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Gray Leaf Spot

What is Gray Leaf Spot?

There are many microorganisms in your lawn which are beneficial, aiding in thatch decomposition. However, there are also a few harmful organisms that are parasitic form of plant life called fungi. Fungi live in soil, thatch and dead leaves within the lawn all year long. These fungi feed on the grass by drawing nutrients from the plant and destroying the plant cells. Diseases spread, in the form of spores, throughout your lawn by wind, air, water, and traffic. The disease may re-appear from year to year if certain conditions are favorable. As a general rule, areas that have been prone to disease problems in the past will at some time, if not yearly, have the same problems again.

Gray leaf spot is a warm season disease that affects primarily St. Augustine grass, Ryegrass and Tall fescue turf. Gray leaf spot is a fungus that survives as mycelium and spores on infected plant material. Spores are produced during hot humid weather and are then spread by wind, watering and mowing. Gray leaf spot starts out as lesions on the leaves and stems during warm humid weather. The lesions will grow larger with time with a tan appearance in the middle surrounded by a brown to purplish margin. Severely affected areas will thin out as the grass blades wither and die and turf will have a brownish appearance.


Gray Leaf Spot is most severe during prolonged rainy, humid, hot periods usually accruing in midsummer. Temperatures that are optimum for Gray Leaf Spot are between 80 to 90 degrees Fahrenheit (26-32*C). High nitrogen levels will favor the disease and any other factor that may stress the lawn such as improper mowing, watering, and soil conditions.


Weed Man's exclusive brand of slow release nitrogen feeds the plant as it needs it through the root. This will help ensure healthy turf without leading to problems later on. Watering properly is extremely important in this turf damaging disease. Avoid watering at night during hot humid weather which extends the leaf wetness period and can lead to a greater chance of Gray leaf spot disease. Allow for air movement and light penetration prune back any trees and undergrowth. Always keep a sharp mower blade as well as it will allow the turf blade tips to heal quickly.

Weed Man Milwaukee Can Help 

Your Milwaukee Weed Man dealer is here to help. Weed Man's turf specialists can recognize Gray leaf spot and make recommendations to help your lawn. Weed Man's specially blended slow release fertilizer applied at the right time is the first step in preventing Gray leaf spot. Weed Man's fertilizer helps create healthy turf by slowly feeding the lawn as it needs it encouraging deep rooting systems. Your Milwaukee Weed Man dealer will also be able advise you on any other treatments or cultural practices that may be necessary to help your turf remain healthy and vigorous.

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