Taking an environmentally sensitive approach to pest management


Missouri Environment & Garden



AUTHOR

Brad S. Fresenburg
University of Missouri
Division of Plant Sciences
(573) 884-8785
fresenburgb@missouri.edu

Home Lawn Basics

Brad S. Fresenburg
University of Missouri
(573) 884-8785
fresenburgb@missouri.edu

Published: March 1, 2009

We have just had a major thaw after several weeks of cold weather and a few days of warmer weather is encouraging tree buds to swell and perennial bulbs to send up shoots. These are the signs that get most home gardeners anxious to start spring chores, one of which is home lawn care. Rather than lay out a punch list of items to do for the spring, it would be more advantageous to cover home lawn basics that apply to the entire season. These basic practices will offer a more complete approach to lawn care that will build a healthy lawn that is more environmentally friendly to Missouri’s ground waters.

How to Soil Test:

A routine soil fertility test (pH, neutralizable acidity, phosphorus, potassium, calcium, magnesium, organic matter, and cation exchange capacity) is recommended under the following circumstances:

  • Before establishing a new lawn, whether from seed, sod, or sprigs.
  • Every three years on established lawns (early spring or early fall).
  • Annually when attempting to correct a nutrient deficiency or change the soil pH.

Taking a soil sample:

  • Your local MU Extension center has soil sample boxes available for use at no charge. One box (1.5 to 2 cups) is all the University lab needs for analyses.
  • Using a small shovel or soil probe, sample to a 4 inch depth on established lawns or before seeding.
  • Take 12 or more random cores from each area of the lawn to be tested and remove the thatch and live plant material before breaking up the cores and mixing thoroughly in a clean, dry plastic bucket. (Metal buckets contaminate the sample with micronutrients.) Take random samples from the lawn as a whole unless there is a need to sample problem areas separately.
  • Obtain a Horticulture Soil Sample Information form, MP 555, from your local MU Extension center or from the Web (http://www.soilplantlab.missouri.edu/soil/). For additional information refer to MU Guide G6954 – Soil Testing for Lawns. Send the sample to the Soil and Plant Testing Laboratory at the following addresses or your local Extension office:

    23 Mumford Hall
    University of Missouri
    Columbia, MO 65211

Measuring Your Lawn

Area measurements and mapping a lawn should be the first step in any home lawn care program. It is essential to know the square footage of your lawn in order to make accurate applications of fertilizers and other lawn care products. The most commonly used area measurements are square feet (sqft) and acres (ac). Most home lawns can be measured up in units of 1,000 sqft.

Calculating area can be accomplished using a simple method of dividing your lawn into geometric figures (rectangles, triangles, and circles). After taking several measurements, add each section for a total square footage. Another approach would involve taking a length and width measurement of your lot size, then subtract the square footage of your home, driveway, sidewalks, etc.

Geometric figures

  • Rectangle - Area = length x width
  • Triangle - Area = (length of base x height) /2
  • Circle - Area = 3.14(radius)2

Applying Products Correctly:

Proper applications of fertilizers and lawn care products are important to the health of your plants and quality of the environment. Applying too much of a synthetic fertilizer or pesticide to your lawn may cause foliar burns and injury or have negative environmental effects. While applying too much of a natural lawn care product is usually not injurious to your lawn, it can be economically infeasible. Applying too little of fertilizers or lawn care products can result in a low quality lawn, deficient in what it needs; making your lawn more prone to pest problems.

The only way to know just how much fertilizer or lawn care product is being applied to your lawn is to calibrate your application equipment. Calibrating simply begins with knowing the total square footage of your lawn and making sure you apply the correct amount of material for that square footage according to the manufacturer’s recommendation. Always read and follow the product label.

Calibrating spreaders:

Homeowners have a wide variety of spreaders to work with - some drop type, some rotary type, some listed on the product label for recommended settings, and many that are not. Rotary type spreaders are the best option in the application of lawn care products. They make applications easier, due to the fact that you do not need to worry about coming back precisely on your previous wheel marks. Rotary spreaders also require fewer passes to cover your lawn.

