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Sowbugs, or pillbugs as they are sometimes called, are a common complaint of gardeners. They are not true insects, but crustaceans. Grey in colour and segmented, with multiple legs, they curl up into a ball when disturbed. They like areas that are moist, usually with a lot of decaying materials, such as compost, where they are actually valuable in breaking down organic material. In higher numbers, however, they can seedlings or any plant or fruit that has been already damaged. So control measures should involve areas where your plants are growing:

  • Avoid watering late at night, or drain wet areas.
  • Remove unnecessary shade, e.g., by dividing perennials often.
  • Remove any large quantities of decomposing materials, e.g. rotting wood stumps.
  • If you notice sowbugs or pillbugs entering your home, ensure all cracks and crevices are properly sealed.
  • Set up boards or stones to serve as traps that can be emptied regularly.
  • Sprinkle diatomaceous earth (containing silicon dioxide) around plants or areas where you want to keep sowbugs out. The barrier should be at least 15 cm (6 in.) wide. This product works as an abrasive on the outer coating of the sowbug, resulting in dehydration; it works best under dry conditions and may require frequent reapplication.
  • When mulching plants, consider using clear plastic on top to heat up the soil. The increased temperature will discourage sowbugs from hibernating under the mulch.
  • Sterilize your compost before using it in the garden. To do this, spread a thin layer of the compost over the soil and cover with clear plastic, again to heat it up.
  • Keep plants healthy, especially young seedlings. Avoid placing seedlings out too early; sowbugs rarely attack healthy plants.
  • Make paper traps by folding up a sheet of paper like a tent and painting the inside with a sticky substance.