Cannas Pests and Diseases

Pests

Cannas are largely free of pests but in the USA plants sometimes fall victim to the Canna Leaf Roller and the resultant leaf damage can be most distressing to a keen gardener.

Slugs and snails are fond of Cannas and can leave large holes in the leaves, preferring the tender young leaves that have not yet unfurled. Red Spider Mite can also be a problem for Cannas grown indoors or during a very hot, long summer outdoors. The Japanese Beetles will also ravage the leaves if left uncontrolled.

Disease

Canna are remarkably free of disease, compared to many genus. However, they may fall victim to canna rust, a fungus resulting in orange spots on the plant's leaves, caused by over moist soil. Cannas are also susceptible to certain plant viruses, some of which are Canna specific viruses, which may result in spotted or streaked leaves, in a mild form, but can finally result in stunted growth and twisted and distorted blooms and foliage.

The flowers are sometimes affected by a grey, fuzzy mould called Botrytis. Under humid conditions it is often found growing on the older flowers. Treatment is to simply remove the old flowers, so the mould does not spread to the new flowers.