Lawn Diseases

Bahia Grass

 

 

 

 

Brown Patch Fungus

Brown Patch causes unsightly patches of blighted turfgrass and is capable of infecting and killing most turfgrass species. During long periods of hot, wet and humid conditions, brown patch can develop rapidly so that large blighted areas occur within 24-48 hours. Turfgrass usually recovers from light attacks in 2-3 weeks with treatment. This fungus survives on decaying organic matter or in soil, but will use living plant tissue if available. Symptoms of brown patch vary greatly depending upon turf species, mowing height, soil, and environmental conditions. In low cut turfgrass, symptoms appear irregularly blighted patches of a few inches to 2 feet in diameter, especially evident during mornings of warm humid weather. A feature is a dark purplish gray smoke-ring border on diseased areas, especially on short-cut turf.

 

Buckhorn Plantain

Buckhorn plantain (plantago lanceolata) is a perennial with a distinctive rosette of egg-shaped leaves. Its presence indicates very low calcium, very high potassium, very high magnesium, high sodium, high chlorine, and low humus.

 

 

 

Chickweed (Common) & Mouse Ear Chickweed

Chickweed is a winter annual with numerous branched stems. It has white flowers in small clusters at the ends of the stems. Its presence indicates very low calcium, very low phosphorus, very high potassium, high sodium, and low humus levels.

 

 

 

Clover (Hop & White)

Hop clover (trifolium agrarium) is a perennial with hairy-branched stems. It has altering leaves with three leaflets and numerous bright yellow flowers on long stalks. Its presence indicates very low calcium, high magnesium, low humus, and sticky soil.

White clover is a low-growing perennial with creeping stems. It has oval leaves and white flowers arranged in round heads. Its presence indicates high magnesium, high sodium, and high chlorine.

 

Crabgrass

Crabgrass is a spreading summer annual. It has a seedhead with two to six finger-like branches. The best control for crabgrass is pre-emergent.  Crabgrass can be found in most warm, moist, fertile lawns in sun where turf is thin or mowed too short. It will tolerate hot, dry, compacted soils after establishment, and may spread aggressively to crowd out desirable grasses. The seed can germinate from mid-spring through summer when soil temperatures are greater than 55 to 60 degrees F for 7 – 10 consecutive days and can continue germinating in soil temperatures to 95 degrees F.  Its presence indicates very low calcium, very low phosphorus, high potassium, high magnesium, very high chlorine, and low humus.

 

Dallisgrass

Dallisgrass (paspalum dilatum) is a perennial with leaves that are smooth on both surfaces with a few long hairs at the leaf base. There is no pre-emergent control for dallisgrass. Its presence indicates low calcium, high potassium, very high magnesium, high chlorine, and low humus.

 

 

Dandelion

Dandelion is a deeply taprooted, stemless perennial. It has deeply cut leaves and a single yellow flower at the end of each hollow stalk. Its presence indicates very low calcium, very high potassium, high chlorine, and low humus.

 

 

Dollar Spot Fungus

Dollar spot occurs on all turfgrass species. Dollar spot occurs from late spring to late fall and is most prominent after cool moist weather. Temperatures between 60 and 85 degrees F and long periods of leaf wetness from dew, rain or sprinkler irrigation favor growth of this fungus. Prolonged wet foliage is a key factor. Growth of the fungus is inhibited when temperatures exceed 90 degrees F. Spread to new areas occurs primarily by wind and water. Turfgrass growing under dry soil conditions is more susceptible than when adequate soil moisture is provided. Damage is usually more severe if there is a deficiency or great excess of nitrogen.

