Kentucky Bluegrass
Perennial Ryegrass
Tall Fescue
Fine Fescues
Other Grasses
Seed Mixtures/Blends
Site Preparation
Sod Sources in Idaho
Main Nutrients
How Much to Apply
When to Apply
What Kind of Fertilizer
How to Apply
Mowing Height
How Often Should I Mow?
Clippings
Mowers & Maintenance
Type of Grass
Time of Year/Weather Conditions
Type of Soil
Sprinkler Systems
Billbugs
White Grubs
Earthworms
Diseases
Weeds
Thatch Prevention
Thatch Removal/Managment
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The larval stage of several insects cause damage to home lawns. The larvae feed on roots and underground stems of
grass. A thick, healthy lawn may not be resistant to insects, but will be better able to recover from injury and will be able to tolerate some damage without it being noticeable.
If you suspect insect injury, look closely in the thatch layer and top 1-2 inches of soil for larvae. Make sure you have correctly identified the insect and understand its lifecycle to determine the best course of action for control.
Billbugs
Billbugs are perhaps the most common insect affecting home lawns in Idaho. The adults,
which are about 1/4 inch long, can be seen in the spring, walking along sidewalks especially on the southern sides of buildings (Figure 1).
Figure 1. Adult bluegrass billbug crawling on a sidewalk.
(Photo courtesy: H.D. Niemczyk, Ohio State University)
The adults are a black weevil, have a long snout and will play dead when disturbed. The adults do very little damage, but
in the larval stage billbugs eat grass stems and roots. Adults start to become active when soil temperatures reach
55o F, usually early to mid-May. The larvae are small (1/8 -
1/4 inch long), white, legless grubs with a brown head (Figure 2).
Figure 2. Billbug Larva (right) and adult. (Photo
courtesy: H.D. Niemczyk,
Ohio
State
University
).
Lawns damaged by billbugs look like they are drought stressed because the grass blades are basically severed from the roots. Grass blades can be easily pulled out by hand with a light tug. A healthy, vigorously growing lawn will recover from moderate billbug damage and symptoms may go unnoticed. However, under-fertilized lawns or lawns that are otherwise stressed will be more susceptible to billbug damage.
Control. If you have areas with known billbug problems, control measures should be targeted against the adults in the spring when they are active and seen crawling along sidewalks or other exposed areas. Waiting until damage is visible may be too late since the damage has already been done. If targeting larvae, good coverage and movement of the insecticide past the thatch layer are very important. Since adults are on the surface of the turf, they are more easily contacted with insecticides.
Additional pictures of billbugs and other lawn insects can be found at:
http://hcs.osu.edu/plantfacts/pest/
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White Grubs
White grubs are the larval stage of a beetle known as scarab beetles or more commonly as May/June beetles and masked chafers. Their bodies have a characteristic "C" shape, are creamy white, have three pairs of
legs and grow to a size of up to 1-1 1/4 inches long..
Figure 3. White grubs in grass root zone.
(Photo courtesy: A.J. Koski, Colorado State University)
White grubs feed on grass roots causing severe wilting and eventually death of affected lawns.
The sod will tend to lift away when pulled, but grass blades will
generally stay intact since the grubs have eaten mainly roots.
Additionally, skunks and raccoons in search of larvae will cause considerable damage as a
result of their digging and feeding on grubs.
Grubs are generally found in the top inch or so of the soil and will go much deeper during the winter months. Masked chafer grubs have a one-year life cycle overwintering as larvae with the adults emerging in mid to late June. The May/June beetles on the other hand have a three-year life cycle with adults emerging in May and June, laying eggs and the larvae feeding during the summer and overwintering. The second year, when most of the damage occurs, the grubs feed throughout the summer. In the third year, the grubs complete their development in the spring and early summer, forming pupae and adults the following year to start the cycle again.
Control. Many insecticides are labeled for white grub control, however, it is very difficult to control white grubs because of the difficulty of getting the chemical into the soil where they are active. Excessive thatch can impede the movement of the chemical into the rootzone where grubs are feeding.
Core aeration can help increase the effectiveness of insecticide applications. Proper watering will also help, but it is important not to over water. Over-watering can actually decrease the effectiveness of insecticides.
