What is powdery mildew?

This lawn disease is a parasitic form of a plant life called fungi. Fungi live in the soil, thatch and dead leaves all year round and feed by drawing nutrients from the grass.

Powdery Mildew is a damaging disease of bluegrasses and fescues. Periods of low light intensity and poor air circulation favour the disease. Heavily shaded areas are particularly susceptible. The disease is most severe during the spring and fall at temperatures between 15-22ºC. However, under the right conditions it can occur at temperatures ranging from 1-30ºC.

How can I tell if I have powdery mildew in my lawn?

The symptoms of powdery mildew include the following:

  • Early stages of Powdery Mildew are recognized as isolated colonies of whitish fungal structures called mycelia appearing on the leaf blades

  • The mycelia colonize and infect a large portion of the leaf blade with a whitish, grey dusty powder

  • Older leaves are more severely infected than younger leaves

  • Heavily infected leaves can turn yellow then brown and die. Colonies of powdery mildew darken with age

  • Infected plants are weakened becoming more susceptible to other stresses

If you are not sure if you have Powdery Mildew, call your local Weed Man Professional for a free healthy lawn analysis. They will diagnose the problem and advise on the proper corrective measures.

How can powdery mildew be treated?

The best treatment for Powdery Mildew is to alter some cultural practices that are causing favourable conditions for this disease to spread. As long as conditions remain favourable Powdery Mildew will continue to infect the grass blades and over extended periods of time will start to cause permanent damage. These cultural practices include;

  • Increase air circulation and light penetration through pruning and thinning trees and shrubs

  • Over seed lawn areas with a shade tolerant grass seed

  • Raise mowing height making sure it is being cut at 6 to 8 cm

  • Water deeply and infrequently to avoid drought stress

  • Improve drainage to increase water absorption to the root zone and increase air circulation. Lawn core aeration will assist in accomplishing this

  • Do not water at night. Water laying on grass plants overnight encourages the disease to spread

  • Provide adequate fertility while avoiding excessive nitrogen that can contribute to the disease. A slow release granular fertilizer[link] like Weed Man's exclusive blend will provide nitrogen over an extended period of time

If you have any further questions about Powdery Mildew in your lawn or have any other questions or concerns, please feel free to contact your local Weed Man Professional.