Stem cankers on rough lemon and Citrus volkameriana were among the higher values of disease recorded. Introduction Pathogenic fungi are responsible for several diseases in Arizona citrus groves. One of these diseases, Alternaria fruit rot caused by the fungus Alternaria citri , is commonly found in many navel orange groves in Maricopa County. Annual fruit losses have been estimated to reach 0.5 box per tree. Consistent reduction of Alternaria fruit rot by timely application of fungicides has yet to be achieved.
Additional study is needed to develop a reliable disease management approach.
Coniophora brown wood rot has caused extensive destruction in mature lemon plantings in Yuma County. A considerable amount of knowledge has been gained concerning the biology of the pathogen, Coniophora eremophila . We know that this fungus grows best at temperatures that occur during the summer in Arizona. There does not appear to be a significant effect of rootstock on disease development in lemon trees. Natural infection is associated with wounds on lemon trees, including stress fractures where branches are cracked but not completely severed from the tree.