Horticulture Hotline 01/23/2017
By Bill Lamson-Scribner
The basically warm, high humidity winter has finally made
fungus explode throughout the Lowcountry. I don’t like to cause panic. We have
only sent out one email alert in 14 years from our stores. (If you would like
to get on our email list, stop by any of our 3 Possum Landscape and Pest
Control Supply stores to sign up.) The rains of 2015 and 2016 (Matthew) really spread
the fungus to new levels. These new areas of infection are showing up now with
the perfect environmental conditions and are likely to show up again this
spring. Be ready. Fungicides work like the flu shot – they are best to be used
preventatively before you have the disease. Unlike the flu shot, if you don’t
get it out in time, there are curative rates you can use.
Large Patch or Brown Patch fungus loves these weather
conditions. Temperatures at night in the high 50’s to low 60’s and moisture
make conditions real favorable for Large Patch or Brown Patch fungus. We have
had plenty of these conditions making the fungus environment perfect for the
spread of this disease. Fog, rain, no sun (Saturday I heard someone blame the
weather on Trump) and the perfect temperatures has caused disease on areas I
have never seen disease before. With these weather conditions, you see those
round, yellow areas of disease. Or sometimes the whole yard is covered in
disease. Walk through your neighborhood, you will see what I mean.
Since it is very difficult to control night time
temperatures and humidity, you can put your efforts into doing other cultural
things to help minimize the disease. Large Patch or Brown Patch fungus 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 (now or when the grass is
growing - BGK 7500, when grass is growing - aeration or dethatching),
maintaining proper fertility levels via soil testing, and aerating to alleviate
compaction, will also help control Large Patch or Brown Patch fungus.
Certain organic products have shown to increase
microorganisms in the soil that compete with plant pathogenic fungus in the soil.
At Possum’s we get good feedback from Nature’s Blend, SeaHume, Crab Shell, Corn
Gluten, Cotton Burr Compost, and some of the Roots products. These products are
not fungicides; however, people that use them report back to us that they
notice less fungus in the yards that they apply these products. Coincidence or
real science? I’m thinking real science because I have noticed it in my yard
too. Try some of these products in areas that you know you get the disease, and
see how it works for you.
Since the grass is semi-dormant, a systemic control product
like T-Methyl or Fame might be a good idea to get you through the next month or
so as long as conditions are favorable for the disease. Be careful because some
of the fungicides in the SI or DMI class (Bayleton) of chemistry slow down the
growth of the grass making the grass more susceptible to fungus. Actively
growing grass will recover faster from disease.
Being a soil borne disease, you know that it will reoccur in
the same areas year after year. If the
base of a leaf blade with Large Patch is moved from one part of the yard to
another (lawn mower – not real likely if you have sharp blades), this can begin
a new infection area; however, these are not spores flying through the
air. 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 had to treat the entire
yard because air borne fungus spreads a lot quicker than soil borne fungus.
Always read, understand and follow product label. The
product label is a Federal Law.
