Canna, those semi-tropical rhizomes with magnificent eye-popping flowers, are a cinch to grow in warmer regions. Even northern gardeners can enjoy them as annuals. Canna lilies have few problems and can overwinter with some protection in the ground in USDA zones above 8. Canna lily pests are rare, but their broad sword-like leaves are awfully attractive to a variety of leaf munchers. Read on for some ideas on insects that attack Canna lily plants and how to recognize and defeat them.
Canna Lily Pests
The large funnel-shaped spikes and brilliant Flamenco dancer colors announce the blooming period of a Canna. They are marvelous plants with a tropical flair and an amazing ability to reproduce themselves as rhizomes replicate. Generally, a sunny location with well-draining soil and average water is enough to ensure summer blooms and healthy glossy broad leaves. Occasional pest problems do occur as in any plant. Pests of Canna lilies usually come under the categories of sucking and chewing insects.
Many of the insects that attack Canna lily plants are obvious and easy to recognize. Some insects that attack Canna lily plants are tiny and hard to see, however. Thrips are one of these. They are practically microscopic and need special methods to view them and determine their existence. Place a piece of paper under the leaves and flower spikes of your plant and gently shake it. If tiny black objects are seen on the paper, you likely have thrips on the Canna.
Another common sucking insect is the spider mite. These are also tiny but are more easily recognized by finding their webs. Citrus mealybug is a cottony looking insect and scale is one of the sucking pests of Canna lilies that appears to be small bumps on stems and foliage petioles.
Among the more common pests on Canna are caterpillars and larvae. Canna leafrollers are larvae of Brazilian skippers and chew straight rows of holes in leaves. Many other infant insects may find Canna leaves delicious. Among possible suspects are:
- Corn earworm
- Wooly bear caterpillars
- Saddleback caterpillars
These are usually obvious and chemical Canna lily pest control is not necessary. Foliar damage from chewing doesn’t usually affect the plant’s health but it does mar the overall appearance. Unless there is a sudden infestation of many caterpillars or larvae, hand picking is usually sufficient to control and slight problems.
Canna Lily Pest Control
Many of the sucking insects can simply be rinsed off. Others may require a few weeks of spraying with horticultural oil or soap.
In the greenhouse, wipe off leaves with a dilution of rubbing alcohol to control scale and mealybugs.
Handpicking and crushing the larger caterpillars, slugs and snails is effective but rather distasteful.
Bait and traps are often your best allies, as well as removing any old plant material that can overwinter and harbor pests.
One of the hardest insects to control is the Canna leafroller. This larvae survives winter in rolled leaves on the plant. Remove and destroy leaves in winter. If the plant is heavily infested, spray with Bacillus thuringiensis, a natural bacteria that is very effective against a host of larvae.