Crown Rot

Crown rot is the most devastating disease for waterlilies. It will spread by infected plants getting introduced to the pond. As far as we know there is no control, but destruction of infected plants. Yellowing leaves in the midsummer and no new growth are indicators, and then the crown will eventually rot away.

Fasarium

Fasarium is a common soil or water borne fungus, that will only affect a few aquatics.

Rust

Rust is another disease of cannas, but this one is curable. Canna rust will appear as orange dust on the leaves. Cut off and remove an foliage that is damaged. In the fall when the cannas should be dormant, cut the foliage to the ground and remove it from the pond. Spray the remaining crown with a solution of ten percent bleach. Also remove the top inch of soil. This measure should prevent new infection when the new shoots emerge in the spring.

Sooty Mold

Sooty Mold is accompanied by an insect infestation and is the result of the insects giving off a sugary secretion called honeydew. The fungus feeds on both the honeydew and the plant. Spray with a 5-10 solution of hydrogen peroxide.

Virus

Viruses are everywhere and can affect virtually any plant. The one most often encountered in the pond is a canna virus. The plants look burned and never recover. Each new shoot is affected. The only control is to destroy the plant and start over. Canna virus is spread by sucking insects, and in my case Japanese beetles were the vectors.