In the Sandbox we try to incorporate many Native plants into the landscape. My husband's favourite is the Lilium superbum or Turk's Cap Lily. This is a lovely plant with orange petals dotted with black speckles and long stamens. It grows in our front flowerbed on the north side of the house. The soil there is slow to warm up and through the summer can be quite dry.
At this time of the year on the lily this type of damage occurs. The leaves are torn and full of holes. Not appealing foliage.
This is the problem. The Lily Leaf Beetle or Lilioceris lilii is the culprit. This beetle was introduced to North America from Eurasia. As an adult this brilliant red beetle lays its eggs on the undersides of leaves. The larvae are orange-red and carry a layer of excrement on their backs. One generation is produced a year. The adults and larvae eat leaves, flowers and seed cases. The entire plant parts can be consumed. Not only lilies are affected but Fritillarias and enven potatoes can be attacked.
In Ontario we are not allowed to use fungicides, pesticides or herbicides to control insects and weeds under the Ontario Cosmetic Pesticides Ban which came into effect On April 22, 2009. In our garden we abstain from using any kinds of pesticides anyway so that we can keep a proper balance for biodiversity. The method above which I am sorry is out of focus, is my two finger method. You get the beetle between your thumb and finger and give him a squish. Believe me it is a very satisfying and thorough method of elimination. Give it a try on your lily beetles. Happy Gardening.