil.
  3. A layer of thatch exists in most turf stands between the green vegetation and the soil surface. Thatch is composed of tightly intermingled living and dead stems, leaves and roots. A thin thatch layer reduces soil compaction, moderates soil temperature, and reduces evaporation.
  4. Too much thatch, however, restricts water and air movement into the soil, and may encourage pests. High nitrogen fertilizer accelerates thatch production. Because soil organisms break down thatch, pesticide use may also contribute to thatch build-up.
  5. Practices that relieve soil compaction also help break down thatch. Vigorous hand-raking will remove thatch on small turf areas. Dethatching machines that cut out chunks of thatch are used on larger areas. Processing that debris back into the soil will improve turf quality and decrease thatch production.
  6. Turf grasses are sun-loving plants, and generally do best in full to partial sun. Some grasses are more tolerant of shade than others:

 

  1. In addition to not meeting the sunlight requirements of grass, there are two ways shade injures turf. Turf shaded by trees and shrubs often suffers from drought. Turf roots must compete with tree and shrub roots for water and nutrients. Also, the canopies of large plants catch moisture before it lands on the turf below. In contrast, turf shaded by buildings and hills remains too wet because of reduced wind and sun exposure. High humidity in these conditions favor turf diseases.

There are several ways to increase light intensity and air movement for the benefit of turfgrass: