Magnesium hydroxide is useful against canker sores (aphthous ulcer) when used topically. Brown rot causes blossom blight, twig blight; twig canker and fruit rot. It is also used as a mouthwash for canker sores and toothaches. In California, oaks are affected by the fungal disease foamy bark canker. Additional stem canker and dieback are caused by the pathogen. The plant has some susceptibility to leaf spots, blights, rusts and canker. The damage done provides a point of entry for fungal rots and canker. Parsnip canker is a serious disease of this crop. Australia has had three outbreaks of citrus canker; all three were successfully eradicated. Australia has had three outbreaks of citrus canker, all of which have been successfully eradicated. The decline was mostly due to canker, citrus greening disease, and hurricane damage. The species is susceptible to canker and Verticillium wilt when stressed. Some of the symptoms of stem canker are branch splitting, gummosis and bark blistering. Various other disorders are documented, including canker disease and shuck decline complex. Sometimes the tissue above the canker will die causing girdling of the stem.