Canna Gets Black Stuff In Leaf Folds And Turns Brown And Does Not Open Or Flower

A: Marie, I think your Cannas may have lessor leaf roller caterpillars. Here is what Tony Avent recommends for control. Without question, the worst pest of Canna is a caterpillar known as the lesser canna leaf-roller, which is primarily found in the southern US. The canna leaf-roller moth lays eggs in the bud of the developing stalk. These hatching caterpillars use a sticky webbing to keep the leaf from unfurling, which protects them from predators and insecticide sprays. They feed and pupate inside the rolled-up leaf and can cause significant damage to the developing stalks. Some Canna are more susceptible to damage by canna leaf-rollers than others. Typically, the closer to the species the Canna are, the less damage that we see. Canna glauca, for example, is virtually untouched. The key to controlling canna leaf-rollers is vigilance. Leaf-rollers can be a problem as early as spring, so keep a close eye for the first sign of webs holding the newly emerging leaves together. Opening the leaves and removing the offending caterpillars will work on a small scale, but in larger plantings, you can simply clip off the top half of the rolled leaf. Insecticides such as Dipel and Safer Caterpillar Killer (Bacillus thuringensis) can be sprayed into the bottom half of the leaf so that it reaches the caterpillars. If the leaf-roller population is high, you may need to spray throughout the growing season, but as you reduce the moth population, the need to spray lessens. Again, the key is to monitor your plants and not allow the larvae to mature, which starts the cycle over again. - See more at: http://www.plantdelights.com/Article/Canna-Lily#sthash.1hn7cKzr.dpuf Best And Happy Yardening, Nancy