The best approach for homeowners does not necessarily involve the actual calibration of their spreader, but a more common sense approach to applying lawn care products. First, you need to accurately measure the square footage of your lawn and then purchase the correct amount of lawn care product. Second, evenly distribute that material over the total square footage. For example, you measured your lawn to be 10,000 square feet. The lawn care product you purchase states that, the contents of this bag covers 5,000 square feet. Therefore, you require 2 bags of this product to cover 10,000 square feet. You may ask now, what is the best technique to evenly distribute this product. Even distribution is usually assured with multiple passes in multiple directions over your lawn. Therefore, place your spreader on a light setting and continue to make passes over your lawn, changing directions with each pass until all the required material has been applied. This may require 3, 4, 5 or more trips over your lawn, but you can be certain that the distribution of the material is very good. In time, as you become familiar with your spreader and the products you use; you can fine tune your spreader to reduce the number of trip required.

Most fertilizers and lawn care products have tables on their bags with suggested settings for various brands of spreaders. If you are fortunate enough to own a spreader specified in the table, then; use that setting. Keep in mind that those settings are usually for one pass over the lawn. These application tables also assume a 3 mph walking speed. To give uniform applications, consider cutting the setting by 1/3 to ½, making two to three applications to avoid skips. This might be a way to decrease the number of trips you have to make with the above method.

For those wishing to know specific calibration techniques of rotary spreaders, please refer to MU Guide Sheet WQ551 – Calibrating Home Garden Equipment @ http://extension.missouri.edu/explore/envqual/wq0551.htm.

Proper Mowing is Key to Healthy Lawns

Turfgrass plants improperly mowed are under greater stress. Greater stress means a lawn can be more susceptible to weeds, diseases and insects. Therefore, less stress from proper mowing practices equals fewer inputs ($) for a home owner or professional grounds manager.

Optimal cutting heights for coolseason grasses, such as blends of turftype tall fescues, should range from 3.0 to 4.0 inches. Warm-season grasses, like zoysia, can range between 1.5 and 2.5 inches.

Seasonal variation in mowing height was once thought to be highly beneficial and is still considered beneficial by some. We know that mowing cool-season grasses a little taller in the summer months can have benefits through summer stress periods (deeper roots, better cooling effect). Taller grasses will also conserve moisture, giving some reduction in irrigation requirements. We also know that cool-season grasses mowed a little taller in the spring and fall compete more successfully against weeds (up to 80 % control of annual weeds). Therefore, select the tallest, acceptable mowing height for your species of grass and maintain that height during the entire season. This provides benefits throughout the season -- competition against weeds as well as reduced summer stress.

Clippings should be uniformly distributed rather than deposited in clumps. Mowing the lawn when the grass is dry and using a properly sharpened mower blade will spread clippings evenly. If some areas produce excess clippings, simply mulch those in with a second passing of the mower.

Mowing creates wounds through which fungi can enter the plant and infect it. Leaf cuts made by a sharp mower blade are cleaner and heal faster than the tearing and shredding caused by a dull mower blade. A dull mower blade inflicts more and bigger wounds that increase potential for infection by turfgrass diseases. Having a sharp, spare mower blade allows you to switch blades when needed and prevents delays in mowing when getting your mower blade sharpened.

Observe leaf tips or grass clippings collected on your mower deck immediately after a mowing to determine the quality of cut. Use this as an indicator of when to sharpen mower blades.

During hot summer months it is best to mow later in the day to minimize additional stresses on your grass.

It is also best to change directions of mowing each time you mow.

Frequency of cut should be determined by the “one-third rule” of mowing. You should make sure that no more than one-third of the leaf growth is removed during a single mowing. During the spring and fall, cool-season grasses can be mowed every 5 to 6 days.

Many homeowners believe grass clippings need to be removed to have a healthy, vigorous lawn. By following the steps in the “Don’t Bag It” lawn care program, you can have a beautiful lawn without collecting your grass clippings (MU Guide G6959 – “Don’t Bag It” Lawn Care: How to Recycle Your Grass Clippings, Leaves and Branches). Returning grass clippings can return as much as 35 percent nitrogen and 50 percent potassium. Grass clippings also contribute to the organic matter levels of your soil improving the water and nutrient holding capacity of the soil.

