With lush foliage and big, beautiful flowers, canna lilies come in various types, all of which originate in tropical climates. Best suited to mild, sunny places, canna lilies will die if left outdoors in freezing winter temperatures, but can be grown as annuals in warm locales. Though they're easy to grow, canna lilies are also susceptible to various pests and diseases that gardeners should be aware of.
A type of caterpillar, the leaf roller is roughly three quarters of an inch long with an orange head. As they grow, leaf rollers turn yellow and finally, dark green before they finally turn into brown moths. Leaf rollers devour canna lily leaves and bind them together with silky strands, creating a place to hide and feed. The leaves of an infested plant are covered in black leaf-roller droppings.
Snails and Slugs
Hungry snails and slugs love to feed on canna lilies and will cover the plant's leaves with holes. To keep these pests away, remove any debris gathered around the base of the canna lilies, leaving them with nowhere to hide. Inspect the lilies at night when snails and slugs come out to feed, removing them from the plant and dropping them into a bucket of soapy or salted water. If the problem persists, use traps or a commercial bait to kill them.
Tiny, green and mean, aphids breed quickly and will take over a canna lily plant, and even an entire garden, if left unchecked. Feeding on the sap of succulent canna lilies, a swarm of hungry aphids also carry diseases from one plant to the next. In the case of just a few aphids, pluck them off one at a time and squish them. Alternately, spray the lily down with a hose to blast away aphids. If the infestation persists, consider using a commercial insecticide.
Botrytis blight is a disease caused by fungus, which thrives in humid weather. Infected canna lilies will be covered in a fuzzy, gray mold and may also have damaged sections of watery, soft tissue. The condition can affect just a few leaves or flowers or the entire plant. Inspect canna lilies regularly for signs of botrytis blight and trim away any damaged parts of the plant. Treat canna lilies with a commercial fungicide to control the problem and prevent its spread.
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