Bougainvillea was discovered in 1768 by Admiral Louis de Bougainvillea on a voyage that took him to the vine's native habitat, Brazil. The bougainvillea vine is an evergreen that can be trained to grow in containers, hanging baskets or to stand up to three or four feet in height.
Fungal and Bacterial Leaf Spot
Fungal and bacterial leaf spot will appear as small, reddish brown spots on young leaves. The spots will grow into larger circular or irregularly shaped, darker spots. In dry conditions, they will progress slowly. In wet weather, they will spread much faster. The spots become lesions with a tan middle, surrounded by a dark, reddish brown margin. The edges of the leaves may become ragged. The bougainvillea will become defoliated in the most severe cases. Prevention is the best course of action. Make sure the plant gets enough air circulation to help keep the leaves dry. Do not allow the branches to overlap. Remove and dispose of any infected leaves or in severe cases, the whole plant.
The wrong balance of minerals can cause several diseases in the bougainvillea plant. Leaf spots that are yellow or tan on older leaves can be a sign of magnesium deficiency, especially in yellow varieties. This can also be caused by too much watering On new growth, it could be either a magnesium or iron deficiency. Stunted, pale young growth where the veins of the leaf stay green is another sign of an iron deficiency. When old leaves turn pale green and the veins red, and new growth is stunted, it is a nitrogen deficiency. The plant needs phosphorus when the veins turn to red or purple and the rest of the plant has a purplish look. Potassium deficiency is the problem when the edges of the old leaves turn purple and the tips brown. A zinc deficiency, which is rare, causes the same yellow or brown spots as magnesium, but the leaves will be twisted. It is a calcium deficiency if dead spots appear in young growth and the tips die. Applying a complete micro-nutrient blend will get the bougainvillea back in balance.
Diseases Caused by Insects
Insects can not only eat away the leaves of the bougainvillea, they can cause moldy fungus diseases. The green aphid feeds on the new plant tissue and sucks out the fluid. A large infestation can cause the leaves to curl, turn yellow and become distorted, and the plant growth to be stunted. Aphids also leave behind a sticky substance called honeydew that attracts other insects, turns black, and turns into sooty mold fungus.
Soft scale insects also secrete honeydew. They feed on the fluid-conducting tissues of the plant. Soft scales include black scale, brown soft scale and the mealy bug. It is the young scales that do the damage. The leaves will wilt, turn yellow and drop off early. Scales can also curl the leaves or ruin the flowers. Before planting a new bougainvillea, make sure none of the neighboring plants have any infestations. If they do, take care of them first. Make sure all infected parts of the plants are removed and destroyed.