Millipedes

After adding slug and snail bait to my Napa cabbage patch more times than I thought I should have to, I took a closer look and discovered a “new” pest in my garden: millipedes.

Greenhouse millipede (Matt Reinhold) CC BY-SA 2.0

Now, millipedes have been around for over four hundred million years, making them one of the oldest land animals. Lucky for us, those prehistoric millipedes are no longer around, since some of them were over SIX AND A HALF FEET LONG! Yikes! Thank goodness that our little garden millipedes are profoundly smaller!

Millipede description

Despite their name, which means thousand legs, none of them have that many. Most varieties have 30 to 90 pairs of legs. Millipedes have antennae with seven segments. Most millipedes are brown or black, but there are orange and red species.

Millipedes vs. centipedes

Unlike centipedes, which are carnivores, millipedes are vegetarians. While both have segmented bodies, centipedes have one pair of legs per segment, while millipedes have two. Millipedes are decidedly slower than centipedes, but they can devastate young seedlings (and Napa cabbage). While centipede bodies tend to be flat, millipedes are more cylindrical. It’s probably not a good idea to handle millipedes (although some people raise larger varieties as pets), since many of the 12 to 80 thousand varieties secrete defensive chemicals when threatened.

Millipede diet & lifecycle

Millipedes prefer burrowing in dark, damp areas, so it’s no surprise I haven’t seen them. They lay eggs and overwinter in the soil. Garden centipedes are usually only 1/2 an inch long, though they can reach over 6 inches. Surprisingly, millipedes can live for several years. In addition to eating vegetation, millipedes are known as detritivores, which means they eat dead stuff that’s mostly plants and poop. There are a few omnivorous and carnivorous millipedes, but they are no problem in the garden. When a garden millipede is disturbed, it will curl up into a coil. Here in California, we have three species of garden millipede:

• common brown millipede (Diploiulus luscus)
• imported greenhouse millipede (Oxidus gracilis or Orthomorpha gracilis, depending on which scientist you ask)
• bulb millipede (Nopoiulus minutus)

​Millipede control

Chemical controls, such as pesticides, are not effective against millipedes. The best way to cut millipede populations in your garden is to reduce moisture levels and increase air flow. My millipede problem has been occurring in a raised bed that contains large, feathery fennel, broad leafed rutabagas and, yep, you guessed it, Napa cabbage. Apparently, the other plants are holding all that precious water just as I had hoped, never realizing that I would be creating the perfect habitat for a pest that would skeletonize all of my Napa cabbage plants. So, here’’s the list of tips for reducing our millipede populations:

• Keep lawns mowed short
• Dethatch lawns
• Remove debris
• Keep compost piles away from growing areas
• Allow soil to dry out between waterings
• Space plants to allow for better airflow

Weird notes on millipedes: the study of millipedes is called diplopodology and the people who do the studying are called diplopodologists. Also, Venezuelan Capuchin monkeys rub themselves with millipedes because those defensive secretions are a natural mosquito repellant, which prevents freeloading bot fly eggs from hatching and embedding themselves in the monkeys’ skin.  Don’t care - not doing it.