Lawn and Turf-Pythium Crown and Root Rot

See:

Lawn and Turf - Damping-off

Cause Pythium spp. especially P. graminicola, fungal-like microorganisms favored by wet, flooded conditions. They survive unfavorable periods in soil and infected plant debris. Under favorable conditions, spores germinate and infect roots. After infection, the microorganism spreads mainly in the inner tissues of the roots. A thick-walled survival structure, oospores, are produced that can persist for several years. These organisms can be found in surface waters and survive through the irrigation system.

Symptoms Small patches or large turfgrass areas may appear thin, off-color, and slow growing. During cooler periods, such as early spring or late fall, symptoms may appear first as small, diffuse, yellow patches that coalesce into large yellow areas. During warmer summer periods, symptoms may appear first as small, tan, brown, or bronze patches of turf, which may converge to form large areas of wilted, dying turf.

Cultural control

• Water management is important in reducing disease potential. Provide good surface and subsurface drainage when establishing turf. Avoid overwatering and watering late in the day.
• Use only clean water for irrigation. Treat surface irrigation water to kill spores.
• Remove excessive thatch.
• Avoid excessive fertilization.
• Promoting vigorous root growth and reducing stress can help minimize severe damage.

Chemical control To prevent developing resistant fungi, alternate or tank-mix materials from different groups with different modes of action. Limit the use of any one group during crop production.

Products available in home packaging:

• Monterey Garden Phos at 5 to 10 fl oz/1,000 sp ft as a foliar spray. Group P7 fungicide. H

Products available for commercial use:

• Appear at 3 to 8 fl oz/1,000 sq ft. Group P7 fungicide. Reentry when sprays have dried.
• Banol at 1.3 to 4 fl oz/1,000 sq ft. Group 28 fungicide. 12-hr reentry.
• Chipco Signature at 4 to 8 oz/1,000 sq ft. Group P7 fungicide. 48-hr reentry.
• Disarm 480 SC 0.18 to 0.36 fl oz/1,000 sq ft. Group 11 fungicide. 12-hr reentry.
• Fame SC at 0.2 to 0.4 fl oz/1,000 sq ft. Group 11 fungicide. 12-hr reentry.
• Fiata Stressgard at 5 to 15 fl oz/1,000 sq ft. Do not mow or irrigate until sprays have dried. Do not use with foliar fertilizers of copper-based materials. Group P7 fungicide. 4-hr reentry.
• Heritage at 0.2 to 0.4 oz/1,000 sq ft. May increase this disease on tall fescue. Group 11 fungicide. 4-hr reentry.
• Mancozeb 80% (Fore, Manzate, and Protect DF) at 4 oz/1,000 sq ft. Group M3 fungicide. 24-hr reentry.
• Mefenoxam 2 AQ at 0.49 to 0.98 fl oz in 1 to 5 gal water per 1,000 sq ft. Do not use alone because resistant fungal populations can develop quickly. Group 4 fungicide. 48-hr reentry.
• OxiPhos at 8 to 12 fl oz/1,000 sq feet as a foliar spray. Group P7 fungicide. 4-hr reentry.
• Phostrol at 4 to 8 fl oz/1,000 sq ft. Group P7 fungicide. 4-hr reentry.
• Proplant at 3 to 4 fl oz/2 to 5 gal water/1,000 sq ft. Group 28 fungicide. 12-hr reentry.
• Segway SC at 0.45 to 0.9 fl oz/1,000 sq ft. Group 21 fungicide. 12-hr reentry.
• Subdue MAXX at 0.5 to 1 fl oz/1,000 sq ft plus another fungicide. Do not use alone because resistant fungal populations can develop quickly. Group 4 fungicide. 48-hr reentry.
• Terrazole L at 1.5 to 3 fl oz/1,000 sq ft. For tees and greens only. Group 14 fungicide. 12-hr reentry.
• Truban 30 WP at 4.5 oz/5 gal water/1,000 sq ft. Irrigate after application. Group 14 fungicide. 12-hr reentry.

Combination Fungicides

• Headway at 3 fl oz/1,000 sq ft. Do not use with silicone-based surfactants or EC formulations. Group 3 + 11 fungicide. 12-hr reentry.
• Heritage Action at 0.2 to 0.4 oz/1,000 sq ft. Group 11 + P1 fungicide. 12-hr reentry.
• Honor at 1.1 oz/1,000 sq ft. Irrigate lightly after application. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. Golf course turf only.
• Lexicon at 0.47 fl oz/1,000 sq ft. Group 7 + 11 fungicide. 12-hr reentry.
• Navicon at 0.85 fl oz/1,000 sq ft. Group 3 + 11 fungicide. 12-hr reentry.
• Pillar G at 3 lb/1,000 sq ft. Irrigate lightly after application. Group 3 + 11 fungicide. 12-hr reentry.
• Stellar at 1.2 fl oz/1,000 sq ft. Can only be used twice. Group 28 + 43 fungicide. 12-hr reentry.

Reference Cook, P.J., Landschoot, P.J., and Schlossberg, M.J. 2009. Inhibition of Pythium spp. and suppression of pythium blight of turfgrasses with phosphonate fungicides. Plant Disease 93:809-814.