Have the rhizomes rotted?
Are the leaves rolled?
Are the leaves discolored, fine webbing may be present?
Do the leaves have large, ragged holes in them?
Are the leaves covered in coarse stippling and may appear silvery?
Rhizome Rot (caused by Sclerotium rolfsii, Fusarium spp.) causes rhizomes to decay and stems to rot at the base of the plant. Infection may be accompanied by a cottony fungal growth. Discard damaged roots. Plantings should be regularly thinned and re-planted to improve vigor. The fungi are best controlled through the selection of healthy rootstock.
Rolled leaves are caused by canna leafrollers caterpillars. These green caterpillars with brown heads feed on the enclosed leaves and buds. If the infestation isn't severe, handpick the rolled leaves with caterpillars. For severe infestations, the use of insecticides is the only way of controlling.
Spider mites are known to cause problems for Tropicanna Gold Canna. Hose off plants when symptoms first appear. A strong stream knocks mites off plants and may give control. Introduce predatory mites. For severe infestations, spray plants with insecticidal soap or pyrethrin.
Large, ragged holes in the leaves are caused by slugs and snails. Slugs and snails feed on the plant leaves usually at night. To control slugs and snails use diatomaceous earth around your plants. You can also handpick them during the night or use shallow dishes filled with beer as a trap.
These symptoms may indicate thrips. Thrips are tiny, yellow to black flying insects. Severely infected plant parts should be removed and destroyed. Control thrips by introducing lady beetles or lacewings, their natural predators. Insecticidal soap helps in severe infestations.
Some environmental issues may have caused an unhealthy look in your Tropicanna Gold Canna. Cannas love warm soil, 60°F or warmer. They need a position in full sun and fertile, moist soil. If you live in a zone with harsh winters, dig up canna rhizomes in the fall and replant them again in the spring.
Wilen, C., Dimson, M., Plant and Pest Guide - Los Angeles State Historic Park, The University of California, Division of Agriculture and Natural Resources
Ellis, B. W., Bradley, F. M., & Atthowe, H. (1996). The Organic gardener's handbook of natural insect and disease control: a complete problem-solving guide to keeping your garden & yard healthy without chemicals. Emmaus, Pa.: Rodale Press.
Sreten null
Hi! I’m Sreten Filipović. I graduated from the Faculty of Agriculture at the University of Belgrade, with a master's degree in Environmental Protection in Agricultural Systems. I’ve worked as a researcher at Finland's Natural Resources Institute (LUKE) on a project aimed at adapting south-western Finland to drought episodes. I founded a consulting agency in the field of environment and agriculture to help farmers who want to implement the principles of sustainability on their farms. I’m also a founding member of the nonprofit organization Ecogenesis from Belgrade whose main goal is non-formal education on the environment and ecology. In my spare time, I like to write blog posts about sustainability, the environment, animal farming, horticulture, and plant protection. I’ve also published several science-fiction short stories.
You can find me on LinkedIn at https://www.linkedin.com/in/sreten-filipovi%C4%87-515aa5158/
