Leaf Nibblers: Friend or Foe?

Caterpillar eating a leaf.

It can be concerning when you find signs of insects chewing on your plants, but keep in mind that beneficial insects, including some of our favourite pollinators, depend on your plants’ leaves for various stages of their lifecycles. In most cases, plants can tolerate occasional nibbling and gardeners don’t need to take any action.

Leaf-nibbling Insects we Welcome to our Gardens

  • Monarch caterpillars: After their long flight north, monarchs search for milkweed to lay their eggs on. Once the eggs hatch, the young caterpillar will eat the leaves of the milkweed.
  • Black swallowtail caterpillars: Before they emerge as beautiful, black and yellow butterflies, these caterpillars rely on plants in our vegetable and flower gardens for food. This includes dill, parsley and carrot tops and the native wildflower, golden Alexander.

Some Visitors to be Monitored and Managed

  • Aphids: These tiny, soft-bodied insects suck juices from various plant parts causing wilting, discolouration or curling of leaves and flowers. Remove the aphids with a blast of water from the garden hose being careful not to damage delicate buds or flowers. Cut and dispose of heavily infested plant parts. If necessary, spray the aphids directly with an insecticidal soap. Make your own by mixing a few tablespoons of a pure liquid soap (such as castile) in a small bucket of water. Ladybugs, especially those in their larval stage, are natural predators of aphids.
  • Slugs and snails: After a night of chewing, these soft-bodied creatures leave behind large holes in leaves. The best way to control them is to hand-pick them off your plants at night and drop them into a bucket of soapy water. Invite birds, toads and even snakes into your garden to naturally manage slugs and snails. 
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