Red Thread mycelium is red in color
of wet weather and temperatures of 65-75 degrees favor the
development of this common fungal disease.
While there is
not much you can do about the weather, you can keep the grass
mowed regularly so that it dries as soon as possible after rain.
If your lawn is shady, you might have an arborist thin out the
crowns of trees and limb them up a bit to allow more sun to
reach the grass, which also speeds drying after rain or dew. It
helps to keep your lawn mower blade sharp, too. The clean cut
from a sharp blade heals quickly, while the ragged blades of
grass left by a dull mower blade do not heal and provide an easy
entrance for disease-causing organisms.
Nitrogen Fertilization Helps!
Red thread can be
indicative of low nitrogen levels in a lawn. If you have not
fertilized your lawn by mid-May, an application of one pound of
nitrogen per thousand square feet can help reduce the severity
of red thread. Do not go overboard with nitrogen – more is not
better, and can open your lawn to much more serious and
destructive diseases when we get into hot, humid weather.
While of course
your neighbors’ lawns have experienced the same weather as
yours, the probable difference is the type of grass in your
yard. If perennial ryegrass or fine fescues are the predominate
species in your lawn, they are more severely injured by red
thread than Kentucky bluegrass and turf-type tall fescues.
3-Way Grass Mixture
Penn State Mix
is a combination of the three most common cool season grasses:
Kentucky bluegrass, perennial ryegrass and fine fescues. The
percentage of each species in the mix varies by supplier, but it
has a big impact on the species that predominate in the
resulting lawn. Perennial ryegrass is very aggressive and can
easily dominate Kentucky bluegrass if there is over 10 percent
perennial ryegrass in the seed mix. If your lawn is shady, the
fine fescues will predominate eventually. You may want to
overseed your existing lawn with a blend of Kentucky bluegrass
varieties to reduce the severity of red thread damage. Choose
those with shade tolerance such as Glade or Bensun if your lawn
Finally, the main
way to act on the causal organism is to apply a fungicide.
Fungicide applications for red thread are rarely warranted
in home lawns. You do not say what treatment was applied by your
lawn service, so it is difficult for me to comment. The best
course of action is to make sure the cultural conditions are as
correct as possible – proper mowing, allowing more sun to reach
the grass, proper fertility levels, and perhaps adjusting the
balance of grass species in the lawn. Fungicide applications
should be the very last resort. This can get expensive, because
applications should be repeated at intervals recommended by
fungicide labels as long as environmental conditions favor
disease development. Also, it is best to rotate among fungicides
with different modes of action to avoid developing resistant
strains of the causal organism.
VIDEO: Red Thread Disease