Bananas are native to the Australian, Asian and Indo-Malesian tropics and have been used by humans as food for thousands of years. Today, they are the fourth most important world food crop, according to Traditional Tree, after rice, wheat and corn. In addition to food crops, banana plants are used for medicines, flavorings, rope, silage and smoking materials. They are affected by numerous pests and diseases.
Large colonies of cyclamen mites infest the undersides of leaves, causing leaves to develop brown spots and drop. Spray the leaves with a nozzle attached to a hose and follow with a dormant oil spray.
The coconut scale lives in colonies on the undersides of leaves and causes a raised, patchy yellow or brown discoloration. Ant colonies tend the scale and feed on the honeydew excreted by the scale. Treat both the scale and ant infestations by spraying with a dormant oil.
Black sigatoka or black leaf streak is a debilitating and highly contagious disease causing reddish brown streaks on the undersides of leaves initially. Later, the leaves develop elongated tan or gray spots with dark brown margins. Remove and destroy any diseased leaves and spray with a fungicide. Good cultural practices, such as good soil drainage, full-sun and air circulation can minimize damage.
Yellow sigatoka causes yellowish streaks that turn to gray spots with brown borders. Eventually, the leaves turn brown or gray and drop. Spray with a fungicide and destroy all affected leaves.
Leaf spot causes pale brown oval patches with a bright yellow halo. Treat this disease by removing dead leaves and spraying the tree with a fungicide.