Yellow tuft, or downy mildew, is caused by the water mold fungus Sclerophthora macrospora. The disease occurs on most turfgrass species, but is most common in creeping bentgrass or annual bluegrass putting greens. The disease is most damaging in areas that are poorly drained, over-irrigated, or have excessive thatch accumulations. Symptoms of yellow tuft appear in small, yellow spots that are scattered across the turf stand. On occasion, the spots may appear to follow drainage patterns. Closer examination reveals that the yellow spots are slightly raised above the turf canopy. The affected plants will pull easily from the turf to reveal dense clusters of yellowed tillers emanating from a single crown. This profuse tillering if referred to as a “witches’ broom” symptom, and is caused by production of hormones by the pathogen in the crown of infected plants.
Host Grass Species
bentgrass, bluegrasses, zoysiagrass
Month(s) with symptoms
April to September
Foliar Symptoms - Location/Shape
no distinct leaf symptoms
Foliar Symptoms - Color
Note: Still not sure if this is the right disease? The Turfgrass Disease Identification program may be helpful. Or consult the experts at the Turf Diagnostics Lab. Check the TurfFiles glossary for definitions of unfamiliar terms.
FACTORS AFFECTING DISEASE DEVELOPMENT
The yellow tuft pathogen is active during periods of cool, wet weather. The disease is most common in wet, poorly drained areas or where excessive irrigation is applied. The disease may occur in well-drained areas following periods of frequent rainfall.
Ensuring adequate surface and subsurface drainage is the most effective way to prevent yellow tuft problems. When constructing new turf areas, avoid establishing turf in low lying areas that will collect water and remain saturated for extended periods. If necessary, install subsurface drainage to carry water away from wet areas. Cultivate and topdress on a regular basis to reduce compaction, minimize thatch accumulation, and encourage rapid drainage.
Fungicides containing mefenoxam and metalaxyl are known to be very effective against yellow tuft. The effectiveness of other products is not well known. Curative control of yellow tuft is difficult, so a preventative fungicide program should be implemented in areas where the disease has been a persistent problem. Make applications on a 14 to 21 day interval during cool, wet conditions that are conducive to yellow tuft development.
Resistance Risk (2)
Fenox, Mefenoxam 2, Mefenoxam 2 AQ, Quell, Subdue
Autograph, Fosetyl-Al, Prodigy Signature, Signature
Alude, Magellan, Resyst, Vital, Vital Sign
3336, Fungo, Systec, T-Bird, T-Storm, Tee-Off, TM
chlorothalonil + thiophanate-methyl**
benzimidazole + nitrile
Spectro, ConSyst, Peregrine, Tee-1-Up, TM/C
pyraclostrobin + boscalid**
carboxamide + QoI
Fore, 4 Flowable Mancozeb, Dithane, Mancozeb DG, Pentathlon, Protect, Wingman
** Not for application to residential lawns.
excellent control when conditions are highly favorable for disease development
good control when disease pressure is high, or excellent control when disease pressure is moderate
good control when disease pressure is moderate, excellent control when disease pressure is low
good control when disease pressure is low
does not provide adequate control under any conditions
cannot be rated due to insufficient data
Rotating and tank-mixing not necessary, but recommended to avoid potential side effects from continuous use of same chemical class.
Rotate to different chemical class after 3-4 applications; tank-mixing not necessary.
Rotate to different chemical class after 2-3 applications; tank-mixing not necessary.
Rotate to different chemical class after 1-2 applications; tank-mixing not necessary.
Rotate to different chemical class after 1-2 applications; tank-mixing with low or moderate risk product recommended.
Rotate to different chemical class after EVERY application; tank-mix with low or moderate risk product for EVERY application.
Continual use of fungicides with similar control mechanisms (modes of action) can result in fungi that are resistant to some chemicals. Poor or ineffective disease control can be expected when this occurs. Managers can reduce the chances of this happening by mixing or alternating fungicides belonging to different chemical classes.
Recommendations of specific chemicals are based upon information on the manufacturer's label and performance in a limited number of trials. Because environmental conditions and methods of application may vary widely, performance of the chemical will not always conform to the safety and pest control standards indicated by experimental data. When more than one brand name exists for an agricultural chemical, the name of brand that first came onto the market is listed first. Otherwise, brand names are listed in alphabetical order. The order in which brand names are given is not an indication of a recommendation or criticism.
Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services does not imply endorsement by North Carolina State University or discrimination against similar products or services not mentioned. Other brand names may be labeled for use on turfgrasses. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county's Cooperative Extension agent.
© North Carolina State University. This information sheet was prepared by Lane P. Tredway, Gail G. Wilkerson, Bridget R. Lassiter, Jenifer J. Reynolds, and Gregory S. Buol. Departments of Plant Pathology and Crop Science, College of Agriculture & Life Sciences, North Carolina State University. Prepared March 7, 2011. Available on-line at www.turffiles.ncsu.edu. This publication was made possible through a grant provided by the Center for Turfgrass Environmental Research & Education (CENTERE) whose purpose is to support worthwhile projects that will benefit both the private sector and the public, and protect the environment.