Do Roly Polys Hurt Plants? - Plant Care Guide

Generally, roly polys (also known as pill bugs or sow bugs) do not hurt healthy plants; they are primarily detritivores, meaning they feed on decaying organic matter in the soil. In fact, they can be beneficial in the garden by breaking down dead plant material and enriching the soil. However, in large numbers or under specific conditions, they can occasionally nibble on tender seedlings or soft fruits, causing minor damage.

What Exactly Are Roly Polys?

Roly polys, scientifically known as pill bugs (Armadillidium vulgare) and sow bugs (Porcellionides pruinosus and others), are fascinating creatures that often spark curiosity in gardens. Despite their insect-like appearance, they are actually crustaceans, more closely related to shrimp and crabs than to insects. They are the only crustaceans that have fully adapted to living on land.

Here's a closer look at what roly polys are:

• Classification: They belong to the order Isopoda within the subphylum Crustacea.
• Appearance:
  • Typically oval-shaped with a segmented, grayish-brown, or dark gray body.
  • They have seven pairs of legs (14 legs in total).
  • They possess two pairs of antennae, though one pair is usually very short and hard to see.
  • Pill bugs have the distinctive ability to roll into a tight, protective ball when disturbed (hence "roly poly").
  • Sow bugs look very similar but are usually flatter and have two small tail-like appendages (urojods) at their rear; they cannot roll into a ball.
• Habitat: They thrive in damp, dark environments where decaying organic matter is abundant. You'll find them under rocks, logs, leaf litter, mulch, pots, and in compost piles.
• Diet (Detritivores): Their primary diet consists of dead and decaying plant material, such as fallen leaves, rotting wood, and other organic debris. This makes them valuable decomposers.
• Reproduction: Females carry their eggs in a specialized pouch (marsupium) on their underside until they hatch into miniature versions of the adults.
• "Land Crustaceans": Unlike most crustaceans that live in water, roly polys have adapted to terrestrial life but still require high humidity to breathe through gill-like structures. This is why they are always found in moist environments.

Despite their often-misunderstood nature, roly polys play an important ecological role as nature's little cleanup crew.

What is the Primary Diet of Roly Polys?

The primary diet of roly polys (pill bugs and sow bugs) consists almost entirely of dead and decaying organic matter. They are highly beneficial detritivores and decomposers in garden ecosystems.

Here's a breakdown of their main food sources:

• Dead Plant Material: This is their staple. They feed on:
  • Fallen leaves
  • Rotting wood
  • Decomposing mulch
  • Compost
  • Dead grasses and weeds
  • Any other decaying plant debris on the soil surface or slightly beneath it.
• Fungi: They will also consume various types of fungi that grow on decaying matter, further aiding in the decomposition process.
• Other Microbes: They contribute to the breakdown of other microorganisms associated with decomposition.
• Animal Waste: While less preferred, they may also consume animal droppings found in their habitat, contributing to nutrient cycling.

By consuming this dead organic material, roly polys play a vital role in the nutrient cycle. They break down complex organic compounds into simpler forms, making nutrients available for plants and improving soil structure. This process enriches the soil, much like earthworms do.

The misconception that they harm healthy plants often arises when they are observed in large numbers, but in most cases, they are merely performing their ecological role by cleaning up the garden floor.

When Do Roly Polys Become a Problem for Plants?

Roly polys typically only become a problem for plants when their numbers are extremely high or when their preferred food source (decaying organic matter) is scarce. In these specific situations, they may turn to live plant material out of necessity.

