Dwarf banana trees are a member of the Musa genus that -- depending on the cultivar -- grows in U.S. Department of Agriculture plant hardiness zones 5 through 11. Like full-size banana trees, dwarf cultivars can develop brown bumps on the bark, leaves and fruit of the plant. Since diseases and insects can cause brown bumps to appear, it is important to identify the problem before treating.
The brown bumps on the bark of your dwarf banana tree are probably scale, an annoying insect that feeds on the cell content of plants. Their feeding can cause the leaves of the dwarf banana tree to discolor and drop from the branches. In extreme circumstances, a scale infestation can lead to defoliation, twig dieback, loss of vigor and stunted growth. Spraying the banana tree with ready-to-use dormant oil during the winter months will kill overwintering pest. If scales are a problem when the tree is actively growing, consider increasing the amount of predatory insects -- such as ladybugs -- that prey on scales and control their numbers naturally.
Leaf Spot Disease
Leaf spot disease is caused by various fungal pathogens that attack plants of all species including dwarf banana trees. Leaf spot disease generally presents itself as yellowish or brown dots or raised bumps on the leaf surface. In severe cases, the infected leaves may fall from the banana tree. Thankfully, leaf spot disease is rarely a serious problem and can usually be tolerated with no long-term damage. Fungicides are not usually warranted, according to the University of California Statewide Integrated Pest Management Program, and control relies on cultural care. This includes removing organic matter and debris from around the tree, avoiding overhead irrigation and improving soil drainage.
Anthracnose is a fungal disease that can attack at any stage of the banana tree growth. Infected flowers, leaves and fruit skin will develop large brownish patches covered in a crimson-colored growth. As the disease progresses, infected fruits can turn black and shrivel. Fungicides do little if anything to control anthracnose and once a plant is infected, not much can be done to treat the diseases. Removing infected parts of the dwarf banana tree can help prevent the disease from spreading. The best defense against anthracnose, however, is to prevention through proper care and good sanitation.
Black or yellow sigatoka is a damaging and contagious disease that results in grayish spots edged in dark brown on the leaves of the dwarf banana tree. Sigatoka is difficult to control, according to Iowa State University Extension, and control relies on good cultural care. Removing and destroying all diseased plant matter and ensuring the tree is growing in well-drained soil with good air circulation will help control and prevent sigatoka.
- Missouri Botanical Garden: Musa × Paradisiaca
- Missouri Botanical Garden: Musa Basjoo
- California Rare Fruit Growers: Banana
- National Horticulture Board: Banana Diseases
- University of California Statewide Integrated Pest Management Program: Leaf Spot Diseases
- University of California Statewide Integrated Pest Management Program: Anthracnose
- University of California Integrated Pest Management Program: Scales
- Iowa State University Extension: Banana -- Black Sigatoka Disease
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