Hosts Most grass species are susceptible.
Cause Spores of the fungus-like organism Sclerophthora macrospora move via free water. The disease usually is associated with poorly drained or overwatered areas.
Symptoms The turf yellows in a diffuse pattern. Infected plants may exhibit mottled leaf blades, which eventually yellow and senesce. Occasionally, reddish spots may be seen on infected leaf blades. "Yellow tuft" symptoms are not common in the Pacific Northwest. Under a microscope, oospores may be seen in leaf blades.
Cultural control
- Improve drainage.
- Provide adequate, balanced fertilization.
Chemical control To prevent developing resistant fungi, alternate or tank-mix materials from different groups with different modes of action.
- Chipco Signature at 4 to 8 oz/1,000 sq ft. Group P7 fungicide. 48-hr reentry.
- Fosphite at 2 to 3 fl oz/1,000 sq ft. Do not use copper products within 20 days of treatment and do not use spray adjuvants. Do not mow or irrigate until sprays dry. Group P7 fungicide. 4-hr reentry.
- Heritage (4-hr reentry) and Compass (12-hr reentry) are labeled for turf, have activity on many other downy mildews and may be useful here. Group 11 fungicides.
- Mefenoxam 2 AQ at 0.49 to 0.98 fl oz in 1 to 5 gal water per 1,000 sq ft. Tank-mix with another fungicide such as mancozeb. Group 4 fungicide. 48-hr reentry.
- Phostrol at 8 fl oz/1,000 sq ft. Group P7 fungicide. 4-hr reentry.
- Subdue MAXX at 0.5 to 1 fl oz/1,000 sq ft. Tank-mix with another fungicide such as mancozeb. Group 4 fungicide. 48-hr reentry.
Combination Fungicides
- Honor at 0.55 to 1.1 oz/1,000 sq ft. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. Golf course turf only.
- Lexicon at 0.34 to 0.47 fl oz/1,000 sq ft. Group 7 + 11 fungicide. 12-hr reentry.
- Navicon at 0.7 to 0.85 fl oz/1,000 sq ft. Group 3 + 11 fungicide. 12-hr reentry.
- Pillar G at 3 lb/1,000 sq ft. Group 3 + 11 fungicide. 12-hr reentry.
Reference Wilkinson, H.T. and Pedersen, D. 1993. Yellow tuft of Kentucky bluegrass sod identified in Illinois. Plant Disease Notes 77:647.