Turf Wars: preventing fungal attack

Walking through the yard and your shoes become covered with an orange dust? Patches of orange powder found in the lawn? Rover turning red with residue? These are some of the recent calls received at the local ISU Extension Office lately.

The cause of these nuisance conditions is due to a fungal disease called “rust”. Largely cosmetic, this turf disease commonly occurs during late summer, creating rust-colored fungal spores that are easily dislodged from the grass leaf blade surface.

Fungal disease spores can be found in the soil of most every yard and garden in Iowa. But the good news is that before a fungal disease can develop and wage an attack on your grass, the right environmental conditions must first be present. Rust fungus thrives when temperatures are between 68 to 85 degrees and leaves stay wet for extended periods.

What to do? Rather than pull out chemical sprays, the first step to a healthy lawn is learning as much as possible about cultural requirements for the grass type being grown. Keeping a lawn healthy is the best plan to prevent a fungal attack on your turf.

Raising mowing height can help reduce stress on your grass. It is important to remember that the lower the mowing height, the greater stress to your grass. And the greater the stress, the more likely your yard will be subject to a fungal attack.

Lawns with insufficient nitrogen are more likely for a rust attack. Heavy rainfall and irrigation can leach nutrients from the soil. A small amount of N may be applied to problem rust spots. Avoid fertilizer extremes; use a slow released, well-balanced fertilizer as recommended by soil testing to help reduce disease.

An excessively high or low pH can also place stress on your lawn and increase the chance for fungal attack. A low soil pH may be a calling card for fungi to develop. Soil pH of a lawn should be tested regularly.

Other factors that affect susceptibility of grass to fungal disease include: poor drainage, compaction, and presence of trees or shrubs that reduce air circulation. Watering in the early morning or afternoon allows grass to dry and avoid fungal attack.

Did you know? Chemical fungicides are usually not needed to control rust, as winter dormancy will begin before the disease reaches damaging levels.

Have a gardening question? For ISU horticulture advice, email photos, along with a good description of the problem to Yvonne McCormick at yvonne@iastate.edu