Additional information on billbugs and white grubs can be found at:
Colorado State University: www.ext.colostate.edu/pubs/insect/05516.html
Earthworms
Earthworms and night crawlers are the main cause of bumpy lawns, a common complaint of many homeowners. Worms leave castings or small mounds of soil on the soil surface. These mounds soon dry and harden causing an uneven surface which can be somewhat bothersome during mowing operations. It is important to remember that the benefits of earthworms far outweigh the nuisance caused by these castings. Earthworms help decompose thatch, improve water, air movement and soil structure for good root growth. Earthworms are indeed a good indicator of a fertile soil.
Extremely bumpy lawns may also be an indicator of other problems such as a thin
turf stand due to a poor fertilization program. Following good fertility and watering guidelines will keep a lawn growing vigorously and will make bumps less noticeable.
In severely bumpy lawns, rolling in conjunction with aerifying may help reduce the problem
(http://www.ext.colostate.edu/ptlk/1508.html),
but generally, lawn rolling is not advised since it can lead to soil compaction
(http://www.ipm.iastate.edu/ipm/hortnews/1993/4-28-1993/bumps.html).
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DISEASES
Home lawns in southern Idaho are generally not faced with many disease problems because of the dry climate. Improper fertility or irrigation practices are generally the main cause of disease problems. Cool, overcast weather conditions or areas with excessive shade also can contribute to disease outbreaks. Generally, however, a properly managed lawn will be resistant to severe disease outbreaks.
Powdery mildew
Shady areas with Kentucky bluegrass are especially susceptible to powdery mildew. Powdery mildew appears as a white, powdery mass on grass blades and large affected areas appear as if they have been dusted with flour or talcum powder (Figure 4). It is favored by cool, humid, shady conditions and may even appear after cloudy weather. Poor air circulation and heavy fertilization worsen the problem.
Figure 4. Kentucky bluegrass growing on the north side
of a building.
Note that the thin stand and white powdery mildew on the leaves
closest to the wall.
(Photo: T.A. Salaiz, Univeristy of Idaho)
Control. If possible, trim trees to minimize shade and improve air circulation. Powdery mildew is rarely serious enough to warrant control with fungicides. Overseed shady areas with shade tolerant grasses such as
fine fescues or tall fescue.
Additional close up pictures and disease descriptions can be found at the following website:
www.ipm.iastate.edu/
Rust
Rust is an orange colored fungus that affects the grass blades. Heavily infested lawns will leave a rust-colored dust on shoes and clothing. Rust is usually a result of under fertilized and/or drought stressed turf. Cloudy, overcast conditions can also favor rust development. Light, frequent watering will keep leaf blades wet and also increase the development of rust.
Control. Generally, good fertilization and watering practices will prevent rust from occurring. Preventative fungicides are available, but generally not warranted for home lawns.
Additional information and photos can be found at:
http://extension.missouri.edu/extensioninfonet/article.asp?id=1107
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Fairy ring
Dark circles or partial circles of lush green grass in a lawn are caused by mushroom type fungi living in the soil. These dark circles of grass are commonly referred to as fairy rings. Sometimes mushrooms will appear following wet, humid weather. In severe cases, a ring of dead grass will appear inside the ring of green grass
The fungus that causes fairy ring grows on organic matter buried in the soil. As the fungus breaks down organic matter, nitrogen is released causing the green lush growth. In some cases, the growth of the fungus is so thick in the soil that water can not penetrate, causing the grass to become drought stressed and die.
Control. Prevention of fairy ring involves removal of tree stumps and other wood materials from a lawn site prior to establishment. If fairy ring still appears, it can be very difficult to remove the fungus entirely. Core
aeration and hand watering the affected area will help move water into the affected soil and help introduce other microorganisms that will compete with the fungus. Make sure to clean
aeration equipment to avoid introducing the fungus to other areas of the lawn. Proper fertility and watering practices will help reduce the severity of the symptoms and in some cases prevent fairy ring from developing. Fungicide drenches have shown irregular success and are generally not recommended for home lawns. Severe fairy rings with large areas of dead grass may warrant removal of grass and soil from the rings followed by introducing new soil and re-seeding the area.
