Scab in Citrus

A fungal pathogen causes Scab in citrus. Spores are produced on the surface of scab pustules which are spread by either wind or rain. These pustules are slightly raised and pink to light brown in color. Young foliar lesions superficially resemble young citrus canker and may have a slight water soaked margin. As fruit and leaf pustules develop, the small elevated pink spots become more defined and may form conical depressions nearby. As the pustules mature, they become warty and crack. Pustule color may progress to yellowish brown and eventually to a dirty grey. On lemons, tangerines, and sour orange, the growths are relatively raised. In contrast, on grapefruit the growths are flatter.