Yellow Patch

Symptoms and signs

Yellow patch, which sometimes is referred to as cool temperature brown patch, occurs primarily on bentgrass and annual bluegrass putting greens, but may occasionally be found on Kentucky bluegrass lawns.

On putting greens, this disease becomes visible when snow melts and appears as tan, brown, or yellow rings up to 600mm in diameter. The blighted turf usually is located around the periphery of the patch, leaving healthy appearing turf in the center. Damage from yellow patch usually is superficial, but significant turf loss can occur following prolonged snow cover or during prolonged cool and wet weather in early spring. Rings may appear on high cut turf as well, but rarely cause serious damage.

Disease Cycle

Rhizoctonia cerealis oversummers as dormant resting structures and begins disease-causing activities during cool, wet weather at temperatures of about 4°C. The disease frequently develops under prolonged snow cover, but does not require snow cover to produce symptoms. The fungus primarily attacks the leaf blades of turf, but can infect crowns and roots.

Cultural Control

Maintaining adequate levels of soil nutrients will help turf resist severe thinning by this disease. Improved surface and subsurface drainage will aid in reducing surface moisture that provides favorable conditions for disease development. Also, timely removal of winter greens covers will help surface drying and will reduce some disease incidence. Light applications of nitrogen fertilizer in the spring will quicken turf recovery from this disease.

Chemical Control

Preventative applications of broad spectrum fungicides in late fall and/or winter may help to reduce disease severity in winter or early spring.