Weeds
Most weed problems on lawns are associated with a weak, thin turf that allows sunlight to
reach the soil surface and weed seed germination. A thin turf is easily pushed aside by aggressive weeds which can become worse over time. Make sure and follow good fertility, irrigation and mowing guidelines to build a thick, vigorously growing lawn. Heavy populations of weeds are usually an indication of some other inherent problem with the lawn.
Some perennial weeds, like white clover, can still become problems even in well managed lawns. Many herbicides are available to effectively control weeds on lawns, but their success depends largely on proper application, and perhaps more importantly on correct timing. Understanding what weeds you have will help you determine the best time of the year to control them.
Realize that it is impossible to eradicate all weeds from a lawn even with herbicide use. Learn to tolerate some weeds in your lawn and avoid indiscriminate use of herbicides which can
injure trees, surrounding landscape plants and even the lawn itself.
Photographs of many weeds can be found at the following website: http://www.wssa.net/Weeds/ID/PhotoGallery.htm
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Perennial Broadleaf Weeds
Some common perennial broadleaf weeds on home lawns include dandelions, field
bindweed (also called morningglory), white clover, curly dock, ground ivy,
Canada thistle, broadleaf
plantain, buckhorn plantain, and yarrow. Make sure and properly identify the weeds before choosing herbicides for control. University of Idaho extension
educators, master gardeners and nursery personnel can help you with correct identification.
Broadleaf weeds can be controlled with postemergence herbicides which kill weeds that are actively growing. Postemergence herbicides do not prevent weeds from germinating.
The best time of the year to control perennial weeds is in the
late summer or early fall when the weeds are preparing for winter. In their winter preparation, perennial weeds move energy reserves down to underground stems and roots, so a herbicide application at this time will insure movement of the herbicide to these plant parts. Spring applications to perennial weeds can slow their growth and may kill them, but it is more difficult at this time. Regardless of when applications are made, make sure the weeds are growing actively at time of application. Avoid mowing for 1-2 days before and after the application to insure maximum uptake of the herbicide by the weeds.
There are many broadleaf weed control products available for home use. These products will contain one or a combination of the following chemicals: 2,4-D, 2,4-DP, MCPP, MCPA and dicamba. They are safe to use on cool-season lawn grasses. Liquid and granular formulations of these chemicals are available. It is very important to properly calibrate sprayers or granular spreaders to insure accurate, uniform application and avoid spraying adjacent flower beds. Be sure and read the label application directions.
Perennial Grassy Weeds
Perennial grassy weeds are the most difficult weeds to control in a home lawn. Some common perennial grassy weeds include:
quackgrass, roughstalk bluegrass, smooth bromegrass, annual bluegrass
(there exist some perennial biotypes) and even other cool-seasongrasses such as tall fescue and creeping bentgrass. There are essentially no herbicides available for the selective control of these weeds in a lawn. Removal prior to establishment and the use of high quality seed or sod is essential to preventing these weeds from becoming a problem. Many home lawns are established with poor quality seed that has high amounts of
weeds such as annual bluegrass and roughstalk bluegrass. This information is readily available on the seed label, but most homeowners are unaware of its importance. If small patches of perennial grasses are found in a lawn, physical removal with a shovel or spraying with a non-selective herbicide such as glyphosate is the only option followed by re-seeding or sodding the bare areas.
Annual Grassy Weeds
Weeds like crabgrass and foxtail are warm-season grasses that germinate from seed in the spring and infest lawns during the hot days of summer. They tend to invade lawns along sidewalks and driveways where temperatures are hottest and lawns are thin. Thick, vigorously growing lawns will out-compete most annual grassy weeds.
Annual grassy weeds are best controlled with pre-emergence herbicides which kill germinating weeds. These herbicides must be applied well before the weeds germinate since they will not kill weeds once they have emerged.
Additionally, some of these pre-emergence herbicides are impregnated on
fertilizer granules and applied as a weed and feed. Crabgrass will germinate when soil temperatures reach
55-60o F. This occurs around mid-March to early April for the Treasure Valley, Magic Valley and northern Idaho and late March to mid-April for central and eastern Idaho.
There are some herbicides that will kill young annual grass weeds, but they usually only work well on very young plants so application timing is critical.
Do not overseed into areas that have recently been treated with pre-emergence herbicides because the chemical will kill emerging lawn grasses as well. Check the label of the herbicide to see how long you need to wait before planting into an area treated with pre-emergence herbicides.
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