Necrotic Ring Spot
Description:
Necrotic ring spot often appears two to three years after lawn establish-ment,
although it may not develop in a lawn for a decade or more.
Symptoms of NRS may be apparent throughout the growing season,
but they commonly intensify in late July or August during periods of summer stress.
Initially light green to straw-colored spots or patches several inches to several feet
in diameter develop in the lawn. The patches may be localized to one part of the yard
or widely scattered throughout the lawn. As the disease progresses, grass at the patch
margin begins to die and becomes matted whereas the grass inside the ring remains healthy
and green. This gives the patches more of a doughnut or frog eye pattern. Existing patches
from previous years often develop a bright yellow ring, followed by plant collapse and death.
Patches that develop in shady spots or areas with excessive thatch are more severely damaged
and have a crater-like appearance. In successive years, rings may coalesce to create larger arcs of dead turf.
NRS symptoms persist into early September but the turfgrass may recover during late fall and
the following spring to the point where the rings are no longer visible. However,
because of its perennial nature, NRS may reappear and intensify in mid-summer in successive years.
Control:
Necrotic ring spot continues to be a very difficult disease to manage because of its perennial
nature and inconsistency in control with fungicides. Nevertheless a combination of genetic,
cultural and chemical treatments can reduce NRS severity.
Prepare site before sodding or seeding.
Necrotic ring spot is more severe on sites with compacted soils and poor soil drainage.
Overseed diseased patches.
Do not overwater.
Avoid applying excessive amounts of nitrogen fertilizer.
Please check the "Extension Agents' Handbook of Insects, Plant Disease and Weed Control".
Click HERE for Kelly Solutions.