When is it OK to bag clippings? 1) When delayed in mowing due to rain; 2) When you wish to make compost (Refer to: MU Guide G6956 – Making and Using Compost & G6958 – Grass Clippings, Compost and Mulch: Questions and Answers); and 3) When preparing for aeration and over-seeding in late summer to early fall. Avoid using grass clippings in compost when chemically treated.

A word of caution about weedeating: Weed-eaters typically scalp turfgrasses when edging along sidewalks, curbs, and driveways. This promotes weeds! Best edging practices include a power edger or weed-eater (rotated) with a vertical blade preventing any scalping of turfgrasses.

Fertilizer Schedules

Feed turfgrasses when they are actively growing (Synthetic Fertilizers - Table 1). Cool-season grasses should be fed primarily in the fall with some fertilizer applications made in spring. Many spring applications are in the form of fertilizer impregnated with preemergent herbicides for annual grassy weed control (crabgrass preventers – applied by April 15th). Warm-season grasses should be fed after initial green-up in the spring. They can be given N fertilizer during each month of active growth (May through August for nitrogen only; potassium applications in September).

Late-season nitrogen fertilization, sometimes referred to as late-fall fertilization, has been used by turf managers for years. This type of fertility program involves the application of much of the season’s nitrogen during the late season months of August through October or November (dependent upon location). It is important that late-season fertilization not be confused with dormant or winter fertilization. The latter method implies that fertilizer applications are made after the turf has lost most of its color during late fall or winter and is not actively growing. This differs notably from the late season concept, which requires that nitrogen be applied before the turf loses its green color in the fall. Late-season fertilization has become popular because of many agronomic and aesthetic advantages, which include: better fall and winter color, earlier spring green-up, increased shoot density, improved fall, winter and spring root growth, and enhanced storage of energy reserves (carbohydrates) within the plant.

It is important to remember that the nitrogen source used for fall application be a type that is not heavily dependent on microbial activity to cause the nitrogen to release. This means that fertilizers containing urea, sulfur-coated urea (SCU), IBDU, shorter-chain methylene ureas and ammonium sulfate are ideal N sources for the late-season applications. Although SCU and IBDU are referred to as controlled-release fertilizers, the rate at which nitrogen is released from these fertilizers mainly depends on soil moisture and not on the degree of microbial activity. The use of microbedependent N sources for late-season applications may not elicit the desired fall/winter color response because they do not provide enough available nitrogen for plant uptake when temperatures are low. However, these slow-release N sources would be ideal for spring and summer use. Examples of these would be natural organic nitrogen sources and fertilizers consisting mostly of longerchain methylene-ureas (low in coldwater soluble N). Research has shown at several universities that natural organic fertilizers, such as Bradfield, Milorganite, Sustane, Ringer, Nature’s and Organica, perform well in home lawn fertilization programs (See Table 2 and 3 for organic fertilizer schedules). A product like Organica, a corn gluten-based fertilizer, can also provide some preemergent activity for annual grass and broadleaf weed control.

Table 1. Nitrogen application scheduling
  SEPTEMBER OCTOBER NOVEMBER MARCH to APRIL
Standard cool-season
Low-maintenance
cool season
1.0¹
1.0
1.0
1.0
1.0
0.5-1.0²
0.5-1.0
  MAY JUNE JULY AUGUST
Standard warm-season
Low-maintenance
warm season
0.50
0.50
0.50
0.50
0.50
0.50
Notes:
¹ All rates are in pounds of nitrogen (N) per 1,000 square feet.
² The spring application may be made with a combination crabgrass preventer.
Table 2. Application Schedule for Organic Fertilizers Cool-season Grasses
(Rates are expressed in pounds of nitrogen per 1,000 sqft)
Coolseason Grass No Fall Seeding Early April:
Corn Gluten* Product 0.8-1.2
Late June:
Corn Gluten or other Organic Product 0.4-0.8
Mid Sept.:
Corn Gluten or other Organic Product 0.8
Coolseason Grass Fall Seeding Corn Gluten Product 0.8-1.2 Corn Gluten or other Organic Product 0.4-0.8 Do not use Corn Gluten, use another Organic 0.3-0.8
* Corn gluten based organic products offer some pre-emergence weed control for annual weeds and can affect turfgrass seed germination. Be sure to purchase corn gluten products that are in a granular formulation. They are much easier to spread.
Table 3. Application Schedule for Organic Fertilizers Warm-season Grasses
(Rates are expressed in pounds of nitrogen per 1,000 sqft)
Warm season Grass Mid April:
Corn Gluten* Product 0.8-1.2
Late June:
Corn Gluten or other Organic Product 0.4-0.8
Mid August:
Corn Gluten or other Organic Product 0.8
* Corn gluten based organic products offer some pre-emergence weed control for annual weeds and can affect turfgrass seed germination. Be sure to purchase corn gluten products that are in a granular formulation. They are much easier to spread.