Symptoms of the disease first appear as tiny yellow spots on individual grass blades. The spot expands to a straw colored or tan band with dark reddish-brown margins. The tip of the affected leaf often remains green. The tan band, or lesion, is often narrower in width than the leaf, resulting in the lesion taking on an “hourglass” shape. The entire blade soon becomes bleached. As the grass dies and the infected areas enlarge, light straw-colored spots 2-3 inches in diameter appear in the lawn. A fine, cobwebby white mold may be visible early in the morning when heavy dew is present. The turf in these spots may be killed all the way from the lesion to where the plant comes into contact with the soil. If left unchecked, the spots may merge and form large, irregular straw-colored patches.

 

Foxtail

 

 

 

 

Goose Grass

 

 

 

 

Gray Snow Mold

 

 

 

 

 

 

 

Leaf Spot

 

 

 

 

 

 

Necrotic Ring Spot

Necrotic ringspot (NRS) is the most destructive disease of Kentucky bluegrass in Colorado. The disease also damages red fescue and annual bluegrass. Necrotic ringspot is particularly damaging to bluegrass because it is a perennial problem and the fungus attacks and kills the roots and crowns. Recovery from a disease outbreak is often very slow.

Necrotic ringspot is caused by a soil-borne fungus called Ophiosphaerella korrae. The fungus survives from year to year on dead, colonized bluegrass roots and crowns or on the surface of living roots. The fungus actively colonizes the outside of roots at soil temperatures between 65 and 80 degrees F. These temperatures occur from mid-May through mid-September along the Front Range, but may vary somewhat on the west slope and at higher elevations. The fungus eventually penetrates roots and colonizes the root cortex.

This either debilitates or kills roots and leads to a decrease in water and nutrient uptake by the plant. Plants with extensively damaged root systems are more prone to injury or death, particularly during periods of high temperature or drought stress. Thus, NRS symptoms often don’t show up until late summer or early fall even though root colonization occurs throughout the summer. Symptoms may persist through the winter. 

Bluegrass affected by NRS exhibits extensive root and crown discoloration and rot. This can be observed by cutting a small sod piece from the lawn and carefully washing off soil and organic matter from roots. Darkly pigmented fungal threads may be visible with a hand lens on the root surface. The presence of large frog eyes and root discoloration are usually diagnostic for NRS. However, NRS can be confused with another disease called summer patch. Plant disease diagnostic labs can verify the presence of NRS.

Necrotic ringspot often appears two to three years after lawn establishment, although in some cases the disease may not develop for a decade or more. Initially light green to straw colored patches from several inches to several feet in diameter develop in the lawn. The patches may be localized to one part of the yard or widely scattered. As the disease progresses, patches develop more of a doughnut or frog eye pattern. The ring becomes matted and crater-like whereas the grass inside the ring remains healthy and green. Rings may eventually unite to create larger arcs of dead turf. Symptoms may persist through the growing season and increase in size and severity in successive years.

The disease begins as scattered light green patches 2-4 inches in diameter. Circular patches over a foot in diameter appear in the spring, fade with warmer temperatures and then reappear with heat and drought stress. The pattern in the lawn will resemble a "frog-eye" shape. In frog-eyes, an apparently healthy green patch of grass is partially or completely surrounded by a ring of dead grass. Distinct streaks, crescents and circular patterns are found in the affected lawn area.

Treatment:

• Treat areas of fungus with a proper fungicide
• Eliminate excess thatch to have no more than 1 inch in thickness by power raking in the spring.
• Don't mow to low and mow often enough that less than 1/3 of the leaf blade is removed during each mowing
• Avoid fertilizer with a high concentration of Nitrogen, especially in the hottest 3 summer months of June, July & August
• Aerate at least twice a year
• Water disease prone areas to a depth of 6-8 inches every 7-10 days during dry periods in the summer
• Regular fertilizing program with low nitrogen levels
• The harmful effects of excessive temperatures can be reduced by a light sprinkling of the turf mid-day
• Water prior to the application of fungicide if possible
• Applying top dressing is another option for severely damaged lawns
• Reseed dead areas with a mixture seed of perennial ryegrass seed with resistant bluegrass seed to help surpress NRS

 

Nutsedge (Purple)

Purple nutsedge (cyperus rotundus) and yellow nutsedge (cyperus esculentus) are rapidly spreading perennials with flat leaves that are usually shorter than the flowering stem. They reproduce primarily by tubers. There is no pre-emergent control for nutsedge. Its presence indicates very low calcium, high potassium, high magnesium, low humus, low bacterial count and anaerobic soils.

