Powdery Mildew

Disease

Blumeria graminis


Turf affected by the disease have a grayish white cast, with initial symptoms appearing as white patches on the leaf blade. Eventually the whole leaf blade becomes covered by a white mass of spores. Leaves begin to deteriorate, turn yellow, and eventually die, and brown to black fungal structures (cleistothecia) may be seen.

The pathogen can overwinter via specialized structures, and germinates in the spring of the year infecting turf in the late spring or early summer. Secondary spore production on leaves serve to re-infect new grass plants throughout the season. The pathogen is favored by cool cloudy conditions and high humidity. The disease also only occurs in turf located in areas where sunlight is at a minimum due to shade.

  • Crops Affected: Turfgrass

    Damage

    The location of this disease is home lawns and golf courses. General and foliar symptoms are dusty. This can occur during the months of April, May, June, July, August, September, and October. Hosts of the disease are Kentucky Bluegrass, Perennial Ryegrass, Fine Fescue, Annual Bluegrass, and fine-leaf fescues.

    Management

    Increasing the sunlight to the affected area will alleviate the problem. Unfortunately, cutting down trees, or removing a building is usually not an option. However, pruning low branches of trees can aide in air circulation and potentially increase light. Planting a less susceptible cultivar such as a shade tolerant Kentucky bluegrass, perennial ryegrass, or annual bluegrass could also be an option.

    Chemical management of powdery mildew can be accomplished with the DMI and QoI fungicides. However, the pathogen can develop resistance rather rapidly, and there are very few instances where the cost of fungicide application would be advisable.