Calculating How Much Fertilizer to Apply

The first of the three numbers on a fertilizer bag is the percent nitrogen (by weight), the second is percent P2O5 (not actual P), and the third number is percent K2O (not actual K). Percent nitrogen refers to the concentration of nitrogen in the fertilizer source. Natural organic sources are typically low in nitrogen concentration, while synthetic nitrogen sources are higher. Knowledge of this number allows one to calculate how much fertilizer to apply based on specific rates of nitrogen being applied per 1,000 square feet. If you want to apply 1 pound of nitrogen per 1,000 square feet of lawn area, you must apply Ringers organic fertilizer (9 percent N) at a rate of 11 pounds of fertilizer per 1,000 square feet. Knowing this simple calculation allows you to apply proper amount of nitrogen per 1,000 square feet regardless of the type of fertilizer or nitrogen type.

Proper Watering Methods

Nearly all diseases require water for their development. Some disease problems such as pythium blight, brown patch, and dollar spot are accentuated by extended periods of free moisture. Extended periods of free moisture in turfgrasses can be caused by dew, guttation fluids, and frequent irrigation or rainfall. Guttation is the formation of water droplets at the tips of grass leaves that contain exudates of sugars and proteins. These exudates serve as an excellent food source for diseases. Remove dew and guttation fluids from grass leaves by dragging a hose across the surface, using a whipping pole, or briefly irrigating only long enough to wash the dew from the surface. Following these methods will spread the concentrated dew or guttation over a larger surface area causing the turf canopy to dry faster.

Improper irrigation alone may create a disease problem that could have been prevented. Avoid frequent irrigation that results in extended periods of free moisture. Avoid late evening watering that extends free moisture period throughout the night. Cool-season grasses can be allowed to have drying periods (near wilting) to disrupt the growth cycle of fungi favoring free moisture.

Irrigation in the early morning not only limits extended periods of dew and guttation, but irrigation is also being applied at a time of the day when temperatures are low (reduced evaporation) and winds are calm (better distribution of water). A general rule of thumb is to avoid puddles and runoff during irrigation, put the water where it is needed, and irrigate only what your particular soil type can absorb in one cycle. Lawns need 1 to 1 ½ inches of water a week either from rain or irrigation.

Benefits of Timing of Aeration:

Aeration is a practice of pulling soil plugs to open the soil surface for better air, water and nutrient movement. It is a practice that also helps to reduce compaction and thatch by spreading soil plugs on the surface. Soil plugs are crumbled and fall freely into aeration holes as well as spreading some soil into the thatch layer where soil microbes can feed on thatch debris. Aeration is a practice that can be done in both spring and fall.

Aeration is the very best way to begin a fall fertilization program. Applications of fertilizer after aeration will move nutrients immediately into the root-zone of your lawn. This practice has shown excellent results in the density and color of cool-season turfgrasses on their way to recovery from summer stresses.

Aeration is also an excellent practice prior to fall over-seeding. If lawns show some thinning from a stressful summer, over-seeding is recommended to maintain the density desired for a quality lawn. Aeration prior to seeding will help ensure better seed/soil contact for improved germination.

Aeration equipment can be found at local rental stores or garden centers as well. A machine that pulls a ½” diameter plug three to four inches deep on four inch centers will do an excellent job. Machines that force hollow tines into the soil are better than pull-type drums with tines. Not all machines will meet these specifications; however any amount of aeration is better than no aeration to kickoff fall fertilization and over-seeding.

