You Are Here: Management Updates 2007 Archive April 23, 2007

Date: April 23, 2007
Category: Diseases
Subject: Red Thread

The question of season long persistence of Red Thread caused by a fungus (Laetisaria fuciformis) and its poor response to fertility adjustments has been raised by lawn care professionals. Usually, Red Thread is not a serious problem on intensely managed turf (golf courses). However, the disease can be problematic in residential turf as the turfgrass species, perennial ryegrass and fine fescue, are more susceptible

There are two reasons in recent years why Red Thread is becoming a more serious problem for landscapers: 1) climate conditions and 2) poor cultural practices or growing conditions for turf. We had cool and wet weather this spring and last fall as well as a prolonged period of surface moisture on or at snowmelt. Unusually heavy precipitation in early spring this year represents a trend toward an increase in the frequency of extreme rain events (> 2 in/48 hr). Such events result in more soil compaction and plants become more vulnerable to disease problems caused by wet conditions. Red Thread, in particular, thrives on prolonged cloudy, drizzling weather.

One of the best cultural practices to manage red thread is to provide the proper nitrogen fertility level; this is not as simple as throwing a little fertilizer at the problem. Maintain adequate and complete (potassium, phosphorous, calcium as well as nitrogen) fertility as determined by soil tests (web site: http://www.umass.edu/plsoils/soiltest ).

Other cultural practices include:

• Apply water-soluble sources of nitrogen to reduce disease severity.
• Maintain a soil pH between 6.0 and 6.5.
• Water deeply and infrequently.
• Avoid late afternoon, evening, and light, frequent irrigations which extend periods of leaf wetness
• Prune trees and shrubs to improve air circulation and increase light penetration.
• Keep mower blades to sharp to minimize leaf wounding which can enhance infection.
• Collect grass clippings when the disease is active or growing slowly to reduce the number of sclerotia that are incorporated into the thatch.
• Despite limited information on cultivars susceptibility to Red Thread, the National Turfgrass Evaluation Program (NTEP) (web site: http://www.ntep.org ) provides a list of perennial ryegrass cultivars’ susceptibility to Red Thread.

Submitted by: M. Bess Dicklow, Dr. Geunhwa Jung

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. The author and the University of Massachusetts are not liable for any consequences of any pesticide "recommendations". Mention of any trade name is not to be considered endorsement of a product.

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