Summer Patch Resistant Kentucky Bluegrass

Summer Patch Disease

• Summer patch disease can kill Kentucky bluegrass, so you should use resistant cultivars. The fungus Magnaporthe poae causes summer patch disease in humid weather when daytime temperatures are between 70 and 100 degrees Fahrenheit and the nighttime temperature is about 70 degrees F. Symptoms include 2- to 3-foot-wide circular patches of dead grass with apparently healthy grass in the center. The patches increase in size and blend together, and dark brown or reddish dry rot spreads through the crown and roots.

Compact America Type

• Compact type Kentucky bluegrass cultivars have a compact, low growth habit and may spread aggressively. The America subtype resists summer patch disease and includes “America” and “Sonoma” cultivars. These fine-textured cultivars have a bright, dark green color and high density, and resist summer patch disease even with a close mowing height between 1/2 and 3/4 inch high. America type cultivars tolerate medium shade and drought and quickly recover from summer heat stress.

CELA Type

• CELA cultivars make up a subtype of the winter and spring type Kentucky bluegrass cultivars. The CELA subtype resists summer patch disease and includes “Challenger,” “Eclipse,” "Liberty" and “Adelphi.” These Kentucky Bluegrass cultivars have medium density and medium texture, and keep their vigor and color in cooler temperatures. Green-up occurs in late winter or early spring, and the grass appears less stemmy than the Bellevue subtype of spring and winter Kentucky bluegrass.

Other Types

• Other summer patch-resistant Kentucky bluegrass cultivars include “Monopoly” and “Baron.” Like other Mid-Atlantic type cultivars, “Monopoly” is a vigorous turf grass with deep, extensive roots and early spring green-up. Its tendency to recover from summer heat helps it resist summer patch disease, which is active in hot, humid weather. “Baron” is a BVMG type of Kentucky bluegrass. This medium-texture type resists summer patch disease, but has a stemmy appearance and unreliable performance in winter.