Lawn Fungus


Lawn Fungicide

Preventing, Killing Fungus in Lawns

Fungicide Prevention of Fungus       Non-chemical Prevention of Fungus

Plant Disease Products    Lawn Pests    Lawn Fungus: Dormant or Active?

Most lawn fungus problems can be prevented by a combination of proper maintenance and the use of a good fungicide.  Both methods of preventing fungi growth in lawns are important.

Non-chemical Prevention of Fungus

A healthy lawn (like most plant life) is able to fight off enemies such as fungi, weeds, soil and insect pests.  Keeping your turf grass cut at the correct height and applying water at proper times will go a long way in fighting off lawn pests.  Most plant diseases thrive under certain conditions that include moisture and temperature.  That is why you will notice brown patch, dollar spot and other diseases appear during certain seasons.  This also means that you should not make matters worse by improper mowing, watering or application of fertilizers (especially high nitrogen weed and feed products.)
Watering at night is one of the practices that should be avoided.  Start your lawn watering in early morning hours.  This will give your grass better drying times.  The practice of watering turf grass just a little amount every day should also be avoided.  This only creates weak surface roots (and a weaker plant that cannot fight off lawn pests) and keeps your turf wet too often – begging a potential lawn fungus to attack the grass.  Proper watering of your particular type of lawn in your area can be discussed with your local county extension office.
Fertilizer applications cause as many problems as do poor watering and mowing practices.  A lawn or turf fungus will thrive on the extra nitrogen provided by certain fertilizers – especially  weed & feed products that contain 18-0-18 or similar formulations.  The first number in the analysis (18) represents nitrogen.  Never use such a fertilizer until the proper time of year for your area.  This timing varies from zone to zone; contact your local county extension office to get this information.  These high nitrogen products are not bad products, but they can be used at bad times of the year, used too often and applied at rates that are too high.
Beware of lawn and garden centers that push you into using a high nitrogen weed & feed product too early in the year!  If applied too soon, you are “pushing” a dormant grass with high nitrogen before the grass is ready to grow.  This bad practice will many times lead to fungus problems and turf grass that gets hit with a late freeze.
A grass (especially turf grass) is at its most vulnerable state when upper plant growth is pushed by applied nitrogen.  If your lawn tends to have fungus problems (even with good watering and mowing practices) you should use a turf fungicide at lower levels at the same time you apply a high nitrogen content fertilizer.
If you need a weed prevention program, try using a pre-emergent herbicide and follow-up with a weed and feed later on when your lawn is not so vulnerable and is ready to grow.  Another excellent product is Pre-M granular fertilizer.  This product has a 5-10-20 analysis and contains a pre-emergent herbicide that kills seeds as they are trying to germinate.
Most people will misdiagnose their lawn problems in late winter to early spring.  As their lawn begins to wake up from its winter dormant stage, scars from the previous year’s problems give the appearance of active fungus, molecricket or other pests.  A good way to find out if your damage is due to previous or current problems is to mark the spots with small sticks, turf paint or other such materials.  Check the size of the areas for several days.  If the damaged areas do not become larger (especially as your lawn is just beginning to green up) then you are probably looking at damage from a previous infestation of some sort of lawn pest.  If the circles or patches spread out or get larger, you could be seeing an active infestation.

Fungicide Prevention of Fungus

Fungicides were invented to prevent certain fungi from attacking plants.  Once you have a fungus problem, fungicides have to be applied at higher rates and often have to be applied more than once at the high rate.  Using a fungicide as a preventative tool will save you money, time and maybe your lawn!

Daconil is no longer listed for use on lawns.
There are certain times of year that you probably have noticed fungus or disease attacking your lawn.  This year, beat the problem to the punch by applying your fungicide just before lawn problems begin.
One of the best fungicides to use is Eagle F-Stop.  This is a systemic product that lasts longer than topical treatments.
The best time to use fungicides is when you make your first yearly application of fertilizer, especially weed and feed products or others with high nitrogen content.  Since grasses are most vulnerable as they are being pushed by nitrogen, this is a perfect time to use fungicides at preventative rates.


  • Help your lawn to help itself!  Mow and water your lawn properly.
  • Choose your fertilizer wisely; do not apply too much nitrogen and time your fertilizer application so as not to encourage fungus problems.
  • Use a good systemic fungicide as a preventative tool.  Do not wait until you have a problem.  Combining your systemic fungicide with your weed and feed application is good.
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