Diseases ›

Slime Mold

Symptoms

Many small, round pustules are observed on the turfgrass leaves in small patches. The patches develop very quickly, usually overnight. The pustules may be purple, white, gray, yellow, or orange in color. The slime mold organisms do not infect the turf or cause direct harm, but they can cause mild yellowing of the leaves due to their shading effect. Slime molds are unsightly but are not considered harmful.

Development Factors

Slime mold spores survive in the soil and thatch. During warm, wet weather the spores germinate and develop into a slimy mass that grows over the soil and nearby plant parts during wet weather. The pustules observed on turfgrass leaves are reproductive structures that contain numerous spores.

Flushes of slime mold growth are often observed after heavy rain storms that were preceded by long periods of dry weather.

Cultural Control

Slime mold pustules typically disappear after 2 to 3 days; therefore, no control practices are needed. If the growth is particularly unsightly, the pustules may be removed by brushing, mowing, or washing the turf.

Chemical Control

Fungicides are available for slime mold control but are only necessary in severe cases.

Fungicide and Formulation1
Amount of Formulation2
Application Interval3
Efficacy Rating
Resistance Risk
Fungicide and Formulation1

mancozeb (Fore)*

Amount of Formulation2

4 to 8

Application Interval3

7 to 14

Efficacy Rating

+++

Resistance Risk

Low

1 Other trade names with the same active ingredients are labeled for use on turfgrasses and can be used according to label directions.
2 Apply fungicides in 2 to 5 gallons of water per 1,000 square feet according to label directions. Use lower rates for preventive and higher rates for curative applications.
3 Use shorter intervals when conditions are very favorable for disease.
* Products marked with an asterisk are not labeled for home lawn use.

Efficacy Rating
++++ = excellent control when conditions are highly favorable for disease development
+++ = good control when disease pressure is high, excellent control when disease pressure is moderate
++ = good control when disease pressure is moderate, excellent control when disease pressure is low
+ = good control when disease pressure is low
? = not rated due to insufficient data

Resistance Risk
Low = Rotate to different chemical class after 3-4 applications; tank mixing not necessary
Medium = Rotate to different chemical class after 1-2 applications; tank-mixing with low or medium risk product recommended
High = Rotate to different chemical class after EVERY application; tank-mix with low or medium risk product for EVERY application
? = not rated due to insufficient data

Presentations

Publications

Species Data

Host species

all

Months with symptoms

April to September

Stand symptoms

spots, patches (4 to 12 inches)

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Foliar symptoms location/shape

no distinct leaf symptoms

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Foliar symptoms color

all

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Root/Crown symptoms

none

Fungal Signs

pustules

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