Why We Over-seed:

A thick lawn mowed tall (3 ½ to 4 inches) is your best natural weed control. Over-seeding of cool-season grasses should occur in September to maintain the density required for competition against weeds. Lawns showing some thinning from summer stress can be over-seeded with half the amount of seed used in a normal establishment or renovation. Normal seeding rates for turf-type tall fescue blends range from 7 to 9 pounds/1,000 square feet. Mixtures of tall fescue with Kentucky bluegrass in a 95/5 ratio should be seeded at the same rate for a normal seeding. Therefore, over-seeding rates for these grasses should range between 3.5 to 4.5 pounds/1,000 square feet. As with fertilizers and other lawn products, we recommend applying seed at a half rate in two directions to provide better distribution of the seed.

Keep in mind that it is always important to have good seed/soil contact for better seed germination. Covering seed with light amounts (1/4”) of good quality compost is another means to help germination and improve the soil. When seeding small bare areas avoid using straw since straw contains some weed seed. Some good commercial mulch, such as PennMulch or Straw Net, can be used and do not contain any weed seed.

Keep soil moist for several weeks until seed germinates. Frequent, light waterings may be needed to keep soil surface from drying out and affecting seed germination.

Begin mowing just as soon as grass reaches desired height to promote tillering and improve density. Mowing grass frequently in the fall will also mulch down fallen leaves.

Managing Common Turfgrass Pests: Weeds, Diseases, Insects and Moles:

Whatever pest problem you are having, there are five basic steps to pest management:

  1. Properly Identify the key pest and the damage it may cause,
  2. Monitor pest populations regularly,
  3. Determine the potential for economic loss from the pest,
  4. Select the proper pest control tactic, such as cultural, biological or chemical,
  5. Evaluate the control measure used.

Weeds:

A weed is simply a plant out of place. Any plant that is disrupting the desired aesthetic quality, performance or functionality of a turf area is a weed. Weeds are opportunistic and can become a problem under several situations: improper management (mowing height and frequency, fertilization, irrigation), soil disturbance, thinned areas due to traffic, diseases, insects and poor establishment. A turfgrass weed control program involves any practice that will prevent weed development in a turf, or shift factors favoring weed development to the point that turf growth and health are favored instead. The primary step in any pest management program is proper identification. Proper weed identification is necessary before a decision can be made about control. It is possible that a simple change in a cultural practice could prevent a weed problem or at least decrease population levels below economic or aesthetically disruptive levels. However, in some situations, the use of chemical pesticides may still be needed.

Diseases:

Selecting disease resistant varieties of turfgrass species is the foremost best step to reduce potential disease problems. Using good turfgrass management practices that lead to a healthy plant is the second. Managing plant growth and carefully selecting the appropriate varieties for your conditions come next. Knowing some information about what diseases favor —especially any that have historically been at that site— can give the homeowner a heads-up on prevention of turfgrass diseases. A couple of examples include: Dollar spot is a disease that favors lower fertility, primarily infects bluegrass and ryegrass, and likes 80-degree days with moderate humidity and nighttime temperatures in the 60s that produce heavy morning dews. Brown patch favors high nitrogen in turfgrasses, primarily infects fescues, ryegrass and bentgrass, and likes 90-degree days with high humidity and nighttime temperatures above 70 degrees. This information would help you decide how to change management/cultural practices to favor your lawn and not the disease.

Insects:

While insects are one of the most populous forms of animal life on earth, only a small number of insects may, at some time in their life cycle, become a potential threat to turfgrass. Turfgrass insects can be somewhat cyclical, and population levels depend on a number of factors, including weather, suitable food sources, desirable habitat and predators. Turfgrass damage is usually not observed until the numbers of an insect species reach a threshold level. Insects may always be present, but not always at damaging levels. For example, a homeowner would not need to treat if only one or two white grubs are found while doing yard work. However, if the homeowner peels back dead sod and finds more than five annual white grubs per square foot, then treatment is called for. Turfgrass pests cannot be controlled over long periods of time solely through the use of pesticides. To have a healthy and vigorous turfgrass, it is necessary to use pesticides in combination with sound cultural practices.

A healthy, growing plant is the best defense against turfgrass pests. Many plants become more susceptible to pests if they are stressed. Following good turf management practices with mowing, proper watering, fertility, aeration, thatch control and overall sanitation (leaf litter, mulches and other debris) produces good, healthy, dense turf that is pest-resistant.

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