Here's when roly polys can cause damage:

• Tender Young Seedlings: This is the most common scenario for damage.
  • Why: Newly sprouted seedlings or delicate transplants have very soft, tender stems and leaves that are easy for roly polys to chew. If there's not enough decaying organic matter readily available, they might start nibbling on these vulnerable plants, often girdling (chewing around the base of) young stems or munching on the first delicate leaves.
  • Impact: This can stunt or even kill young plants.
• Soft, Ripening Fruits or Vegetables:
  • Why: Roly polys will sometimes feed on ripe or overripe fruits and vegetables that are lying directly on the soil surface. Examples include strawberries, melons, pumpkins, and tomatoes that are in contact with the ground. The soft skin of these fruits is easily pierced.
  • Impact: Creates unsightly holes or blemishes, making the produce unmarketable or leading to rot.
• Lack of Decomposing Matter:
  • Why: If your garden beds are too "clean" with very little mulch or decaying leaves, a large population of roly polys might be forced to seek alternative food sources, making live plants more appealing.
• High Population Density:
  • Why: Even if their primary food is available, an overwhelming number of roly polys might simply consume so much that some damage to live plants becomes inevitable as they forage widely.
• Stressed or Damaged Plants:
  • Roly polys are more likely to feed on plants that are already stressed, weak, or have existing damage, as these are easier to consume.

In most well-maintained gardens with sufficient organic mulch and compost, roly polys remain beneficial decomposers. It's when an imbalance occurs that they might shift from friend to foe.

What Do Roly Poly Damage on Plants Look Like?

Roly poly damage on plants has some distinctive characteristics, especially when they stray from their usual diet of decaying matter and begin feeding on live plant tissue. Recognizing this damage helps in differentiating it from other pests.

Here's what roly poly damage typically looks like:

• On Young Seedlings:
  • Girdling: This is common. They chew around the base of the stem of very young seedlings, sometimes severing it completely, causing the seedling to collapse and die.
  • Irregular Holes: They may chew small, irregular holes in delicate, new leaves.
• On Soft Fruits/Vegetables (on the ground):
  • Shallow, Irregular Holes: They create shallow, often numerous, irregular holes or scrapes on the surface of soft-skinned fruits like strawberries, melons, or tomatoes where they touch the soil.
  • Starting Spots for Rot: These feeding wounds can then become entry points for fungi and bacteria, leading to further decay and rot of the fruit.
• On Leaves (less common on mature plants):
  • While rare on tough, mature leaves, they might chew small, irregular holes or scrapes on the undersides of soft leaves, especially if the leaf is touching damp soil.
• Key Distinguishing Factors:
  • Location of Damage: Damage is almost always at ground level or on parts of the plant touching the ground.
  • Chewing vs. Sucking: Roly polys have chewing mouthparts, so the damage will be holes or chewed edges, not sap-sucking damage (like stippling from spider mites or curling from aphids).
  • Absence of Slime Trails: Unlike slugs and snails, roly polys do not leave behind silvery slime trails.
  • Presence of the Pest: You'll often find the roly polys themselves near the damage, especially at night or when you lift mulch/pots.

If you see these types of damage, particularly on young plants or ground-level fruits, and observe roly polys in high numbers, it's a strong indicator they might be responsible.

How Can You Prevent Roly Poly Damage to Plants?

Preventing roly poly damage to plants typically involves reducing their population in vulnerable areas and ensuring they have ample alternative food sources, rather than outright eradication. The goal is to discourage them from feeding on live plants.

Here are effective strategies:

