Turf - Rust in the Fall

Rust is a common problem on ryegrass and Kentucky blugrass in the fall. The following is more information.

Rust on perennial ryegrass and other turfgrasses is favored by the cool, moist weather of fall. Look for yellowing of turf. Close examination of the individual grass blades will reveal the reddishorange pustules of the rust fungus. It can cause some thinning of turf but the best treatment at this time of year is fertilizing the lawn. Lawns will outgrow the fungus in most cases. Rust is usually a low fertility, low vigor problem on turf.

A variety of related fungi cause rust. Ccommon names include leaf rust, crown rust, and stem rust, and the disease occurs almost exclusively on Kentucky bluegrass and perennial ryegrass. Rust is largely cosmetic, but the orange spores that dislodge easily from leaf surfaces can be a greater nuisance, covering shoes, pets, and lawnmowers with a rusty residue. Rust can severely damage new spring-seeded lawns that lose vigor during heat and drought conditions.

From a distance, rust-infected turf appears chlorotic. Symptoms occur in a diffuse pattern around the initial site of infection as disease increases. Outbreaks often first occur in shaded or protected areas, such as around the bases of evergreens or next to a structure’s foundation. Close inspection of rusted leaves reveals numerous yellow-orange pustules on leaf blades. Walking through grass with significant amounts of infection will disturb and release the spores within these pustules and leave a distinct orange color on shoes and pets. These spores, carried by the wind, spread the disease to other areas during the growing season. Rust outbreaks are most common in late summer and early fall, although sometimes the disease is active in the early spring, especially on poorly nourished turf. Rust is a disease of slow growing turf, so factors such as summer heat and drought stress, low nitrogen fertility, compaction, and shade contribute to poor growth tend to favor rust development. Rust outbreaks require moderate temperatures (50°-60°F) and long evening dew periods (more than 10 hours). The pathogen survives as resilient spores over the winter or as inactive mycelium in dormant turf.

Rust Control

Maintaining a healthy and vigorous turf stand is the most effective and efficient method of rust control. Since slow growing turf in late summer is most vulnerable to outbreaks, small amounts of nitrogen fertilizer (0.25-0.5 pound of N per 1,000 square feet) in chronic trouble spots—shaded and possibly compacted areas—will help control the disease. The nitrogen will promote leaf growth and allow for regular mowing, which helps the turf outgrow rust’s relatively slow infection cycle. Avoiding irrigation during the early evening also will help limit disease spread by lessening the chance of extended dew periods.

DMI and QoI (strobilurin) fungicides are very effective against rust, but on well-established turf, should be considered only as a remedial treatment when cultural practices fail to prevent an outbreak. On newly seeded stands, fungicides should be appliedat the first sign of disease. In most cases, a single application of an effective fungicide, combined with efforts to encourage turf growth, will quell outbreaks.


Rust on perennial ryegrass. Photo from the August 10, 2009 edition of Turf Tips from Purdue University

Information from Bob Mulrooney, Extension Plant Pathologist, UD in the Current Ornamentals Hotline from UD Extension and Rick Latin, Turfgrass pathologist in the August 10, 2009 edition of Turf Tips from Purdue University

Turf - Brown Patch Season

Summer means brown patch disease season in turfgrasses. The following is more information.

Brown patch disease will be coming active in Delaware soon, especially in tall fescue. Warm, humid weather will promote brown patch activity on cool- season turfgrasses. Perennial ryegrass is probably the most susceptible host; creeping bentgrass and tall fescue are both relatively susceptible. Sometimes we see brown patch on Kentucky bluegrass, as well.

On all grasses, affected patches are often somewhat circular and can range from several inches to two or more feet in size. On tall fescue and Kentucky bluegrass, leaves exhibit tan, irregular lesions with a thin, brown border. On creeping bentgrass and perennial ryegrass, a ring of olive- green leaf blades appears on the outside margin of the patch; these blighted leaf blades dry to a tan color. On humid mornings, the mycelium of the fungus often appears as a sparse, very light tan webbing in the lower canopy. This can be best seen with a hand lens. In some situations on perennial ryegrass, the mycelium can be quite dense, cottony, and fluffy, and grow all over the leaf blades. In this condition, it can look quite a bit like Pythium cottony blight. Since different fungicides are used against Pythium cottony blight and Rhizoctonia brown patch, knowing the identity of the disease can be quite important from a management standpoint. Laboratory diagnosis is the best option if a case of perennial ryegrass has dense mycelium that looks like Pythium blight.

