Citrus Huanglongbing: The Pathogen and Its Impact

Fig. 28. Response surface representations of disease development and spatial spread of citrus huanglongbing disease in the Shantou Citrus Cooperative plantation near Shantou, Guangdong Province, PRC in 1986 (top) and again 1988 (bottom). Note high disease incidence was predominantly along the southern border of the planting in 1986 and apparently emanated from dooryard plantings immediately to the south. Subsequent spread was to the north in the direction of equipment and personnel travel along north-south oriented raised beds.



Image from Plant Health Progress article:
Citrus Huanglongbing: The Pathogen and Its Impact