Rust Turns Lawns Orange
Rust appears as an orange or yellowish-orange powder (spores)
grass leaf blades, especially in late summer to early fall when
the weather is dry. Rust typically develops on lawns and other
turf areas growing very slowly. Overall, the turf may assume a
yellow, red, or brown appearance. Close examination will reveal
the pustules, which easily rub off on your hand. Rust spores can
easily be tracked into homes.
Orangish rust spores are visible on leaf blades of a grass
Low fertility (in particular nitrogen) and low water availability
slow down turf growth, allowing rust to develop. Seasons with
excess rain may have rust outbreaks due to depletion of available
nitrogen. Cool nights with heavy dew and light, frequent rainfall
add to the ideal conditions for rust to develop. Warm, cloudy,
humid weather followed by hot, sunny weather also favors rust
development. Kentucky bluegrass, perennial ryegrass, and tall
fescue are all affected, depending on cultivars. Rust spreads
via air, water, shoes, equipment, and vegetative turf material
(sod). Rust may weaken turfgrasses and make them more susceptible
to other problems.
Control rust through sound turf management. Begin by choosing
a quality turfgrass seed blend of several cultivars of the species
desired for the site. Resistance to rust can vary according to
the race of the disease present. A diverse turf stand helps combat
rust and numerous other turf problems. Maintain lawns through
sound watering, mowing, and fertilizing. Water early in the day
so the grass dries quickly. Manage problem thatch. Increase vigor
with an early fall nitrogen application, but don't overdo it.
Check soil phosphorus and potassium levels through soil testing.
Also assure good airflow over the site and light penetration by
pruning trees and shrubs in the area near the lawn.
When rust occurs in late summer, improved growth conditions of
early fall often get lawns growing more vigorously and the rust
fades away. Early September is a key time for fertilization. If
conditions are dry, irrigation is also needed to increase the
growth rate of the grass.
Fungicides are rarely suggested on home lawns for rust control.
Focus on cultural practices described above.
Written by Bruce Spangenberg, former Extension
Educator, Horticulture. University of Illinois Extension.