 

 

Onion-Wild

Wild onions (allium canadense) are cool-season perennial with slender, hollow cylindrical leaves. Its presence indicates very low calcium, high magnesium, low humus and a low bacterial count.

 

 

Oxalis

Oxalis (oxalis pes-capre) is an upright perennial with hairy stems. It has alternating leaves with heart-shaped lobes and bright yellow flowers with five petals. Its presence indicates very low calcium, high magnesium, and low humus.

 

 

 

 

 

Pythium Blight

Pythium blight, sometimes called cottony blight, is one of the most destructive turfgrass diseases. Susceptible turfrasses include perennial ryegrass, creeping bentgrass and tall fescue. Injury to Kentucky bluegrass , bermudagrass and zoysiagrass is rare in residential landscapes. Symptoms of Pythium blight are variable depending on the turfgrass species affected and the height at which the grass is cut. On bentgrass and perennial ryegrass mowed at fairway height, the first symptoms are small, irregularly-shaped, water soaked, greasy patches up to 4 inches in diameter. A cottony growth may be present in patches early in the morning. The patches may merge and form streaks since the fungal-like organism may be spread by mowing equipment or water. Diseased plants eventually turn straw color and wither, resulting in crater-like depressions in the turf. Symptoms progress rapidly during favorable weather and large areas may be extensively damage within a matter of days.

Pythium blight is erroneously believed to be common on creeping bentgrass putting greens. In fact this disease rarely occurs on bentgrass mowed less than ¼ inch in height. It is not uncommon to find Pythium blight on the putting green fringe yet see no damage on the putting surface.

Pythium blight occasionally affects tall fescue during hot, humid weather. Softball-sized patches of water-soaked turfgrass form during hot wet conditions. Diseased grass blades within the patch tend to stick to one another and have a mushy texture. Spots may coalesce and streaks may also form. Pythium blight will commonly develop along water drainage patterns in the turf. Affected plants eventually wilt and die to the crown. However, crowns and roots may not be killed and plants may recover after several weeks.

Pythium blight may also be a common cause of damping off and seed rot during turfgrass establishment.

 

Red Thread

 

 

 

 

Slartibartfast

 

 

 

 

Spurge (Prostrate)

Prostrate spurge (euphorbia maculata) is a summer annual with freely branched hairy stems. It has opposite leaves, usually with a reddish spot.  It is a low growing plant that often forms a dense mat. The stem, when broken, exudes a milky latex juice. This plant does not like competition and depends on its prolific seed production for survival. A single plant is capable of producing several thousand seeds. Seeds are small and can remain dormant in the soil until conditions are suitable for germination.Its presence indicates low calcium, very high potassium, very high magnesium, high sodium, very high chlorine, and low humus levels.

The primary method of managing spurge should be prevention – it is very difficult to control this weed once it is established. Keeping a healthy full lawn free of open areas is best for control. Where open areas develop in the turf either from stress, disease, insects, rodents etc., light is able to penetrate to the soil surface, allowing spurge to germinate. It will help to not mow your lawn shorter than 2 inches.

 

Summer Patch

 

 

 

 

 

 

Thistle

 

 

 

 

 

 

Insects

Cinch Bugs

 

 

 

Fleas

 

 

 

 

Grubs

 

 

 

 

Spider Mites

Spider mites are among the most serious pests of ornamental plants. They feed on the underside of the leaves by sucking the juice out of the tissue. Because of the small size and the fact that the suck from the underside of the leaves, they are often overlooked until serious damage occurs.