Recognizing Japanese Beetles

• Signs of damage to the leaves of canna lilies will probably be the first thing that alerts you to a beetle problem. The beetles will chew holes in the leaves. Turn the damaged leaves over and inspect for beetles. Japanese beetles are copper and metallic green in color and have six legs. The beetles tend to be attracted to each other, so if you see one or two beetles, there are likely many more scattered throughout the plants.
  
  

Removing the Beetles

• The easiest and most effective way to strip Japanese beetles from canna lilies is to pick them off by hand. The beetles will be easiest to pick off in the morning. Get up early and inspect the back side of each leaf, collecting the beetles as you find them. Alternately, you could place a tarp under the plants and try shaking them off and collecting them off of the tarp.
  
  

Killing the Collected Beetles

• You will need to kill the collected beetles so they don't simply return to the canna lilies. Drown them in a bucket of soapy water or collect them in a container and freeze them in the freezer. You could also put them in a container and squish them, though this method is less likely to kill every single beetle. No matter which way you choose to kill them, dispose of the dead beetles far away from the canna lilies as the scent omitted from the beetles' bodies will attract more beetles.
  
  

Maintaining Lilies

• After you remove and kill the beetles, spray the leaves of the canna lilies with a insecticide spray. Be careful that none of the spray gets on the flowers of the plants, as it can interrupt insects that participate in the pollination process. Even after spraying, be sure to return to the lilies each morning to inspect for beetles.