Begonias are plants that can be found in tropical and subtropical areas of the world. The begonias are usually grown because they have attractive leaves, according to the University of Florida's website. However, there are a few diseases that can be devastating to begonias, leading often to leaf drop and death.
According to begoniacare.net, begonias do not always need fertilizer, since these plants can survive well with minimal fertilizer. Fertilizing might be beneficial in nutrient-poor areas, but this fertilizer should be added very lightly. The best way to keep begonia soil healthy is to add peat moss.
One of the worst things that can be done to the begonia is to over-water it, according to begoniacare.net. By over-watering the begonia, causing the begonia to stand in water, the begonia can be very susceptible to root rot, mildew and a variety of different viruses. The best way to prevent this over-watering problem is to make sure that the begonia soil is not drenched but is instead only moist.
A really common kind of fungus that occurs with the begonia is the powdery mildew, according to Cornell University. This mildew can be devastating to the begonia, killing begonias even with a mild infection. The plant will experience leaf drop and grow very poorly when infected with the powdery mildew. The infection of the begonia can be detected when the gardener notices white or gray coating on the surface of the leaves on the begonia. This fungus grows much more rapidly during periods of high humidity.
A bacterial problem that can develop on the begonias is the bacterial leaf spot, according to the University of Florida. The infection creates symptoms that are so faint that many gardeners do not even notice that the begonia is infected. Part of the begonia's leaf can die and the begonia leaves can develop speckling. This bacteria can infect all kinds of begonias. This bacteria usually cannot be destroyed and the begonia is best disposed of to prevent the infection of other begonias.
According to Cornell University, when begonias take up too much water, faster than the water can be released through transpiration, the water pressure in the plant can become too great and can lead to blisters on the begonia. These blisters mostly form on the lower areas of the leaves and needles on the begonia. These bumps are white, tan or brown. This can cause the leaves to turn yellow, brown and drop. When too many leaves fall off, the begonias are will not be able to engage in sufficient photosynthesis.