Published on 07/16/09

Beetles and caterpillars love cannas

By Sharon Dowdy
University of Georgia

The canna lily is a Southern favorite. The perennial bulb can grow six feet tall and is often used to create colorful borders. The problem is insects love them, too.

University of Georgia entomologist Kris Braman is searching for canna lily varieties that are the most resistant to Japanese beetles and canna leaf rollers. These two pests destroy the plants by feeding on their leaves. The beetles eat the flowers, too.

Incased caterpillars

Canna leaf roller caterpillars seal themselves in the plant’s leaves by literally sewing themselves inside using their silk.

“They make silk stitches along the sides of the leaves and curl the leaves up like cigars,” said Braman, a researcher with the UGA College of Agricultural and Environmental Sciences. “They feed on and skeletonize the leaves which give them a beaten and tattered appearance.”

Braman says there aren’t any totally “immune or bulletproof” canna lily varieties, but there are some less susceptible. Her research is in the early stages, but after studying some 22 varieties, she has found the Maudie Malcom variety to be the most pest resistant.

This variety can tolerate insect damage in the early stages and still remain attractive, she said.

They love to smell the flowers

Japanese beetles are attracted to canna lilies because of their floral scents. Beetles form clusters on the lilies’ leaves.

“First they smell the flowers. Then they notice the foliage,” Braman said. “The beetles then emit a pheromone that attracts other beetles.”

To help prevent leaf rollers from making a home in their canna lilies, homeowners should clean up and remove any debris from last year’s lilies, she said. The debris can harbor pests.

Bacillus thuringiensis, or Bt, insecticide can be used to control small caterpillars. A contact or systemic insecticide may be required to control larger caterpillars and Japanese beetles, Braman said.

Tall and colorful

Growing from three feet to over six feet in a single season, canna lilies originated in South America and the West Indies. Canna lilies are available in a variety of colors, the most popular being yellow, orange, red or a combination of the three.

The plants die back in the winter and leaf out and bloom in warmer months. If grown in cold winter areas, the rhizomes should be dug up and stored in a cool area for the winter, then planted after the threat of frost has passed.

Canna lilies grow best in full sun in well-drained or sandy soil.

They are used in mixed borders, massed in garden beds by themselves and tucked between small to medium shrubs. Dwarf varieties work well as edgings and in large containers with smaller plants.

Sharon Dowdy is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.