Citrus Canker: The Pathogen and Its Impact

Fig. 47. Example of implementation of the sentinel tree survey method. The grid depicted by the red lines divides the one-square-mile into 144 subsections. Where possible, within each subsection a legal property is selected on which one or more citrus trees highly susceptible to citrus canker are located (depicted in green). The result is an irregular array of trees that can be resurveyed for new canker infections on a 30-day rotation.



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