Simple techniques eradicate slime mold

The mild days of spring are slowly giving way to the heat of summer.

And with this transition comes an increase in insects, disease and other pests. One of the more interesting and colorful organisms that are likely to be found this time of year are slime molds. These blue, gray, yellow or orange masses of “goo” can appear overnight in your lawn or garden. Do not worry, however, as there is a reasonable explanation for their occurrence. Here are some tips to help you deal with these early summer guests.

Slime molds are commonly found in turf, ornamental and garden plantings in the home landscape. Slime molds are primitive organisms that feed on bacteria, other fungi and dead organic matter. They often cause concern for homeowners because their reproductive phase is colorful and quite noticeable. On turf, large numbers of small gray, white or purple fruiting structures, called sporangia, form on the leaf blades during cool, humid weather. These fruiting structures range in size from small pinhead-size flecks to lumps a foot or more in diameter. Grass leaves within the patch can be dotted with the fine specks of the slime mold, or in some cases completely covered by the organism.

As these slime masses dry, they form unsightly bluish-gray, gray, black, white or yellow powdery structures. When crushed between the fingers, they disintegrate into a powdery mass that easily rubs free from the grass blade.

In mulch beds and other bare areas, large masses of orange, red, or yellow slime can be found. They, too, dry in a short period of time and simply fall apart.

Slime molds usually appear following heavy rains in spring and summer. They can also appear in well-watered and well-fertilized lawns and flower beds. Although unsightly, the slime molds do not harm living plants. Plant structures, such as leaves and stems, serve only as a means of support for the development of the slime mold fruiting structures. In the lawn, a heavy infestation of slime mold may cause a slight yellowing because it shades the grass blades.

Slime molds rarely, if ever, cause permanent damage to plants.

Chemical control of slime mold is not necessary. Frequent mowing, brushing with a broom or spraying with a steady stream of water does a good job of removing the fruiting structures. To prevent the occurrence of slime mold in the yard, remove excessive thatch or accumulations of organic matter regularly. Do this by core aerating the lawn each fall. In flowerbeds and other areas, apply fresh mulch yearly to keep beds looking nice. Do not, however, remove old layers of mulch as this can damage plant roots.

Bruce Chladny is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him at 843-7058 from 8 a.m. to 5 p.m. weekdays.