Management: During the next 8-10 weeks or so, be careful with postemergence herbicides, some of which have been shown to increase brown patch activity on cool-season turfgrasses.

Tall fescue. Generally brown patch can be managed through cultural means in established tall fescue lawns. However, recent seedings of tall fescue often can suffer severe outbreaks of the disease during humid weather in summer months. These should be monitored carefully and treated with fungicide if necessary. Once these swards make it through their first summer and are well-established, they often do not need fungicide treatment to maintain sward density, although fungicides do improve overall greenness during summer. Be aware that products containing chlorothalonil and iprodione are no longer labeled for use on home lawns.

Kentucky bluegrass. Although brown patch may be active in adapted varieties of Kentucky bluegrass, brown patch rarely develops aggressively enough on this host to justify fungicide treatment.

Perennial ryegrass and creeping bentgrass. High- maintenance perennial ryegrass and creeping bentgrass swards should have preventive fungicide applications on at this point, and putting greens should continue to receive preventive applications for brown patch control through August (and possibly later, depending on weather).

There is a wide selection of fungicides with very good activity for brown patch control. See the Extension publication PPA-1, Chemical Control of Turfgrass Diseases (http://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdf) for options.

Adapted from "Brown Patch Activity" By Paul Vincelli in the current edition of the Kentucky Pest News http://www.uky.edu/Ag/kpn/kpn_09/pn_090630.html

Turf - Red Thread

Red thread disease in turf has been found recently. The following is more information.

Red thread has been diagnosed in a mixed turf of bluegrass and perennial ryegrass. The infected patch had a pink cast with red fungal threads easily seen upon close inspection. Although considered a disease of stressed turf, all turf can be infected under these ideal conditions. Red thread only infects the blades causing temporary damage. Infected turf will recover with time. Fungicides applied at the first signs of infection may help reduce damage but treatment is not usually warranted.

Red thread is a foliar disease that usually occurs on taller mown turfgrasses during spring and fall. The disease is often associated with malnourished, low quality, slow growing turf, but the effects of the disease are largely cosmetic. Red thread symptoms create an undesirable appearance, but crowns and roots are not infected, so plants are not killed and turf eventually will recover.

Red thread most commonly affects Kentucky bluegrass, perennial ryegrass, and tall fescue. Outbreaks usually occur in low maintenance turf stands such as residential lawns, golf course oughs, and some low budget athletic fields. Red thread development is most common where turfgrass nutrition is poor and there are other factors that promote slow growing turf.

The most important nonchemical (cultural) control option involves implementing an adequate nitrogen fertility program. A good fertility program implemented over two to three years will drastically reduce further red thread problems. Other cultural practices that promote healthy turf and vigorous growth also help suppress red thread. Outbreaks may be reduced further by avoiding irrigation practices that extend dew periods (such as watering in the late afternoon and early evening).


Photo from the Purdue University fact sheet BP-104-W on red thread disease of turf.

Information from Bob Mulrooney, Extension Plant Pathologist, UD and Purdue University fact sheet BP-104-W by Philip Harmon, Graduate Research Assistant and Richard Latin, Professor of Plant Pathology http://www.ces.purdue.edu/extmedia/BP/BP-104-W.pdf

Turf - Red Thread Disease

The following is information on red thread disease of turfgrasses.

Laetisaria fuciformis, the causal agent of Red Thread, is now infesting susceptible perennial ryegrass and fine fescue turf. Infections are characterized by the appearance of short red threads (1/8” to 1/4” long) emerging from tan-colored leaf blades. Affected patches are typically pink in color and range from 1 to 6 inches in diameter. Kentucky bluegrass and tall fescue may also be affected in the spring. Red thread is typically found on “hungry” (low fertility) turf during cool, wet weather. Well-fertilized turf may also be attacked but to a lesser extent than nitrogen deficient turf. To obtain optimum disease control, maintain adequate fertility levels, keep turf properly irrigated, avoid excessive thatch, and apply Armada, Banner, Bayleton, Chipco 26GT*, Compass, Curalan*, Eagle, Endorse, Headway, Heritage, Insignia, Prostar, Rubigan, Tartan, Trinity or Touche* per manufacturer’s recommendations. (*Not for use on home lawns)

Red thread disease on bluegrass. Photo by Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org.

Information from Bruce B. Clarke, Ph.D., Specialist in Turfgrass Pathology, Rutgers University.