Millipedes and slime molds invading home lawns

By By Steve Strong / MSU Extension Service area agent
June 16, 2004
Summer is usually a favorite time for going barefoot and wiggling your toes in the lush green grass of your home lawn. But maybe not, after taking a closer look at some of the critters that are creeping and cropping up this year in St. Augustine lawns and flowerbeds alike.
Home landscapes are being invaded like the beaches of Normandy on D-Day, and the primary pest wiggling its way onto your porch and patio is probably millipedes. Millipedes, or the "little brown worms that crunch when you step on them" are actually Arthropod relatives of crayfish and centipedes, and all have a hardened outer shell covering called an exoskeleton.
Exoskeletons help protect Arthropods from predators, and that's what makes something like millipedes very hard to kill or repel. Like tiny armored earthworms (another distant relative), millipedes tunnel in the soil and feed on decayed organic matter such as leaf mold and landscape mulch.
Pesky creatures
These pesky creatures rely on a constant source of moisture to survive, and therefore are thriving with all the recent rains. Heavily shaded landscapes with plenty of well-mulched beds are the millipedes' preferred habitat, and abundant rainfall actually has them on the run looking for higher ground-like your house or even surrounding trees.
Liquid insecticides are available for partial control of millipedes (carbaryl or liquid Sevin for outdoor use only), or canned sprays can be used inside the home if they are labeled for indoor use. Dusts do not seem to be effective and will quickly wash away with the next rainfall, so the choices are limited. You'll probably have better luck praying for dry weather.
Wet soils and high humidity are producing another strange occurrence on home lawns around the area, in the form of colorful slime molds. Slime molds appear in early summer as black, blue or grayish streaks on the surfaces of lawn turf, and often look like some kind of weird "oil slick" was poured on the grass.
Upon closer inspection, however, homeowners find that the oily sheen is really a dust-like spore growth on the leaves that literally can be swept off like dry powder. Spore growth from slime molds generally occurs for only a few weeks before the fungus finishes its reproductive phase, disappearing again back into the ground until the start of the next growing season.
The good news is that slime molds are not a viable disease threat to the lawn grass (brown patch and take-all turf pathogens are another matter). It is often hard to convince someone who loves their lawn grass that the worst that slime mold spores can do is to shade the grass leaves enough to cause slight yellowing, and the easiest solution is a quick whisk with a broom or a leaf blower.
Fungicides
Fungicides labeled for lawn turf can be used to combat slime mold spore growth, but it seems like a silly waste of time and money for something that is nothing more than eyesore. Save the checkbook for the time when a real pest shows up that needs a dose of an approved pesticide.
Check with the county Extension Service office for more information on the variety of pest problems likely to plague your lawn and garden this summer. Also feel free to visit the MSU Web site at www.msucares.com, for free downloads of all of the publications that Extension has to offer.
Soil testing and disease diagnosis services are still just $6 per sample, and you may call 482-9764 for more details on sampling procedures. That's cheaper than the bag of fertilizer or the bottle of pesticide that most folks normally try to use to fix the problem, but it sure makes more sense to figure out what you're really dealing with first, before pumping up that spray tank.