Almost like clockwork (depending on environmental conditions), millipedes migrate in large numbers and become quite a nuisance for many homeowners. This is nothing new…Large migrations have been occurring for many years, according to Walter Ebeling, author of Urban Entomology. Some migrations were so large, it became necessary to apply sand on slippery railroad tracks for traction of locomotive drive wheels due to the squished millipedes. In 1919, a millipede migration caused cattle to stop grazing because of the high numbers on the pastures. During this time, large quantities of drowned millipedes were found in wells, rendering the water unsuitable for drinking for a while. Also, field workers became sick while hoeing a cornfield because the millipede population was so great the hydrogen cyanide odor from the crushed millipedes overwhelmed them. Ebeling goes on describing several other occurrences in his publication. You should check it out.
Florida currently has over 50 species of millipedes. The good news is, only a few of these migrate in large enough numbers to become a nuisance. In south Florida, the Yellow-Banded Millipede (Anadenobolus monilicornis) is known to exist in numbers high enough to cause homeowners grief. Although the Yellow-Banded Millipede is not a naturally occurring species, populations have grown quite large over the years. They’re often seen crawling over patios, sidewalks and up the sides of buildings. Monkeys in a Miami zoo have been seen rubbing these millipedes on their fur to help repel insects. They also feed on them, which makes them a little high… Silly monkeys! Researchers are still not sure as to how far north these may spread into Florida.
Another millipede that occasionally migrates, but seldom in numbers to cause any alarm, is the Florida Ivory Millipede (Chicobolus spinigerus). This millipede is often seen crossing roads and sidewalks. On occasion, they may invade patios, but rarely in high numbers.
There are two species of Flat-Backed Millipedes that migrate in extremely high numbers during the fall. The first is known as the Greenhouse Millipede (Oxidus gracilis) and the second is sometimes called the Cyanide Millipede (Asiomorpha coarctata) because of its ability to secrete hydrogen cyanide. Sounds nasty, doesn’t it? The two look very much alike and are almost indistinguishable.
Unlike the Yellow-Banded Millipede and Florida Ivory Millipede, the Flat-Backed Millipedes are much smaller, ranging from about ½” to 1” in length. The smaller size allows them to enter homes and businesses through cracks in thresholds, sliding glass doors, windows, etc. This migration usually takes place in late summer and fall (September through November).
Most millipedes feed on decaying organic matter, such as leaves and dead plants. The Cyanide Millipede enjoys feeding on thatch build-up in St. Augustine grass, where it also breeds. So, they are considered very beneficial for the environment. It’s not until they invade people’s homes they become undesirable… Go figure!
Controlling millipedes can be a challenge due to their behavior and high populations. Knowing a little about their biology and habits will help considerably. A thorough treatment of the grounds, including ornamental beds, is necessary. Our Smart Choice 4 for 3 program is an excellent program for controlling general lawn pests such as millipedes. However, in the case of millipede control, it is best that mulch be raked back to allow the control product to be applied where the millipedes are harboring. If the turf has heavy thatch build-up, aeration will help reduce the thatch, eliminating a major food source for the millipedes. If you’re seeing a myriad of millipedes, contact us for help!