The Canna is a genus that is comprised of flower plants. There are 19 species within the genus. Cannas are commonly referred to as canna lilies, although they are not truly lilies. They are part of the Cannaceae family. Cannas are notable for their attractive and showy foliage, and also for being one of the planet's primary sources for starch. As with any plant, there are several possible problems that cannas could experience.
Compared with other genera, cannas are lucky enough to be relatively disease-free. However, cannas that are grown within the United States can be victimized by a fungus that is known as canna rust. This disease is characterized by the development of orange spots on the leaves of the plant. This results from soil that is overly moist. Cannas are also prone to various plant viruses, several of which are specific to them alone. These viruses cause symptoms such as streaking or spotting of the leaves, but can ultimately result in distorted and twisted foliage and blooms, as well as stunted growth. Another possible canna disease is botrytis, which displays itself as a fuzzy and gray mold. In times of humidity, it often appears on older flowers.
In general, cannas are pest-free. However, those that are grown within the United States are occasionally victimized by the canna leaf roller, which is two separate insects (the Brazilian skipper butterfly's larvae, and also the larvae of a moth known as the lesser canna leaf roller). These pests damage the leaves of the canna by sewing them shut before they are able to unfurl. Snails and slugs are also attracted to cannas, and often leave big holes on the leaves (especially the young, unfurled leaves). In the summertime, cannas might also be prone to damage from red spider mites that are grown indoors. Japanese beetles can also be problematic to the plants.
Botrytis can be treated by simply eliminating the older flowers on which the mold appears. This is to make sure the mold does not spread to other flowers. Canna rust can be handled by getting rid of and throwing out the foliage that is affected. A copper-based liquid spray can also be used as a prevention method, as well. It should be sprayed on the sides and stems of the leaves. With pests, if the infestation is light, simply cutting off and throwing out the affected leaves off should suffice. However, in more serious cases, chemical insecticide sprays should be applied to the plants in order to prevent spread.