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Rust Disease

Detection & Diagnosis

Rust on grass

Rust generally appears on lawns in late summer and fall when there are conditions of low light intensity and temperatures between 70-80ºF with high humidity. Alternating weather patterns with changes from cool, wet weather to hot, dry weather can also create suitable conditions for the disease. Rust survives on living and dead leaf tissue and in the thatch layer of turf grass. Only when weather conditions become suitable do they begin to cause a concern on the lawn. The disease also tends to be more severe in shaded areas.  

Most cool-season grasses are susceptible to rust, with perennial ryegrass being the most susceptible and Kentucky bluegrass being slightly less susceptible. The disease often appears in the form of yellowy-orange flecks on the leaves and tips of grass plants. The spots soon enlarge to form round pustules that rupture to release powdery spores. Because this powdery substance rubs off easily on clothing, shoes, pets, mowers and skin, it is usually fairly easy for homeowners to diagnose.

Conditions Favoring the Disease

There are several factors that play a role in the occurrence of rust disease:
- High humidity
- Nitrogen deficiency
- Low light intensity
- Prolonged lawn wetness (often from dew accumulation or watering at night)
- Overcast weather 
- Seasonal transitions from cool to hot or vice versa

Slow growing grass and areas of the lawn that are heavily shaded are often affected by rust.

Prevention and Control Tips

Rust can weaken lawn grasses and make them more susceptible to insect damage, weed infestation, and various other diseases. It can also cause permanent damage to the turf if left untreated for an extended period of time. It is best to contact your local Weed Man at the first sign of disease or any changes in the appearance of your lawn. 

Weed Man recommends the following care practices to eliminate or diminish the presence of rust disease:

- Provide proper fertilization to improve nitrogen levels in the lawn.

- Book a core aeration service with Weed Man. Aeration improves water penetration to the lawn’s root zone, helping push away disease spores from the turf.

- Increase mowing height and frequency. This will help stimulate turf growth. More growth means more mowing, keeping disease spores at bay. 

- Overseed any areas of the lawn that have been severely infected.

- Prune shrubbery and trees to allow more light to reach the surface of your lawn.

- Water in the early morning to reduce periods of leaf wetness. 


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