Horticulture Hotline 02/03/20
By Bill Lamson-Scribner
While walking and driving around it seems that brown patch/
large patch/ Zoysia patch has invaded the Lowcountry. As the cooler weather
comes and the grass growth rate slows down, large patch / brown patch / zoysia
patch fungus will begin to show up in our lawns. This disease is always present
in the lawn, it just manifests itself when the environmental conditions are right
and your grass cannot outgrow the damage. Without any sustained cold
temperatures, this disease is slowly spreading across lawns as the temperatures
that favor its growth keep coming into play. Our temperatures keep creeping
into the high 60’s even though it is winter. Brown patch loves temperatures in
the 60”s.
Since this disease is a big problem in the Lowcountry,
knowing that it is a soil borne disease can help you with control
strategies. Being a soil borne disease,
you know that it will reoccur in the same areas year after year. There are not any spores flying through the
air like many of your leaf spot fungi, so the disease is easier to control.
As a soil borne fungus, if you map the areas that you have
the disease, you can concentrate your control efforts (dollars) into a smaller
area, putting less control products into the environment. If your yard is 5,000 sq ft usually you might
have a few infected areas which might total approx. 500 ft. Instead of buying control products to treat
5,000 sq ft, you can concentrate your efforts into the 500 ft (i.e. 10% of your
total yard). If Large Patch was an air
borne fungus with spores, you would have to treat the entire yard because air
borne fungi spreads a lot quicker than soil borne fungi.
As your grass is going into dormancy and the temperatures begin
to cool at night, large patch is ready to attack your grass. Large patch will
go inactive when the temperatures get very cold; however, it will become active
again when the temperatures favor the disease. If you have discolored areas in
your yard that appear to be a disease, check with someone that knows. Even if
it is during a cold phase and the disease does not appear to be active, you can
still put out a systemic fungicide for protection. Our soils do not get so cold
that the plant will not absorb the fungicide with its roots. Remember treating
a fungus with a systemic fungicide is like getting a flu shot – you do it preventatively
before you have the disease. In this case, when you want the disease to stop
spreading.
A good granular
one-two punch control strategy is T-Methyl and Strobe Pro G (all systemic
fungicides that get into the plant). Use
these products in areas where you have had Large Patch previously at the
preventive rates and intervals recommended on the labels. Be sure to use
T-Methyl with Strobe Pro G, so you are switching chemistry classes and modes of
action. Good control early on can help avoid flare ups in the spring also.
Large patch usually likes wet, heavy thatch, improper
nutrition, and/or compacted soils.
Culturally you need to manage your irrigation system, raise any low
areas, and correct drainage problems.
Reducing thatch (at Possum’s we have a great organic granular product
for controlling thatch), maintaining proper fertility levels, and aerating to
alleviate compaction, will also help control large patch. A healthy turf
(following soil test derived feeding schedule) with a soil with a lot of
bio-diversity (use of cotton burr compost, SeaHume and other organics) has
shown to help manage this disease.
Always read, understand and follow product label. The
product label is a Federal Law.
