• Moshe Bar-Joseph, 
• David Ezra, 
• Grazia Licciardello  
• Antonino Catara 

Citrus fruits, consumed both fresh and as juice concentrate, are responsible for the world’s largest fruit tree industries. Among the cultivated Citrus species and hybrids, the etrog citron (Citrus medica L.) is one of the smallest crops, in both the size of its commercially cultivated areas and its limited geographic distribution. Furthermore, etrogs represent a specialty fruit crop, used mainly in traditional medicine and as a culinary interest for certain ethnocultures, and for the Jewish religious ritual of the week of Sukkot (tabernacle). Despite their uniqueness among edible citrus fruit, etrog trees share almost the entire range of susceptibilities to pests and disease agents that affect other citrus crops and may therefore host inoculum sources that will affect neighboring commercial citrus groves. This chapter provides a short historical account of some of the major epidemic diseases of the world's citrus industries and their impact on etrog citron cultivation.