Red Thread

Let's discuss a common disease that occurs in lawns mostly during the fall and winter months. It’s called Red Thread (Laetisaria fuciformis). The disease is very easy to correct with a simple application of iron (no nitrogen is necessary), which will also help control moss. In severe cases, you will need to apply iron three to four times (or more) from fall through late spring. Most diseases (whether it be on lawns or any other kind of plants) happens when plants are weak from lack of proper nutrients. The disease is especially severe on slow-growing and iron deficient turf. All turf and lawn grasses are susceptible to this disease especially bluegrasses (Poa sp.), fescues (Festuca sp.), ryegrasses (Lolium sp.), and bentgrasses (Agrostis sp.) can be affected. Fine-leaved fescues and some ryegrasses are particularly susceptible.

BE CAREFUL NOT TO ALLOW THE IRON TO COME IN CONTACT WITH WOOD, CEMENT, BRICK OR ANY OTHER MATERIAL. IT WILL PERMANENTLY DISCOLOR AND STAIN!

Symptoms

The first noticeable symptoms are water-soaked patches of grass in the fall through spring. Infected grass blades soon die and fade to a bleach-tan color when dry. The infected leaf blades, are often mixed with healthy unaffected leaf blades giving the grass a ragged appearance (the left picture). In severe cases, most leaf blades may be killed and diseased grass looks scorched or yellowed in irregularly-shaped or circular patches. The patches may be widely scattered or, if close together, may combine into larger spots.

In humid weather, the fungus grows visibly on the infected grass blades and leaf sheaths. The fungus produces thread-like strands or web-like areas of coral-pink to blood-red hyphae on the tips of brown grass blades (the picture to the right). The strands can protrude up to 2 cm upward from the blade tips and are easily seen, hence the name "red thread disease".

Disease Cycle

Laetisaria fuciformis may produce spores for dispersal, however, the primary means of dispersal is the spread of infected tissue and bits of the "red thread" (sclerotia) to healthy areas of grass. This type of spread depends upon mowing, foot traffic, and other activities which occur on the diseased turf. However, wind and cool, moist temperatures are the biggest culprit in spreading this disease. Invasion by the fungus is very quick, and leaves may begin to die within 2 days after becoming infected. Dried pieces of the fragmented "red thread" enable the fungus to survive when conditions are not favorable for disease development (winter, mid-summer, etc.). During dry conditions, the "threads" may live for up to 2 years.

Treatment Options

Maintain adequate soil fertility. The actual fertilization rates will depend upon the types of grass(es) grown, soil texture, and the specific rates recommended in your area. Maintain a soil pH of 6.5 to 7.0.

Avoid overwatering. Do not water the lawn in the late afternoon or evening. Provide good soil drainage. Plant trees and shrubs far enough apart so that large areas of grass do not remain shaded for long periods during the day and so that dew and other moisture on the grass will readily evaporate. Selective pruning of established trees and shrubs may also help.

Do not allow thatch levels to become excessive. As I said earlier, correction of this disease is very easy and does not need any fungicidal treatments! Start your iron treatments before the cool, moist, fall temperatures start happening (usually around mid-November) and follow again every 6 to 8 weeks until warmer temperatures (75 degrees plus) occur. The iron will darken your lawn without the heavy growth rate that you’ll see with a nitrogen based fertilizer and you will not need to mow at all! You'll be amazed how dark green it will be and just how long it will stay that way (usually up to eight weeks!). The iron will also kill any moss present in your lawn. Always include iron with your normal fertilizing program during throughout the year.

BE CAREFUL NOT TO ALLOW THE IRON TO COME IN CONTACT WITH WOOD, CEMENT, BRICK OR ANY OTHER MATERIAL. IT WILL PERMANENTLY STAIN!

Meanwhile, back at the farm...