1. Reduce Moisture and Shelter in Vulnerable Areas:
   • Remove Hiding Spots: Roly polys love damp, dark places. Regularly clear away excessive leaf litter, weeds, flat boards, bricks, or debris from around the base of vulnerable seedlings and fruits.
   • Improve Air Circulation: Space plants adequately and prune lower leaves to improve airflow and allow the soil surface to dry more quickly.
   • Water Smart: Water in the morning so the soil surface has time to dry during the day. Avoid overwatering.
2. Provide Alternative Food Sources (Away from Vulnerable Plants):
   • Strategic Mulch: Use organic mulch (like wood chips or straw) in garden paths or around mature plants, but keep it pulled back a few inches from the base of seedlings or developing fruits. This provides them with plenty of decaying matter to eat, distracting them from your plants.
   • Compost Piles: A well-maintained compost pile offers an excellent food source, drawing them away from garden beds.
3. Physical Barriers:
   • For Seedlings: Create collars around the base of very young, tender seedlings using plastic cups (bottom cut out) or cardboard tubes. This creates a physical barrier they often can't climb.
   • For Ground Fruits: Elevate fruits like strawberries off the soil using straw mulch or special strawberry supports. For melons and pumpkins, use a piece of wood, tile, or a small trellis to keep them off the damp ground.
4. Trapping (Manual Removal):
   • Place shallow dishes filled with beer, cornmeal, or rotting fruit near affected areas. Roly polys are attracted to these. Check traps daily and dispose of collected pests.
   • Lay out moist newspaper, cardboard, or overturned melon rinds. Check under them in the morning to collect and relocate (or dispose of) the pests.
5. Encourage Predators:
   • Birds, toads, and some predatory ground beetles will feed on roly polys. Creating a diverse, healthy garden ecosystem can help maintain a natural balance.

By focusing on habitat management and providing alternative sustenance, you can minimize roly poly damage without harming these generally beneficial garden inhabitants.

Are Roly Polys Beneficial to the Garden Ecosystem?

Yes, roly polys are indeed beneficial to the garden ecosystem, primarily serving as important decomposers and contributing positively to soil health. Their role as nature's cleanup crew often outweighs any occasional damage they might cause.

Here's how roly polys benefit the garden:

• Decomposition of Organic Matter: This is their most significant contribution. They break down:
  • Fallen leaves
  • Dead plant debris
  • Rotting wood
  • Animal waste By consuming these materials, they help to recycle nutrients and prevent the buildup of undecomposed matter.
• Nutrient Cycling: As they consume organic debris, they excrete waste products that are rich in readily available nutrients. This process helps to return essential nutrients (like nitrogen, phosphorus, and potassium) back into the soil in a form that plants can easily absorb.
• Soil Improvement: Their feeding and burrowing activities contribute to improving soil structure and aeration. They can help break up compacted soil, allowing for better water infiltration and oxygen penetration to plant roots.
• Fungal Control (Minor): By consuming decaying matter, they can also help control the growth of certain fungi that might otherwise proliferate on rotting debris.
• Food Source for Predators: Roly polys themselves become a food source for other beneficial creatures in the garden, such as predatory beetles, birds, and toads, contributing to the garden's overall biodiversity and food web.
• Pest Identification: Their presence can sometimes serve as an indicator. A sudden population boom might signal that there's an abundance of decaying matter (or possibly too much moisture) that needs addressing, or that their usual predators are missing.

In a balanced garden, roly polys are industrious workers that quietly contribute to a healthier, more fertile soil environment, demonstrating their valuable place in the natural world.

What is the Difference Between Pill Bugs and Sow Bugs?

While often grouped together as "roly polys," pill bugs and sow bugs are distinct creatures, though both are terrestrial isopods that thrive in similar moist, decaying environments. The main difference lies in their physical characteristics and defensive behaviors.

Here's a table comparing them:

Both pill bugs and sow bugs are beneficial detritivores that help break down organic matter in the garden. For most gardeners, distinguishing between the two isn't critical for management, as their diet and the strategies to prevent plant damage are largely the same. However, knowing the difference can be a fun bit of natural history!

What Other Decomposers are Beneficial in the Garden?

Roly polys are just one part of a vast army of beneficial decomposers that work tirelessly to maintain a healthy and fertile garden ecosystem. These organisms break down dead organic matter, cycling nutrients back into the soil and improving its structure.

