Banana tree leaves that are turning yellow and dying indicate that the tree is not getting the nutrients it needs. Inadequate fertilization, poor-draining soil, overwatering and fungal infection are some of the common reasons a banana tree (Musa spp.) might lack nutrients. Fortunately, many of these causes require a simple fix. However, it may not be possible to save a banana tree infected by certain pathogens, including fusarium wilt.
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Banana tree leaves turn yellow and die when infected with fusarium wilt or mosaic virus or when the tree is grown in soggy or nutrient-depleted soil.
Nutrient Deficiencies Causing Yellow Leaves
Yellowing leaves often indicate a lack of certain nutrients in the soil. You can make some well-educated guesses about which nutrient deficiency is affecting your banana tree by paying attention to which leaves and leaf parts are turning yellow and dying. A soil test, however, will reveal the exact nutrient needs.
For example, a banana tree that lacks potassium will display yellow leaf margins or tips. A magnesium deficiency displays yellowing along the midsection of the leaf parallel to the central vein and the leaf edge. A nitrogen deficiency will cause general yellowing in older leaves first, whereas a sulfur deficiency causes new leaves to turn yellow before older leaves. If you see thin yellow strips perpendicular to the central vein, your banana tree could be deficient in iron, zinc, manganese or copper.
Too much of a particular nutrient can also cause problems in banana trees. The best way to properly balance soil nutrients is to conduct a soil test and only fertilize with the nutrients shown to be lacking. If the soil test shows that no deficiency exists, the soil pH may need adjusting, the soil may be slow to drain, or the tree may be overwatered. Too much water prevents the roots from harvesting nutrients from the soil.
Yellow Leaves From Fusarium Wilt
Aside from nutritional deficiencies, one of the most common afflictions causing yellow leaves in banana trees is fusarium wilt, which is caused by a fungus. The fungus enters through the roots and grows inside the channels that transport water and nutrients throughout the plant. The plant essentially starves, and the leaves turn yellow and die.
A banana tree infected with fusarium wilt will — as the name implies — looks wilted due to the lack of water reaching its leaves. The yellowing will progress from the oldest to newest leaves.
Unfortunately, there is no known cure for fusarium wilt. The best way to address this soil-borne disease is to plant resistant banana tree cultivars. Contact your local extension office to have your soil tested to diagnose fusarium wilt.
Banana Mosaic Virus
Banana mosaic virus, also called cucumber mosaic virus, causes yellow streaks in banana leaves perpendicular to the central leaf vein. In bananas, the mosaic virus typically does not cause leaves to curl or wilt. It's also possible for only a few banana leaves to turn yellow from this virus rather than all of them.
In that case, it's possible for the banana tree to survive despite a minor infection. However, mosaic virus can infect many other types of fruits and vegetables and is easily spread by pests such as aphids. There is no cure for plant viruses, so infected plants should be removed and discarded to protect other nearby plants.
Banana mosaic virus can look like an iron, zinc, copper or manganese deficiency. One clue for which to look is whether each yellow streak is uniformly yellow (deficiency) or interrupted with other shades of green (mosaic virus).