Summer days and rusty nights
Rust is a common disease of turf in home lawns, and perennial ryegrass is especially susceptible.
It is actually a very complex organism! This disease is caused by a fungus which survives within the plant without killing the host plant.
Rust pathogens are recognized by the production of dusty orange spores, which look like rust on metal. Rust pathogens can produce up to five different kinds of spores, and may range in colour from yellowish-orange to blackish-brown. The good news is that it's not a deadly disease. Although unsightly, and the orange spores might brush off and ruin your white sneakers, the turfgrass will survive this attack.
In general, a good fertility program is always the start of a healthy turf system. Under-fertilized or deficient turf can be weak and more susceptible to common pests of this nature. Reducing leaf wetness periods will also help against diseases caused by fungi. This means mowing on mornings with heavy dew formation; you don't need to cut it, but at least run over it with the blade running at a high setting to knock off the dew.
Overseeding with less susceptible species, such as Kentucky bluegrass, could be an option if your have high percentage of perennial rye in your lawn. Removing, trimming, or moving trees and hedges that are blocking sun or air flow can also help to reduce leaf wetness duration. Research has shown that drought-stressed turf is highly susceptible to rusts, so you can use a sprinkler or irrigation system to restore turf health and reduce excessive dryness.
You can find more information in OMAFRA's Publication 845
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