You Are Here: Management Updates 2008 Archive July 21, 2008

Date: July 21, 2008
Category: Diseases
Subject: Yellow Spot

New turfgrass disease: Yellow Spot
Yellow spot appears in the form of yellow, chlorotic, circular discrete patches ranging from dime/quarter size up to 2-3 inches diameter on bentgrass putting greens, tees and approaches. The disease does not destroy the plant in any structural capacity; however yellow spot does reduce the aesthetic quality of turfgrass.  The primary causal agent of the disease is not fully understood but has been suggested to be cyanobacteria causing blue-green algae.  Do not confuse Yellow Spot with Yellow Tuft which is caused by Sclerophthora macrospora (see pictures).

Yellow Spot has been reported on creeping bentgrass putting greens on golf courses in the southeastern region of United States.  However, in 2007 yellow spot was reported on a few golf courses in Eastern Massachusetts.  As early as last week the disease appeared on creeping bentgrass putting greens and colonial bentgrass tees on golf courses in the Boston area.  High humidity and temperatures (>90° F day and >65° F night) are main triggers.  It is believed that many more golf courses with sand-based greens in the New England region may have experienced yellow spot.  However, superintendents may be hesitant to report the disease because it does not cause rapid thinning or death of plants, but it is detrimental to appearance.

If you see Yellow Spot this year, then the disease is likely come back to the same greens again next year unless preventative applications with contact fungicides such as chlorothanonil (Daconil Ultrex™) or mancozeb (Fore Rainshield™) are made before symptoms appear.  Once the symptoms do appear, it is very difficult to manage the disease and adequate control my require several applications.

Since Yellow Spot may be associated with algae, any cultural practices that increase air circulation and decrease shade around greens will be helpful.  Also, increasing surface drying by frequent topdressing in addition to light spiking, and reducing compaction, should be helpful as well.  If your tolerance level to this aesthetic disease is high, then wait until Mother Nature (cooler day and night temperatures) takes care of it, but the time frame for symptoms may extend into the fall.

This week a research plot will be set up at a golf course in the Boston area to begin testing products.

http://www.umass.edu/agland/diagnostics

Yellow Spot		Yellow Tuft

Submitted by: 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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