Tropical plants can be planted outdoors year round in warmer climates or during the summer in cooler climates. Tropical plants are also used as houseplants. Common tropical plants include palm, ginger, tropical hibiscus, elephant ears, African lily and canna. Tropical plant diseases include root rot and leaf spot, both fungal and bacterial.
Root rot is a common tropical plant disease. Symptoms include yellowing leaves and a failure to grow. Fibrous roots are affected first and they rot and die as the disease progresses to the main or tap roots, according to the North Carolina State University Extension. In tropical houseplants, the disease is caused by standing water left in the potting container. In outdoor tropical plants, the fungus travels through cool, wet soil. Plants are attacked in the spring when the soil is warming or in the fall during a period of wet weather. The fungus that causes root rot lives on both dead and live tissue. Prevent the disease by providing both indoor and outdoor plants well-drained soil and regular fertilization. Do not place tropical houseplants outside during cool, wet weather.
Fungal Leaf Spot
Fungal leaf spot affects tropical plants such as canna, plumeria and bougainvillea, according to the Clemson University Extension. Symptoms of fungal leaf spot vary with the fungus involved. In all types of fungal leaf spot, leaves are covered in spots that are dark in color, either gray or brown. The spots are often filled with the fruiting bodies of the fungus. Leaf spots may converge on a leaf, causing large areas of the leaf to die. Fungal leaf spots are not damaging to the tree although the leaves may fall before autumn. Fungal leaf spot is not damaging to otherwise healthy trees. Prevent by removing and destroying leaves, both on the tree and around the base of the tree to minimize recontamination the next spring.
Bacterial Leaf Spot
Bacteria such as xanthomonas also called leaf spot. Tan or brown angular spots surrounded by a yellow ring develop on the leaves. There are no fruiting bodies in bacterial leaf spot, according to the Missouri Botanical Garden. Bacteria enters through a wound or natural opening on the plant. This bacteria moves from plant to plant through the soil, by insects, in the wind or from plant debris. Treatment and prevention include destroying diseased plants, cover infected soil with mulch, water the roots and stem only and use only healthy plants. Bactericide treatments are not effective on every plant.