The key here is “when they become a problem.” In general, pillbugs, or roly polies as I grew up calling them, are quite nice little composters.
The textbook “fact” is that pillbugs prefer to eat rotting organic matter and only graduate to other foods when they can’t find enough. That’s actually false. They’re opportunistic omnivores, and they’re going to eat the most nutritious thing available. In addition to rotting vegetation, their favorite foods include tender plant growth, fine roots, soft fruits, moist tubers, and new seedlings. In small numbers you’re unlikely to notice when a pillbug has taken a nibble, but when they overpopulate it turns into a major issue.
This morning I went to water the seed trays in our straw bale cold frame and discovered many of the trays were missing plants. Some of the seedlings were teetering on nearly severed stems, but others were toppled or missing outright. People dealing with this problem are often told they are incorrect in their diagnosis. Before anyone suggests alternative culprits like cutworms or slugs, let me emphasize that I am pretty good at identifying pests and have obtained proof on countless occasions that pillbugs are in fact, whodunnit.
If you need further assurance that they aren’t always friendly denizens of the compost heap, here are other sources describing their destructive abilities:
- University of Idaho — pillbug and sowbug damage
- University of Nebraska — pillbugs damaging soybean seedlings
- Kansas State University — pillbugs as pests
- Texas A&M — pillbugs as pests
- University of Missouri — pillbugs as pests
- University of California — pillbugs as pests
- GardenWeb forums — pillbugs burrowing in strawberries
- GardenWeb forums — more problems with pillbugs
The problem is, a lot of the advice that people give simply isn’t accurate or effective. Popular word-of-mouth solutions aren’t necessarily based on personal experience. Additionally, gardeners are usually poor scientists. They try something and if it works, they think it fixed their problem. The reality is that it could have been brought about by other means the gardener didn’t notice.
We really need some brainstorming to solve this issue for organic and permaculture growers!
Here’s what I know for sure about pillbugs:
- They’re neat! As crustaceans, they’re more closely related to shrimp than insects. They breathe through gills and need moisture to survive. Also, their scientific family is Armadillidiidae, which is pretty adorable.
- Their favorite conditions are identical to the favorite conditions of most plants. They’re also able to burrow to find moisture and do not leave a garden entirely during brief droughts. Once irrigation occurs, they’re back. In order to completely remove them from an environment, you’d need to create a desert situation.
- Diatomaceous earth isn’t effective in moist conditions. Also, I have witnessed pillbugs nesting in it.
- Free-range chickens are only temporarily excited to eat pillbugs when they are abundant. My brown leghorns will still eat them half-heartedly, but my other two breeds turn up their beaks. In two years of owning chickens I have noticed no reduction in the pillbug population, even when the poultry fence was broken and they had months of unrestricted access to the entire yard.
- They seem to be active year-round in my climate.
- They do like mulch, but so do plants and the rest of the soil food web. Also, even when I let a seedling bed bake in the sun the pillbugs come out from nearby hiding areas at night.
- They don’t like bright light.
- They drown easily and it appears to occur evenly whether you use water or beer.
- They will collect in rolled up moist cardboard or upturned grapefruit rinds the same way that slugs do. They often nest just under the soil next to plants they like to consume.
- They seem to cause regional problems. I know of multiple farms and gardens in the upstate of South Carolina with this predicament, but have yet to find a grower in North Carolina experiencing the same issues. People who do not have this problem look at you like you’re nuts when you bring it up.
- There must be an environmental factor that keeps their numbers under control if there are regions of the country where they aren’t a problem. We just have to figure it out.
One thing I would like to try, but do not currently have the means to do so, are ducks. Does anyone have experience using them for this purpose?
Regarding the infestation in my seed trays: I pulled them out of the bottom of the cold frame and balanced them on the straw bales. My reasoning is that the bright light exposure from all sides will drive the pillbugs off of the seedlings. I’m also considering water traps tucked inside the frame to cause drowning.
Consider this an open discussion. What would you do? Is there anything you’ve tried and did it work? No idea is too stupid, we could really use your help!
*Update: my husband’s first suggestion is that we eat them. Any suggestions on how to harvest them easily?* 😉