Here are some other crucial decomposers beneficial in the garden:

• Earthworms:
  • Role: The undisputed champions of soil health. They tunnel through the soil, creating channels for air and water. They ingest soil and organic matter, breaking it down, and excrete nutrient-rich castings that improve soil fertility and structure.
  • Benefits: Aeration, drainage, nutrient cycling, improved soil structure, humus formation.
• Fungi (Decomposer Fungi):
  • Role: Numerous species of fungi (e.g., saprophytic fungi, mycorrhizal fungi) are critical decomposers, breaking down tough organic materials like wood, cellulose, and lignin that bacteria often can't.
  • Benefits: Essential for breaking down woody debris, releasing nutrients, and forming soil aggregates. Mycorrhizal fungi also form symbiotic relationships with plant roots, enhancing nutrient uptake.
• Bacteria (Decomposer Bacteria):
  • Role: Billions of bacteria in the soil are involved in every stage of decomposition, breaking down organic matter into simpler compounds. They are especially crucial in the nitrogen cycle.
  • Benefits: Mineralization of nutrients, nitrogen fixation, pathogen suppression.
• Nematodes (Beneficial Species):
  • Role: While some nematodes are plant pests, many are beneficial. Decomposer nematodes feed on bacteria and fungi, releasing nutrients into the soil as they graze.
  • Benefits: Nutrient cycling, soil food web health.
• Millipedes:
  • Role: Like roly polys, millipedes are detritivores, primarily feeding on decaying plant matter in moist environments. They have two pairs of legs per body segment (compared to one pair for centipedes and roly polys).
  • Benefits: Decomposition, nutrient cycling.
• Slugs and Snails (with caveats):
  • Role: While notorious plant pests, slugs and snails do consume decaying organic matter and fungi, contributing to decomposition.
  • Caveats: Their damage to live plants often outweighs their benefits as decomposers, so their populations typically need to be managed.
• Other Insects and Arthropods:
  • Springtails, mites, collembolans: Tiny creatures that feed on fungi, bacteria, and decaying organic matter, playing a role in the microbial food web.

A healthy garden relies on a vibrant and diverse community of these decomposers working together to transform dead matter into life-giving soil, making the gardener's job much easier and more sustainable.

Should I Be Concerned About Roly Polys Indoors?

Generally, you should not be overly concerned about roly polys indoors, as they are not typically considered a household pest in the same way ants or cockroaches are. Their presence indoors usually indicates a specific moisture problem that needs addressing.

Here's why and what to do if you find them indoors:

• No Threat to Indoor Plants: Roly polys primarily feed on decaying organic matter. Indoors, they typically won't bother your healthy houseplants, as these plants don't provide their preferred diet of rotting debris. They might, however, feed on decaying leaves in a houseplant pot if the soil stays too wet.
• Harmless to Humans and Pets: Roly polys are completely harmless to humans and pets. They don't bite, sting, or carry diseases.
• Indicator of Moisture: Finding roly polys indoors is almost always a sign of a moisture problem. They cannot survive in dry indoor environments and seek out damp conditions. Common places to find them include:
  • Damp basements or crawl spaces.
  • Under leaky sinks or pipes.
  • Near condensation issues (e.g., around windows, dehumidifiers).
  • In bathrooms with poor ventilation.
  • Around rotting wood or damp cardboard boxes.
• What to Do if You Find Them Indoors:
  1. Identify the Source of Moisture: This is the most important step. Find and fix any leaks, improve ventilation, or dehumidify the area.
  2. Clean Up Organic Debris: Remove any damp cardboard, rotting wood, or wet leaf litter that might be providing them with food and shelter.
  3. Seal Entry Points: If they are coming in from outside, seal cracks in foundations, around windows, and under doors.
  4. Physical Removal: You can simply sweep them up and release them outside in a damp, mulched area, or dispose of them.
  5. Avoid Pesticides: There is no need to use harsh chemical pesticides for roly polys indoors. Addressing the moisture issue will naturally deter them.

So, while their presence indoors might be startling, view roly polys as a helpful indicator that you have a moisture issue that needs attention, rather than a pest problem in themselves.